Category Archives: General Horticulture/Weeds

Bagging Apples for Insect and Disease Control

Producing high quality apples in home gardens can be challenging due to damage caused by insects (e.g., apple maggot, codling moth, plum curculio, stinkbugs) and fungal diseases (e.g., apple scab, cedar-apple rust, flyspeck, sooty blotch).  Many insects damage apples when they lay their eggs in developing fruit.  Insect larvae can cause

Bagging apples can reduce fruit damage due to insects and diseases. (Photo courtesy of Janet van Zoeren)
Bagging apples can reduce fruit damage due to insects and diseases. (Photo courtesy of Janet van Zoeren)

additional damage as they tunnel into the fruit.  Wind-borne fungal spores can land on fruit leading to infections that damage fruit, reduce fruit aesthetics or affect long-term storage.

Although insecticide and fungicide sprays can help control insect pests and diseases, regular spraying can be inconvenient and costly for homeowners.  A non-pesticide alternative for protecting fruit is to encase apples in bags that provide protective barriers against insects and fungal pathogens.

What do I need to bag my apples?  First, you will need some sort of bagging material.  This could be a household plastic or paper bag, or a commercially-produced bag designed specifically for apple bagging.  Perhaps the most convenient choice is a common plastic sandwich or quart-size zip-type bag.  Zip-type bags are effective, weather proof, economical, and readily available.  You will also need something (e.g., a twist tie, tape, string, staples) to secure the bags to your apples and a pair of scissors to cut a drainage hole in each bag.

When do I bag my apples?  Start bagging when fruits are approximately ½ to 3/4 inch in diameter.  Apples typically reach this size approximately two weeks after petal fall.  Thin each cluster of apples to a single fruit, keeping the largest, best-shaped fruit in the cluster.  Make sure that the apples you select have not already been damaged.  In particular, plum curculio can damage fruit and codling moth can lay eggs before fruit are large enough to bag.  You may want to consider using an insecticide spray between petal fall and bagging to prevent this early damage.

How do I bag my apples?  Place an apple in the bag of your choice with the top of the bag around the stem.  Carefully secure the bag with a twist tie, tape, string or staple without damaging the stem.  If using a zip-type bag, place the stem in the middle and close the seal to within one inch of the stem on each side.  Staple the bag on each side of the stem to ensure that the bag will remain secure all summer.

Use scissors to cut approximately one-half inch from one of the bottom corners of the bag. This will allow condensation that may form inside the bag to drain.

Leave plastic bags on all summer.  Paper bags may deteriorate and need replacement if there is excessive rain during the growing season.  In addition, paper bags should be removed a few weeks prior to harvest to allow proper fruit color to develop.

Bagging apples can help prevent damage due to insect pests such as codling moth (left) and diseases such as apple scab (right). (Photos courtesy of Christelle Guédot and the UW-Plant Disease Diagnostics Clinic).
Bagging apples can help prevent damage due to insect pests such as codling moth (left) and diseases such as apple scab (right). (Photos courtesy of Christelle Guédot and the UW-Plant Disease Diagnostics Clinic).

What should my apples look like after they have been bagged?  Because bags prevent insects and fungal spores from reaching fruit, most of your bagged apples should be in near perfect condition.  Fruit that you do not bag will likely be blemished from insects and disease.  Blemished fruits should be removed (whether they fall to the ground or remain attached to your tree) and destroyed by burning (where allowed), deep burying or hot composting.  Diseased leaves from your apple tree should be treated similarly once they fall from the tree in the autumn.  Properly disposing of blemished fruits and diseased leaves will help limit overwintering of insect pests and disease-causing organisms, thus reducing insect and disease problems the following growing season.

For more information on bagging apples for insect and disease control:  Contact your county Extension agent.

Improving Cranberry Pollination

Successful cranberry production relies on cranberry flowers being adequately pollinated.  This fact sheet discusses several strategies that can be used to optimize pollination.

Proper pollination is important for successful cranberry production. (Photo courtesy of Johnston's Cranberry Marsh & Muskoka Lakes Winery, Ontario, Canada).
Proper pollination is important for successful cranberry production. (Photo courtesy of Johnston’s Cranberry Marsh & Muskoka Lakes Winery, Ontario, Canada).

Increase and diversify plants attractive to pollinators.  Having both native pollinators and honeybees on your marsh serves as an “insurance policy” to promote good fruit set.  Providing diverse sources of nectar and pollen (e.g., through the use of a pollinator garden), will encourage native pollinators to establish themselves long-term near your marsh and improve the health of honeybee colonies.  When planning a pollinator garden, select a site that is sunny and 1/3 to one mile away from your marsh.  Some common native plants to consider for a pollinator garden are listed in the figure below, with their approximate bloom times.

Promote nesting habitats for wild bees.  Wild bees need places to build their nests.  Approximately 70% of native bees nest underground and need areas of bare, sandy or loamy soil to build their nests.  The remaining 30% build nests by tunneling into stumps or twigs, or by constructing nests in cavities (e.g., in mounds of tall grasses, in debris piles, or in deserted rodent nests).  Native pollinators typically travel from 1/8 to one mile from their nests to feed, so suitable nesting areas need to be within this distance of a marsh for the bees to contribute to cranberry pollination.

Several programs can assist with the costs of creating pollinator habitats.  These include the USDA Environmental Quality Incentives Program, the USDA Farm Service Agency, the Wisconsin DNR Land Owner Incentive Program and the Bayer Crop Science Feed a Bee Initiative.

 

LEFT: Approximate bloom times for plants that are recommended to be grown near cranberry marshes as a supplemental nectar and pollen source for cranberry pollinators. RIGHT: Approximate flight periods for major groups of bees (including native species) found in cranberry marshes. The pink columns in both graphs represent the approximate time of cranberry bloom.
LEFT: Approximate bloom times for plants that are recommended to be grown near cranberry marshes as a supplemental nectar and pollen source for cranberry pollinators. RIGHT: Approximate flight periods for major groups of bees (including native species) found in cranberry marshes. The pink columns in both graphs represent the approximate time of cranberry bloom.

Reduce pesticide exposureYou can optimize bee health by creating a pollinator protection plan that promotes:

  • Practicing integrated pest management (IPM). IPM, which involves monitoring for pests and using a variety of appropriate management strategies, is used by most Wisconsin cranberry growers.
  • Spraying when bees are least active. Most bees forage from early morning until shortly before sunset. Therefore, the best time to apply a pesticide, especially during bloom (if allowed by the pesticide label), is in the late evening or at night.
  • Limiting pesticide drift. Whether plants are blooming or not, using a boom sprayer allows for direct application of pesticides onto cranberry plants.  Other methods that can reduce pesticide drift include calibrating your boom to optimize spray pressure and volume, selecting drift-reducing nozzles, avoiding pesticides with small particles that easily drift, and spraying when winds are under 10 mph and when relative humidity is above 50%.
  • Using insecticides and fungicides that have a reduced risk for bees. See the table below for insecticides and fungicides that are least toxic for bees.
Class
(IRAC or FRAC code)
Example
Active Ingredient(s)
Example
Trade Names
Insecticides

(IRAC code)*

diamide (28) chlorantraniliprole Altacor
diacylhydrazine (18) methoxyfenozide

tebufenozide

Intrepid

Confirm

biological Bacillus thuringiensis Biobit, Dipel
Fungicides

(FRAC code)*

strobilurin (11) azoxystrobin Abound, Evito
chitin synthase inhibitor (19) polyoxin D zinc salt Oso
biological Reynoutria sachalinensis Regalia

*  Note that rotating Insecticide Resistance Action Committee (IRAC) classes and Fungicide Resistance Action Committee (FRAC) codes (modes of action) will help delay development of pesticide resistance.

Strengthen your working relationship with beekeepers.  Optimal cranberry pollination requires cooperation between grower and beekeeper.  In some cases, outlining expectations in a signed, written contract can be the best way to prevent misunderstandings.  Topics to consider and discuss with your beekeeper can include, but are not limited to:

  • Hive inspections. Inspecting a random sample of 10% of hives when they are brought onto a march can help ensure that hives are of high quality and contain healthy bees.  Ideally, a third party should conduct the inspections in the presence of both beekeeper and grower.
  • When bees are introduced onto a cranberry marsh and the duration of their stay are important factors in optimizing cranberry pollination, as well as for maintaining honeybee health.  Bees should be brought onto a marsh at around 15% bloom.
  • Hive placement. Within the limits of your bed layout and equipment needs, it is best to place hives in the center of a marsh or near marsh edges with wild habitat, but away from water reservoirs, as bees from hive near water seem to be less likely to visit cranberry plants.
  • Exposures to sprays. Be explicit about when, how and what may be sprayed during bloom.

For more information on improving cranberry pollination:  Watch for UW Extension bulletin A4155, “Practices to improve pollination and protect pollinators in Wisconsin cranberry” (available soon at https://learningstore.uwex.edu/), or University of Wisconsin Garden Facts XHT1213 “Pollinators” (available at https://pddc.wisc.edu/), or contact your county Extension agent.

How to Properly Prune Deciduous Trees

Why should I prune my trees? Pruning is important for a variety of reasons. Pruning can help control the size of a tree, direct growth, influence flowering or fruiting, or maintain plant health and appearance. Pruning can also increase the safety of a tree by removing broken, diseased, dead, or dying branches. In addition to pruning, selecting plants that are suited to your environment and location are very important. The ultimate height and spread, in addition to location of overhead power lines, should be taken into account when selecting trees for landscaping.

The three step method of pruning large limbs.
The three step method of pruning large limbs.

What should I prune?

  • Newly planted trees: Newly planted trees should not be pruned unless a branch is broken, diseased or dead. These trees need foliage to produce carbohydrates (sugars) that are then transported to the root system for initiation of new roots.
  • Young trees: After a young tree is established for two to five years, the tree can be pruned to encourage a well-branched canopy. Lower branches can be removed to raise the canopy, if desired. Scaffold branches to be maintained in the tree should be selected such that they are 12-18 inches apart, are evenly distributed around the trunk and have wide crotch angles. Remove no more than 13 of the total crown of a tree at one time. Young trees also need corrective pruning to remove crossing branches, double leaders, watersprouts, and root suckers.
  • Older trees: Older, established trees, if properly trained when young, require little pruning. These trees should never be topped as this leads to poor branch structure and increased limb breakage. Use the three-point method of limb removal for pruning large branches (see diagram above and description below). This method ensures proper pruning and closure of wounds. Contact a certified arborist to prune larger limbs and remove trees, particularly if the tree is close to power lines or buildings.

The 3-point method of proper pruning of large limbs

When doing any type of pruning, always use a sharp pruning saw for making pruning cuts. Also, be sure to disinfect your pruning tools with alcohol or a 10% bleach solution after each pruning cut to avoid spreading diseases.

  • Step one: Select the branch that you want to remove. On large limbs, the first cut should be 12 to 18 inches from the limb’s point of attachment. The pruning cut should be an undercut made 12 way through the branch (see diagram). This pruning cut is very important because it relieves weight from the branch collar and prevents accidental tearing of bark from the tree’s trunk when the limb is removed.
  • Step two: The second pruning cut should be made on the outside of the first cut (i.e., farther from the trunk). Cut all the way through the limb from the top down, thus removing the weight of the branch.
  • Step three: The final cut should be made next to the tree’s trunk outside of the branch collar. Cut from the top down and cut all the way through the remaining branch stub. The branch collar should be left intact. DO NOT cut the branch flush with the tree’s trunk. A proper cut avoids large wounds, and allows the tree’s wound to close quickly.

Should I use wound treatments? In general, wound treatments, such as tree paint or wound dressing, are not recommended. These compounds slow down wound closure and promote decay. One exception when wound treatments are recommended, is the case of oak trees that are pruned during the growing season. Using wound treatments on oaks is important to keep out insects that transmit the oak wilt fungus (see University of Wisconsin Garden Facts X1075).

When should I prune trees? Most deciduous trees should be pruned in late fall to winter. At this time of year, you can see the overall branch structure easily, and most insects and disease causing organisms are not active. Late fall/winter pruning is especially important for oak trees to help prevent spread of the fungus that causes oak wilt (see University of Wisconsin Garden Facts X1075). Late spring and summer are usually not good times of year to prune because disease pathogens are present and wound closure is slower. If you prune in late winter, some trees may bleed or ooze sap excessively in the early spring. The bleeding may be unsightly, but does not harm the tree. Examples of trees that bleed excessively are maple, willow, birch, walnut, beech, hornbeam, elm, and yellowwood.

Definitions:

  • Branch collar: the ring of trunk tissue that surrounds a lateral branch at the point of attachment to the stem.
  • Double leaders: two major, terminal growing points located at the top of the tree.
  • Root suckers: vigorous, upright, adventitious shoots that arise from latent buds below the graft union or at the base of the tree.
  • Scaffold branches: the large branches that form the main structure of the crown of a tree.
  • Topping: an improper pruning technique that reduces the height of a tree by removal of large branches back to larger primary branches. This technique is not recommended.
  • Watersprouts: vigorous, vertical, adventitious shoots that arise from latent buds above the ground or graft union on older wood.

For more information on pruning: See UW-Extension bulletins A1817, A1771, A1730 and University of Wisconsin Garden Facts XHT1013, XHT1015, or contact your county Extension agent.

Zinnias

What are zinnias? Zinnias are one of America’s most popular annual bedding plants, but have humble origins as descendants of nondescript wildflowers native to the southwest U.S., Mexico and Central America. The zinnia was named after the 18th century German botanist Dr. Johann Gottfried Zinn, who wrote the first description of small, weedy plants that he discovered in the Mexican deserts. These plants had dull purplish-red, daisy-like flowers with single petals surroundng a protruding cone. Early varieties of garden zinnias were introduced in the U.S. in 1796, with double forms appearing in the mid-1800’s. Interest in zinnias increased in 1920 when Bodger Seeds Ltd. introduced the dahlia-flowered varieties ‘Giant Dahlia’ and ‘California Giant’. These varieties had large, flat-flowered heads and multiple colors. ‘California Giant’ eventually won a gold medal from the Royal Horticulture Society of England.

Zinnias can be a bright-colored addition to any garden, particularly when planted in mass.
Zinnias can be a bright-colored addition to any garden, particularly when planted in mass.

Today, zinnias come in a wide variety of flower forms: single, semidouble, or double. Single-flowered zinnias have one row of petals and the center of the flower is exposed. Semidouble-flowered zinnias have many rows of petals and the center can still be seen. Dahlia-type zinnias (typically semidouble) have large, flat blossoms. Double-flowered zinnias have so many rows of petals that flower centers are hidden. There are several types. Beehive-types have small blooms with stacks of flat petals resembling small beehives. Button-types are similar but have flatter flowers. Cactus-types have twisted, bent petals with rolled edges.

Although there are more than a dozen species of zinnias, only a few species are regularly planted in gardens. Zinnia elegans is the most common. It grows up to three feet tall and has single or double flowers in pink, rose, red, cherry, lavender, purple, orange, salmon, gold, yellow, white, cream or light green. Flowers range in size from one to seven inches in diameter and can be solid-colored, multicolored or zoned. Flower shapes include round, domed or ball-shaped, as well as dahlia-like or chrysanthemum-like. Tetraploid varieties (having four sets of chromosomes, rather than the normal two) were developed in the 1950’s, and these varieties produce larger flowers on stronger stems, grow more vigorously and have increased disease resistance. Hybrid varieties were developed soon thereafter. There are many varieties of Z. elegans available at garden stores, including the following.

  • The Border Beauty series has plants that grow up to 20 inches tall and have 3½-inch-wide semidouble to double, dahlia-like flowers.
  • The Peter Pan series has dwarf hybrids that grow up to 12 inches tall and have very large (up to five-inch-wide), slightly curled, double flowers. Seven separate colors in this series have been recognized as All-American Selections (AAS) winners.
  • The Ruffles series was developed for cut flower production. Plants grow up to 30 inches tall and have 2½-inch-wide, ball-shaped flowers with ruffled petals on stiff, upright stems. ‘Scarlet Ruffles’ was named an AAS winner in 1974, ‘Cherry Ruffles’ and ‘Yellow Ruffles’ AAS winners in 1978.

Z. angustifolia (synonym Z. linearis) has small, single, golden-orange flowers with yellow stripes, and narrower foliage than Z. elegans. These compact plants grow eight to 12 inches high, and can spread to two feet. The variety ‘Crystal White’ has pure white flowers with yellow centers and was an AAS winner in 1997. A cross of Z. elegans and Z. angustifolia yielded the Profusion series of zinnias which has compact plants with two to three-inch-wide, single flowers. Members of this series have superior heat and humidity tolerance, and tend to be disease resistant. Two members of this series ‘Cherry Profusion’ and ‘Orange Profusion’ won gold medals from AAS in 1999 (the first awarded to flowers in 10 years).

Z. haageana (Mexican zinnia) grows up to 18 inches tall and has small 1½ to two-inch-wide flowers on long stems. Flowers may be single or double, solid or bicolor, in red, mahogany, yellow and orange. Two popular varieties may be available at your local garden center.

  • ‘Persian Carpet’ (an AAS winner in 1952) grows up to 15 inches tall and has two-inch-wide, double, bicolored flowers of gold, maroon, purple, chocolate, pink or cream;
  • ‘Old Mexico’ (an AAS winner in 1962) has bushy, compact, 18-inch-tall plants with double, 2½-inch-wide blooms of deep, rich mahogany highlighted with yellow-gold.

Z. pauciflora (synonym Z. peruviana) grows up to 30 inches tall and produces 1½-inch-wide, single, red or yellow flowers with button-like centers. This zinna is good for cutting and drying, and has powdery mildew resistance. Only varieties ‘Bonita Red’ and ‘Bonita Yellow’ are readily available.

Zinneas can be effectively used in gardens as an edging plant.
Zinneas can be effectively used in gardens as an edging plant.

Where do I get zinnias? Zinnias can be purchased as bedding plants, but local garden centers often have only a limited selection of varieties. As an alternative, zinnias can be started from seed, either indoors four to six weeks before the last expected spring frost, or directly in the garden when the soil warms sufficiently. Germination takes five to seven days. Many references warn that zinnias do not like being disturbed and should not be moved after seeding. However, plants can be seeded individually in cells of seed-starting trays or even transplanted into these cells from mass plantings. When transplanting into trays, wait until the first true leaves have emerged. Separate roots as carefully as possible and place seedlings into their new cells up to the first set of leaves (the seedling leaves). Select appropriately sized tray cells based on the predicted size of the varieties being grown. Otherwise, tall varieties may outgrow their cells before it is time to plant them outdoors. Once the danger of frost has passed, zinnias can be transplanted outside. However, do not expect substantial growth until temperatures are above 50°F.

How do I grow zinnias? Zinnias do best in full sun in fertile, well-drained soil. Space plants four to 24 inches apart depending on variety. When growing zinnias for cut flowers, crowd plants to encourage longer stems. To produce bushier plants, pinch the tops out of plants when they are four to six inches high. Remove faded blossoms to encourage new blooms. Plants should be kept well-watered and fertilized two times per month for optimum bloom. Most varieties begin to bloom when very young and continue to bloom until frost.

Zinnias have few insect pests, but occasionally can have problems with aphids (see University of Wisconsin Garden Facts XHT1043), four-lined plant bugs (see University of Wisconsin Garden Facts XHT1101) and spider mites. Common diseases of zinnias include powdery mildew (see University of Wisconsin Garden Facts XHT1005), Alternaria leaf spot and bacterial leaf spot.

How do I use zinnias most effectively in my garden? Zinnias make good edging plants, but are also effective when grown in masses. Taller varieties make good background plants in flowerbeds, while smaller varieties are suitable for container plantings. Zinnias are great additions to butterfly gardens and many varieties make excellent cut flowers.

For more information on zinnias: Contact your county Extension agent.

Zebra Iris

What is zebra iris? Zebra iris (Iris pallida), also known as sweet iris, Dalmatian iris or variegated iris, is a very old garden plant. It is native to rocky areas of northern Italy and the eastern Mediterranean including Dalmatia, a province of Croatia (hence one of the plant’s common names). Zebra iris was one of the primary species used in the development of the tall bearded iris. Dried zebra iris root (along with the roots of other species of iris) is a source of orris root powder. This powder was used medicinally (and for its supposed magical and alchemical properties) in medieval times, as well as a perfume and potpourri fixative for many centuries. Roots may require several years of drying before fully developing their fragrance. Orris oil (derived from fresh roots) is used as a flavoring in soft drinks, candies and chewing gum.

Zebra iris produces clumps of sword-like leaves.  Several varieties have striped foliage.
Zebra iris produces clumps of sword-like leaves. Several varieties have striped foliage.

Zebra iris produces low clumps of sword-like leaves that remain nearly evergreen in areas with mild winters, but die back to the ground in colder climates. The original color of the foliage of this species was a solid bluish-green. Newer cultivars of zebra iris have leaves with vertical stripes of blue-green and either silvery-white (varieties ‘Alba-variegata’ and ‘Argentea Variegata’) or creamy yellow to pale gold (varieties ‘Aurea-variegata’ and ‘Variegata’).

Zebra iris cultivars are grown primarily for their attractive striped leaves, although in early summer they do produce pretty, lavender-blue flowers with small, yellow beards on three-foot-tall scapes. The tall branched flower stems may need staking in windy, exposed areas. The highly fragrant flowers have a distinctive scent that has been variously described as reminiscent of grape jelly, orange blossom, or vanilla. Zebra iris is hardy in zones 4 through 9.

Where do I get zebra iris? Zebra iris plants can be purchased at local nurseries and garden centers. Once established, clumps should be divided as needed every three to four years after flowering has occurred, just as you would a bearded iris.

How do I grow zebra iris? Grow zebra iris in full sun and well-drained soil for best results. However, zebra iris will tolerate more shade than many bearded irises do, and will also thrive in heavy clay and medium clay loam soils. When planting zebra iris, place rhizomes partly above the soil and keep newly transplanted plants well-watered. Once established, zebra iris is somewhat drought tolerant and require little maintenance. Simply remove old foliage before new leaves emerge in early spring. Note that varieties with gold leaf coloring appear to be more vigorous than those with white leaf coloring.

Zebra iris has few pests. Rabbits and deer rarely bother this plant and iris borer (see University of Garden Facts XHT1041) is much less of a problem than on bearded iris.

Zebra iris produces lavender-blue flowers with small yellow beards.
Zebra iris produces lavender-blue flowers with small yellow beards.

How do I use zebra iris most effectively in my garden? The striking foliage of zebra iris makes a great accent in a sunny perennial border, especially near the front. The stiff upright form of zebra iris offers good contrast to mounded shapes, while the dramatic coloring of striped varieties stands out among solid-colored foliage, particularly purple-leaved plants. Interplant with low, open perennials or taller ramblers such as pincushion flower (Knautia macedonica). Zebra iris also pairs nicely with traditional perennials such as fern leaf yarrow (Achillea ‘Moonshine’), purple coneflower (Echinacea spp.) and ‘Husker Red’ beard-tongue (Penstemon ‘Husker Red’), and is a good companion with Arkansas bluestar (Amsonia hubrechtii). Or use zebra iris as a neat edging in larger plantings. Zebra iris is a natural around water and really stands out in rock gardens. It can also be stunning in suitable containers.

For more information on zebra iris: Contact your county Extension agent.

Yellow Corydalis

What is yellow corydalis? Yellow corydalis (Corydalis lutea = Pseudofumaria lutea) is a shortlived perennial in the bleedingheart family (Fumariaceae). The genus Corydalis has approximately 300 species, and the name derives from the Greek ‘korydalis’ meaning crested lark, a reference to the fact that the plants’ flowers resemble a lark’s head. Other common names of yellow corydalis include yellow fumitory, hollowort, and yellow larkspur. Native to the southern Alps of Europe, this plant is hardy in zones 4 through 8.

Yellow corydalis plants have finely cut foliage with yellow, tubular flowers.
Yellow corydalis plants have finely cut foliage with yellow, tubular flowers.

Yellow corydalis plants form neat mounds of finely cut, delicate-looking light-green to blue-green foliage, somewhat resembling the foliage of maiden hair ferns or bleeding hearts. The pinnately compound leaves have three lobes, and are pale green above and glaucous (i.e., waxy) below. The leaves are borne on weak, hollow and fleshy stems. Plants grow up to 18 inches tall, but often are much shorter.

In mild climates, yellow corydalis remains evergreen (although not necessarily attractive), but in climates with colder winters, dies back to the ground. In very hot summers or during drought, plants may also die back, but they often resume growth in the fall when cooler, moister conditions prevail. In Wisconsin’s relatively cool climate, when planted in a moist site, yellow corydalis does not die back at all. This is in contrast with the majority of other Corydalis species that are more easily heat-stressed and prone to dieback.

As its name suggests, yellow corydalis produces bright, golden-yellow flowers. It blooms over a long period, from late spring through frost. The one to two inch long flowers have four petals arranged in an irregular tubular shape with a spur in the back. Flowers are borne in racemes of six to 16 flowers on stems that rise above the foliage. Slender, dehiscent capsules (i.e., seed pods that naturally break open along a seam) follow the flowers. Capsules eventually burst to scatter their seed.

In addition to C. lutea, there are other Corydalis species with yellow flowers that are suitable for use in the garden.

  • C. aurea (hardy to zones 3 through 8) is known as scrambled eggs and is a biennial that produces small flowers in the spring of the second year of growth.
  • C. cheilanthifolia (hardy to zones 4 through 9) has fern-like leaves and upright, butter-yellow flower clusters. The leaves become bronze in the fall.
  • C. ochroleuca (hardy to zones 5 through 8) has blue-green leaves, with creamy yellow-white flowers with green lips and yellow throats.

While useful as an ornamental, yellow corydalis does have one potentially problematic characteristic. It is toxic to horses, causing mouth sores, gingivitis, colic and sudden death (if enough is ingested). Therefore, yellow corydalis should not be allowed to invade pastures.

Yellow corydalis makes an excellent border plant.
Yellow corydalis makes an excellent border plant.

Where do I get yellow corydalis? Yellow corydalis plants are available at many nurseries and garden centers that stock perennials. Once established in the garden, this plant tends to self-seed prolifically, and can become somewhat weedy in certain conditions, although it is easily removed where not wanted. Yellow corydalis commonly establishes around stone walls or in gravelly soil. Seedlings can be transplanted in early spring. However, established plants often do not perform well if moved. If you do transplant yellow corydalis, plants will require extra watering and will often struggle for the remainder of the season. Yellow corydalis plants are also not easily divided, but divisions can be made in early spring. Although it self-seeds readily, yellow corydalis is not easy to germinate indoors due to its complex dormancy requirements. To germinate the seeds, sow them in a moist potting medium, then place them in a plastic bag and keep at room temperature (approximately 70ºF) for six weeks. Move the seeds to near freezing conditions (28 to 38ºF) for six to eight weeks, then return to cool conditions (50 to 60ºF). If there is no germination after several weeks, repeat the heating and cooling steps a second time.

How do I grow yellow corydalis? Yellow corydalis grows well in either sun or light shade. It prefers well-drained soil and does best with good moisture during hot weather. However, it does not tolerate wet soils during winter. Yellow corydalis likes ordinary to rich, humusy soil, but tolerates drier, gravelly soil and sandy loam to clay as well. In heavier, wetter soils, shallow planting may help yellow corydalis survive Wisconsin’s harsh winters. Yellow corydalis is relatively insect pest and disease-free.

How do I use yellow corydalis most effectively in my garden? Yellow corydalis can be extremely attractive when used to edge borders or walkways. In rock gardens, cottage and woodland gardens, it is a good filler and may naturalize. It will grow well in stone walls in cool conditions. Yellow corydalis combines well with bleeding heart (Dicentra spectabilis), lady’s mantle (Alchemilla mollis), lungwort (Pulmonaria spp. – See University of Wisconsin Garden Facts XHT1174), foam flower (Tiarella spp.), hosta (Hosta spp.), leopard plant (Ligularia spp.), and many other perennials in a shade garden. Try yellow corydalis in sunny areas under taller plants like peonies (Paeonia spp.) or daylilies (Hemerocallis spp.).

For more information on yellow corydalis: Contact your county Extension agent.

Wood Mulch and Tree Health

What are the benefits of wood mulch? Wood mulch is typically available as chipped wood, or shredded or chunked bark, and can contribute to tree health in many ways. When high quality, composted mulches are applied two to four inches deep in a ring three to six feet in diameter (or greater) from the trunk of a tree, mulch can help preserve moisture, control weeds, limit damage to the trunk from mowers and string trimmers and moderate the soil temperature. Use four inches of mulch when soils are light and well-drained, and two inches of mulch on heavier, clay soils.

Use of properly composted mulches can be beneficial to trees and shrubs in the landscape.
Use of properly composted mulches can be beneficial to trees and shrubs in the landscape.

Can wood mulch harm trees? Use of improperly composted mulches (some-times called “sour mulches”), can lead to tree nutrient deficiencies. Sour mulches can also produce gases like methane and ammonia that can be toxic to plants. Foliage on trees surrounded by sour mulches may initially turn yellow, then brown, die and fall off. If your mulch smells like vinegar, ammonia or sulfur, it is likely a sour mulch, and should be removed. Replace the sour mulch with a high quality, composted mulch and consult with your local UW-Extension agriculture/horticulture about testing the soil for nutrient deficiencies. Fertilize appropriately based on the results of these tests.

Improper application of mulch can also lead to problems. Piling wood mulch up against the trunk of a tree can keep the bark underneath excessively wet. This wetness can contribute to bark decay. In addition, use of thick mulch layers (greater than four inches) can lead to overly wet soils that are favorable for development of root rots (see University of Wisconsin Garden Facts X1070). To avoid these problems, make sure mulch is applied at least one to two inches away from the trunk of the tree and that the mulch layer is the appropriate thickness for the soil type in your landscape (see above).

Does woody mulch harbor or attract insects? Insects such as earwigs (see UW-Extension bulletin A3640), centipedes (see University of Wisconsin Garden Facts X1113), millipedes (see University of Wisconsin Garden Facts X1108) and sowbugs (see University of Wisconsin Garden Facts X1110) can feed on decaying organic matter in mulches. While these insects are often only nuisances, earwigs can feed on and cause damage to a variety of ornamentals, particularly to flowering plants. If mulch is used near entrances to a home or around basement windows, these unwanted insects may get inside.

Termites ingest wood and can be attracted to wood mulch, but new termite colonies are not likely to become established due to use of wood mulches. Typically termites are not a problem in Wisconsin, and when colonies are found, they occur only in the southern half of the state.

Carpenter ants (see UW-Extension bulletin A3641) and powderpost beetles (see University of Wisconsin Garden Facts X1053) are unlikely to utilize mulch as a food source because conditions required for their development would not be satisfied by wood mulch. Carpenter ants do not ingest wood as a food source; instead, they chew non-living wood (in trees or landscape timbers, etc.) to excavate galleries in which they live and raise their young. Since wood mulch is composed of small wooden pieces, it would not serve as a home. To avoid potential insect problems, keep mulch as far away from the foundation of your home as possible and seal all holes and crevices where insects might use as entry points. Also, periodically inspect landscape timbers and the house for termites.

Does woody mulch harbor tree pathogens? Wood mulch may come from many sources, including trees and shrubs that have died from a wide range of diseases. To be harmful to your trees, disease-causing organisms (pathogens) would have to survive in mulch and these organisms would have to move from the mulch either directly, or through the soil, to their new host – your tree. There is currently very little research on this topic.

Elm trees killed by Dutch elm disease (see University of Wisconsin Garden Facts X1076), can serve as breeding areas for native and European elm bark beetles. Bark beetles that breed in logs or firewood from these trees can pick up the fungi that cause Dutch elm disease (Ophiostoma ulmi and Ophiostoma novo-ulmi) and carry these fungi from tree to tree. Chipping infected elm trees creates an unfavorable environment for bark beetles yet there is no scientific literature that describes the level of risk of transmitting the Dutch elm disease fungi from wood chips or bark chunks to healthy elms.

Oak trees killed by oak wilt (see University of Wisconsin Garden Facts X1075) can be attractive to several sap-feeding beetles that can potentially pick up the oak wilt fungus (Ceratocystis fagacearum) and move it in the landscape. This process is affected by moisture and temperature and would likely be disrupted by the chipping and composting process yet there is no scientific literature that describes the level of risk of transmitting the oak wilt disease fungus from wood chips or bark chunks to healthy oaks.

Recent research at the University of Wisconsin-Madison suggests that wood chip mulches produced from trees suffering from Verticillium wilt (see University of Wisconsin Garden Facts X1008) can serve as a source of the fungus (Verticillium dahliae) that causes the disease. These studies show that Verticillium can survive for at least one year in mulch and that use of this contaminated mulch can lead to Verticillium wilt in both woody and herbaceous plants. Therefore use of mulches produced from trees with Verticillium wilt should be avoided.

For more information on proper tree care: See UW-Extension Bulletin A1817, or contact your county Extension agent.

Wisconsin Lawn Care Calendar

Regular care and maintenance will yield a lawn that is lush and beautiful.
Regular care and maintenance will yield a lawn that is lush and beautiful.

The following lawn care calendar provides an overview of home lawn maintenance. Not all lawns require every maintenance activity. Be sure to customize the care of your lawn to its specific problems and needs. For details on specific activities listed below, check out the University of Wisconsin-Extension bulletins (available at http://learningstore.uwex.edu) and University of Wisconsin Garden Facts (available at http://hort.uwex.edu) that are referenced at the end of this fact sheet. Finally, be sure to read and follow all label instructions of any pesticides that you select to ensure that you use these products in the safest and most effective manner possible.

April

  • Rake and clean up winter debris as weather allows.
  • Reseed bare spots, and establish a new lawn, if you desire.
  • Apply a pre-emergent crabgrass herbicide to your established lawn.
  • Mow your lawn to remove 1/3 of the current grass height. Grass should be 21/2 to 31/2 inches tall after mowing.

May

  • After your grass is actively growing, core aerate your lawn if the thatch layer is over one inch thick.
  • Late in May (e.g., around Memorial Day), fertilize your lawn using a controlled-release or slow-release formulation. For grass growing in the sun, use the label rate of the fertilizer that you have selected. For grass growing in the shade, apply half of the label rate.
  • Apply an herbicide to your established lawn to control actively growing broadleaf weeds. DO NOT use herbicides on newly seeded areas. If possible, apply the herbicide to weeds when they are blooming. Many fertilizer products also contain herbicides for broadleaf weed control, so combining fertilizer and herbicide applications may be possible.

June

  • If you have not applied one previously, apply an herbicide to your lawn for broadleaf weed control.
  • Begin watering your lawn as needed for the summer. Or alternatively, do not water and allow the lawn to go dormant (i.e., turn brown) if natural rains are insufficient.
  • Watch for insect pests, diseases, and other lawn problems.

July

  • Water your lawn as needed. If you do not water, your lawn will naturally go dormant.
  • Early in July (e.g., around Independence Day), fertilize with a controlled-release or slow-release fertilizer. For grass growing in the sun, use the label rate of the fertilizer that you have selected. For grass growing in the shade, apply half of the label rate. If your lawn has been consistently fertilized for 10 to 15 years, if you leave clippings on your lawn when you mow, or if your lawn has gone dormant, skip this application.
  • Apply a grub control product to your lawn if there is a history of grub problems and/or your lawn is a high maintenance (i.e., regularly watered) lawn.
  • Avoid seeding and spraying for weeds.
  • Watch for insect pests, diseases, and other lawn problems.

August

  • Water your lawn as needed.
  • Establish a new lawn or renovate your current lawn. Note that mid-August to mid-September is the best time to establish a lawn in Wisconsin.
  • Watch for insects, diseases, and other lawn problems.

September

  • Early in September (e.g., around Labor Day), fertilize your lawn using a controlled-release or slow-release formulation. For grass growing in the sun, use the label rate of the fertilizer that you have selected. For grass growing in the shade, apply half of the label rate.
  • Apply an herbicide to your established lawn to control broadleaf weeds. Fall is the best time to apply herbicides for weed control. DO NOT apply herbicides to lawns planted in August or September.
  • Core aerate actively growing lawns if the thatch layer is over one inch thick, or if the soil is compacted.

October

  • Apply a broadleaf herbicide to your lawn if you did not apply one in September and the weeds are still growing.
  • If you have removed clippings from your lawn all season, fertilize your lawn in early October using a controlled-release or slow-release formulation. For grass growing in the sun, use the label rate of the fertilizer that you have selected. For grass growing in the shade, apply half of the label rate.

November

  • Continue to mow your lawn until it goes dormant for the winter.

For more information on lawn care and lawn pests: See University of Wisconsin-Extension bulletins A1990, A2303, A3179, A3237, A3271, A3275, A3434, A3435, A3700, A3710, and A3714 (available at http://learningstore.uwex.edu), and University of Wisconsin Garden Facts XHT1018, XHT1023, XHT1062 and XHT1114 (available at http://hort.uwex.edu), or contact your county Extension agent.

Wild Parsnip

What is wild parsnip? Wild parsnip (Pastinaca sativa) is an aggressive Eurasian member of the carrot family that grows in sunny areas and tolerates dry to wet soil types. It is often found along highways, in prairies or bordering farmed fields. The plant spreads primarily by seed. Sap from the plant can cause phytophotodermatitis, a light sensitive reaction on your skin. If the juice from broken stalks, leaves or flowers contacts your skin and then is exposed to sunlight, a skin rash will result 24-48 hours later. Symptoms range from slightly reddened skin to large blisters. The blisters may produce a sensation similar to a mild to severe sunburn. The blisters do not spread or itch, as poison ivy rashes do, but they are uncomfortable and leave brown scars that last for a number of months to two years. See your doctor if you develop burn symptoms.

A wild parsnip plant.
A wild parsnip plant.

What does wild parsnip look like? At maturity, wild parsnip is about four to five feet tall. It bears many large flat clusters of yellow-green flowers on a thick stem. Flowers appear from the first of June through July in southern Wisconsin. Seeds form around the end of July. The plant will often have both flowers and seed capsules at the same time. Seeds are flat, oval and about the size of a sunflower seed. After flowering and producing seed, the plant turns brown and dies. The plants have a rosette of basal leaves, as well as leaves arranged alternately on the stem. The leaves are branched into leaflets and have heavily toothed margins. The plant can be confused with prairie parsley (Polytaenia nuttallii), an endangered native species in Wisconsin. Prairie parsley has sparse, light yellow flowers, and long leaves branched into leaflets with few teeth.

How can I control wild parsnip? Prevention is the best way to control wild parsnip. When wild parsnip is first detected in an area, it can be cut below ground level with a sharp shovel. Be sure to wear long sleeves, long pants and gloves when working with plants. Also, try to work after sunset so that exposure to sunlight does not occur. Plants can also be pulled by hand, if you wear protective gloves. If the wild parsnip population is fairly large, you may use a brush-cutter just after peak bloom and before the plant sets seed. Remove all the cut material. A few weeks later, repeat the treatment to prevent plants from re-sprouting. Treatments may need to be repeated over several years. Herbicides containing the active ingredient glyphosate are also effective against wild parsnip. In high quality natural areas such as prairies, the Department of Natural Resources recommends burning the site and then applying spot treatments of a 1-3% glyphosate solution to wild parsnip rosettes if they re-sprout after burning.

For more information on wild parsnip: See the DNR publication ER-090-97 – “Wisconsin Manual of Control recommendations for Ecologically Invasive Plants”, or contact your county Extension agent.

 

Using Crop Rotation in the Home Vegetable Garden

What is crop rotation? Crop rotation is one of agriculture’s oldest cultural practices. In a home vegetable garden, crop rotation involves changing the planting location of vegetables within the garden each season. Crop rotation is used to reduce damage from insect pests, to limit the development of vegetable diseases, and to manage soil fertility.

Use of crop rotation can lead to a healthier, more productive garden.
Use of crop rotation can lead to a healthier, more productive garden.

Why is crop rotation important? Each vegetable can be classified into a particular plant family. Plants belonging to the same family oftentimes are susceptible to similar insect pests and diseases, and have similar nutrient requirements. When vegetables classi­fied in the same plant family are grown year after year in the same area of a garden, they provide insect pests with a reliable food source and disease-causing organisms (i.e., pathogens) with a continual source of host plants that they can infect. Over time, insect pest and pathogen numbers build in the area and damage to vegetable crops increases. Using crop rotation helps keep insect pest and pathogen numbers at low levels. In addition, the type of vegetable grown in a particular area in a garden has a direct effect on the fertility of the soil in that area. Each vegetable is unique in the type and amount of nutrients it extracts from the soil. Crop rotation can even out the loss of different soil nutrients and allow time for nutrients to replenish.

How do I plan a crop rotation for my home garden? Plan the crop rotation for your vegetable garden based on the types of vegetables that you grow. Vegetable crops in the same plant family should NOT be planted in the same area of a garden year after year. For example, if tomatoes are planted in a bed or area of a garden one year, vegetable crops such as peppers, eggplant, potatoes and tomatoes should not be planted in the same bed or area the following year because all of these plants belong to the nightshade family (Solanacaeae). Table 1 provides a guide to common garden vegetables and their plant families.

Crop rotations vary in complexity. They can be as simple as changing vegetable locations annually, or can be extremely involved, using cover crops/green manures, and/or leaving parts of a garden fallow (i.e., planting nothing in an area) each year. Cover crops/green manures are planted before, after or in place of a vegetable crop to improve soil fertility and drainage, prevent erosion, and hold nutrients. See University of Wisconsin Garden Facts XHT1209, “Using Cover Crops and Green Manures in the Home Vegetable Garden” for details. Leaving an area fallow is often less desirable than planting a cover crop/green manure because an area without a planted crop tends to be more prone to erosion and can end up with a soil that does not drain properly. Alternatively, the area may become filled with weeds that will cause problems for future vegetable production.

For crop rotation to be most effective, DO NOT plant an area with vegetables or cover crops/green manures from the same plant family more than once every three to four years. This length of crop rotation can be difficult to achieve in small gardens, but even changing plant families grown in an area of a garden from year to year is helpful in managing insect pests and diseases. To help in planning crop rotations, keep a garden log or map as a reminder of where vegetables are planted each year.

Table 1. Common vegetables and their plant family classifications.

PLANT FAMILY VEGETABLE
Carrot Family
(Apiaceae)
Carrot, celery, parsley, parsnip
Goosefoot Family
(Chenopodiaceae)
Beet, spinach, Swiss chard
Gourd Family
(Cucurbitaceae)
Cucumber, muskmelon, pumpkin, summer squash,
watermelon, winter squash,
Grass Family
(Poaceae)
Ornamental corn, popcorn, sweet corn
Mallow Family

(Malvaceae)

Okra
Mustard Family
(Brassicaceae)
Broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, collard, kale, kohlrabi, mustard greens, radish, rutabaga, turnip
Nightshade Family
(Solanaceae)
Eggplant, pepper, potato, tomato
Onion Family
(Alliaceae)
Chives, garlic, leek, onion
Pea Family
(Fabaceae)
Bush bean, kidney bean, lima bean, pea, pole bean, soybean
Sunflower Family
(Asteraceae)
Endive, lettuce, sunflower

For more information on using crop rotation in the home vegetable garden: Contact your county Extension agent.

Thanks to Diana Alfuth, Steve Huntzicker, Mark Kopecky and Erin Silva for reviewing this document.