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April: Winter Injury

Temp changeThis past winter’s weather was a roller coaster ride of seasonably cold temperatures in December and January, followed by record warm stretches in February, followed by cold temperatures again for much of March. These extreme temperature fluctuations can injury many woody landscape plants.

The Most Typical Forms of Winter Weather-related Plant Injury

Cold injury

Cold injury is a physical damage to plants due to cold temperatures.  Fruit trees (e.g., apples, pears, cherries, plums and especially peach and apricot) are particularly prone to this problem.  Plants can suffer from cold injury in the fall if temperatures stay relatively warm and then precipitously plummet, not allowing plants enough time to properly harden off for the winter.  Cold injury can also occur in the middle of the winter if there are extended warm periods where plants break dormancy, followed by cold temperatures that kill actively growing tissue.  Finally cold injury can occur in the spring if plants leaf out and then are exposed to an unexpected frost.  Trees and shrubs with cold injury typically have scattered branches that never leaf out, or scattered branches where leaves emerge and then shrivel, dry up and die.  In extreme cases, cold injury can kill an entire tree or shrub.  Cold injury in apples and pears is often misdiagnosed as fire blight.

Winter burn

Winter burn occurs when trees or shrubs (e.g., yew, Alberta spruce and boxwood) run out of internally stored water and dry out.  Winter burn can occur during the winter, but most often is noticeable as trees and shrubs break dormancy.  Browning of needles (e.g., on yew) or bleaching of leaves and stems (e.g., on boxwood) are characteristic symptoms.  Winter burn can affect just a few branches (which in some cases eventually recover) or an entire plant (which in some cases may die).

How to Minimize the Effects of Winter Injury

Choose hardy plants

Consult the USDA plant hardiness zone map to determine your hardiness zone and select plants that are rated to survive in your climate.

Plant marginally hardy plants in protected areas

You can still try to grow your favorite marginally hardy trees and shrubs, but plant these near your house, particularly in sheltered areas that may be slightly warmer than the rest of your yard.

Plant at the right time of year

Plant in the spring or late summer (August or September) to allow for root growth before the onset of winter and to avoid hot mid-summer temperatures that can be stressful on new transplants.

Mulch properly

Mulch around trees and shrubs out to their driplines, keeping mulch at least three inches from the bases of plants.  Use one to two inches of a high quality mulch (e.g., shredded oak bark mulch) on heavier, clay soils and three to four inches on lighter, sandier soils.  Proper mulching can help insulate roots over the winter.

Water properly

It is particularly important to water evergreens into the fall up until the ground freezes or there is a significant snowfall.  This will help prevent winter burn.  Established trees and shrubs require approximately one inch of water per week; newly transplanted trees and shrubs requite up to two inches of water per week.  If supplemental watering is needed, use a soaker or drip hose; Do not use a sprinkler.

Fertilize properly

Do not fertilize trees and shrubs in late summer and fall.  Fertilizing late stimulates growth that is more likely to be injured as temperatures drop in the fall.

Prune properly

Avoid pruning in later summer and fall.  Late pruning on some trees and shrubs can stimulate growth that is more likely to be injured by cold fall temperatures.

Protect plant for the winter

Build barriers (e.g., of burlap or canvas) around sensitive plants to deflect and reduce the drying effects of winter winds.

For more information on winter injury/winter burn and additional specifics on how to prevent winter injury/winter burn from being a problem, see the University of Wisconsin Garden Facts “Winter Burn” available at

Hot-Water Seed Treatment for Disease Management

Extension Logo

UW Plant Disease Facts


Authors:   Sean Toporek and Brian Hudelson, UW-Madison Plant Pathology
Last Revised:   03/01/2024
D-number:   D0064

Growing vegetables from seed is a common practice for many home gardeners.  Unfortunately, vegetable seed (even though it appears perfectly healthy) can sometimes be contaminated with disease-causing organisms, particularly disease-causing bacteria.  Bacterial speck (see UW Plant Disease Facts D0011, Bacterial Speck of Tomato), bacterial spot (see UW Plant Disease Facts D0012, Bacterial Spot of Tomato), and stem canker of tomato, as well as bacterial spot of pepper and black rot of crucifers such as cabbage and broccoli (see UW Plant Disease Facts D0019, Black Rot of Crucifers) are common bacterial diseases where pathogens can be introduced into a garden via contaminated seed.  Making sure your vegetable seed is pathogen free is an important first step in preventing these diseases from being a problem.

Hot-water treatments can eliminate disease-causing organisms from seed.
Hot-water treatments can eliminate disease-causing organisms from seed.

Hot-water seed treatment is one method that you can use to eradicate, or at least reduce the level of pathogens (particularly bacterial pathogens), in vegetable seed.  Some commercial vegetable seed companies routinely use this method (as well as other more stringent decontamination methods) to eradicate pathogens.  Hot-water seed treatments are effective because hot water soaks into the seed for a brief time and kills disease-causing organisms, without killing the seed itself.  Other common seed treatments (e.g., fungicide treatments) can also help reduce disease, but typically do not eliminate pathogens that have penetrated the seed coat.

Hot-water seed treatment works best for small seed.  It is not as effective for large or extremely fragile seed, pelleted seed, primed seed (i.e., seed treated to speed germination), fungicide-treated seed, and old seed.  When using hot-water seed treatments, treat only the amount of seed that you plan on planting.  Treatment temperatures and durations will vary depending on the particular crop (see Table 1).

To most effectively hot-water treat seed, use a water bath (in home cooking often referred to as a “water oven”) with precise temperature and timing control.  Such equipment will provide the most consistent and uniform heating, but unfortunately can be somewhat expensive.  Alternatively (but much more of a challenge), you can try to use a large pan heated on a stove.  In order for this method to work, you will need to use a precise thermometer to accurately and frequently measure any changes in temperature.  In addition, you must mix the water thoroughly, adjust the stove settings appropriately and submerge the seed completely during the treatment process to ensure that the seed receive a constant and uniform temperature at all times.  Water that is too hot may injure the seed; water that is too cold will not eradicate pathogens.

To hot-water treat seed, use the following steps:

  •  Wrap seed in a permeable cloth (e.g., cheesecloth);
  • Thoroughly soak (removing any air) and pre-warm seed in 100°F tap water for ten minutes;
  • Transfer seed to tap water heated to the crop-specific prescribed temperature (see Table 1);
  • Place seed in cold tap water for five minutes to quickly end the heat treatment;
  • Spread seed out on a paper towel or screen to air dry;
  • Apply fungicide seed treatments according to the manufacturer’s instructions (optional).

Table 1.  Hot-water treatment temperatures and timings by crop*

Crop Temperature (°F) Time (minutes)
Brussel Sprouts 122 25
Broccoli 122 20
Cabbage 122 25
Carrot 122 20
Cauliflower 122 20
Celeriac 118 30
Celery 118 30
Chinese Cabbage 122 20
Collards 122 20
Coriander 127 30
Cress 122 15
Cucumber 122 20
Eggplant 122 25
Kale 122 20
Kohlrabi 122 20
Lettuce 118 30
Mint 112 10
Mustard 122 15
New Zealand Spinach 120 60-120
Parsley 122 30
Pepper 125 30
Radish 122 15
Rutabaga 122 20
Shallot 115 60
Spinach 122 25
Tomato 122 25
Turnip 122 20

*Table modified from

For more information on hot-water seed treatment: 

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or

This Fact Sheet is also available in PDF format:

© 2017-2024 the Board of Regents of the University of Wisconsin System doing business as University of Wisconsin-Madison Division of Extension.

An EEO/Affirmative Action employer, University of Wisconsin-Madison Division of Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. This document can be provided in an alternative format by calling Brian Hudelson at (608) 262-2863 (711 for Wisconsin Relay).

References to pesticide products in this publication are for your convenience and are not an endorsement or criticism of one product over similar products. You are responsible for using pesticides according to the manufacturer’s current label directions. Follow directions exactly to protect the environment and people from pesticide exposure. Failure to do so violates the law.

Thanks to Diana Alfuth, Amanda Gevens and Christy Marsden for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website:

Submit additional lawn, landscape, and gardening questions at


March: Seed Starting and Damping-Off

Preparing for Spring

March is the month when many gardeners begin to think about starting vegetables and ornamental annuals from seed indoors.  While seed-starting can be an economical method for producing plants for home gardening, damping-off can put a damper (no pun intended) on this fun winter gardening activity.

Forms of Damping-Off

Damping-off can take on many forms:

  • rot of seeds prior to germination,
  • rot of seedlings before they reach the soil surface,
  • collapse of seedling stems after emergence followed by plants toppling onto the soil surface (the most classic form of the disease).

Gardeners often blame damping-off on poor seed quality, but disease-causing fungi (and other similar organisms) are the real cause of the problem.  Luckily, only seeds and young plants are susceptible to damping off; older plants are immune to the disease.

Lower stem collapse of Zinnia seedlings due to damping-off.
Lower stem collapse of Zinnia seedlings due to damping-off.

Prevention of Damping-Off

Use new or decontaminated growing containers, working surfaces and tools.

Damping-off pathogens can survive on inert surfaces.  Rinse items like pots and potting stakes thoroughly to remove soil and then soak them for 20 to 30 minutes in 10% bleach.  Rinse items well after treatment to remove bleach residues.  This treatment works well to decontaminate clay and ceramic containers, but is less reliable for plastic items.  If you have had damping-off problems in the past, discard plastic containers and labels and start with new items.  Also use 10% bleach to decontaminate surfaces where you work with seeds and plants.  For metal tools, use a 30 second dip in 70% alcohol (e.g., rubbing alcohol) to decontaminate or alternatively use a spray disinfectant (spray until tools drip and then allow them to air dry).

Use pasteurized soil to start seeds.

Pasteurized soils are steam treated which helps kill disease-causing organisms.  Never use garden soils as these typically contain low levels of damping-off organisms.

Use high quality, vigorous seed.

High quality seed germinates rapidly and resulting plants quickly mature and become immune to damping off.

Plant seeds at the proper depth.

Check seed packets for information on proper panting depth.  When seeds are planted too deeply, plants mature less quickly and remain susceptible to damping-off for a longer period of time.

Germinate seeds at high temperatures.

High temperatures stimulate rapid germination and growth, resulting in a shorter period of time when plants can become infected.  Check out heated seed germination mats, which promote rapid plant growth.  They can help prevent damping-off.

Do not overwater.

Damping-off pathogens are more active in wet soils.  Keep soils drier to reduce pathogen activity and limit infections.

For More Information

See the University of Wisconsin Garden Facts “Damping-Off” available at

February: the PDDC Brings Education to You

Did you know that the PDDC offers educational programs throughout the state of Wisconsin?

Take a look at our stats from last year:

2017 PDDC Educational Statistics

This year is shaping up to be even busier.

Talks and Workshops

Brian Hudelson, the PDDC Director, designs and delivers custom, in-person presentations to groups throughout the state of Wisconsin.  Target audiences include home gardeners, professionals in the green industry (e.g., arborists and greenhouse producers), and Master Garden Volunteers.

Talks and Workshops


Brian’s presentations can cover virtually any topic related to plant diseases including, but not limited to, diseases of fruits and vegetables, diseases of trees and shrubs, and diseases of herbaceous ornamentals.


You can find Brian’s 2018 presentation schedule here:
2018 Outreach Events Calendar

Check the calendar for the topics, locations, and what educational materials he will provide for each presentation.

How to Book a Talk

If you’d like Brian to give a presentation to your group, contact the PDDC at

Be aware that Brian’s schedule fills quickly and he is currently booking presentations well into 2018.

Informational Booths

Want to speak with PDDC staff in person, one-on-one?

The PDDC provides informational booths at select events during the year.  Brian, other clinic staff and graduate students from the UW-Madison Department of Plant Pathology can answer your questions on plant diseases and how to manage them.

Informational Booths

The PDDC’s next informational booth will be at Garden Expo February 9-11 at the Alliant Energy Center in Madison, WI.  Garden Expo is one of the largest garden shows in the Midwest and serves as fundraiser for Wisconsin Public Television.

Radio and Television

Brian Hudelson (aka Dr. Death) is a regular guest on Garden Talk with Larry Meiller on Wisconsin Public Radio (WPR), and has appeared regularly on The Wisconsin Gardener on Wisconsin Public Television (WPT).

Radio and Television

Past Appearances


listen to Brian’s past appearances on Garden Talk on the WPR website.


watch Brian’s past appearances on The Wisconsin Gardener on WPT website.

Need More Information?

To learn more about PDDC outreach activities, check out the PDDC Clinic Services and Clinic Outreach brochure.

To book Brian for a talk or event, contact the PDDC at

January: Pruning in the New Year

January is the time of year to start thinking about maintenance pruning for the trees and shrubs in your yard.

While there are exceptions, for many trees and shrubs, pruning during colder weather (when disease-causing organisms and insects are not active) can help minimize infections through pruning wounds.

The “January Thaw”

If you decide to prune, watch for the “January thaw,” when temperatures are warm enough that you will not freeze to death outside, but cold enough for plant pathogens and insects to have limited activity.

How To’s

For details on pruning, see:

Preventing Infections

As an added precaution to prevent infections, consider routine disinfestation (i.e., decontamination) of pruning tools as you prune.  In the best of all possible worlds, you should decontaminate between every pruning cut.  However, due to time constraints, this may not be feasible, but do consider disinfesting tools between every tree or shrub.

Dip them in alcohol

The best and probably easiest way to disinfest pruning tools is to dip them for at least 30 seconds in 70% alcohol (e.g., rubbing alcohol).

Use spray disinfectants

You can also use spray disinfectants that contain roughly 70% alcohol, in which case you spray your pruning tools until they drip and then allow them to air dry.

Dip them in a bleach solution

As an alternative to alcohol, you can dip tools for at least 30 seconds in a 10% bleach solution.


Bleach is corrosive to metal tools and will induce rusting when used repeatedly.

For More Information

For addition details on proper pruning, contact your county UW-Extension office or contact the PDDC at