Extension Master GardenerSM Volunteers of Buncombe County

freeze

Have You Heard of Blackberry Winter?

The term “blackberry winter” might make you think of enjoying blackberry cobbler on a cold winter’s day. What it really refers to is a cold spell that happens in the spring when blackberries are flowering. And this weekend in Western North Carolina, as the blackberries come into full bloom and forecasted temperatures drop into the low 30’s, we will experience a “blackberry winter.”  Many of our plants will be affected by the cold temperatures and frost, not just blackberries.

Mitigating factors
Damage to plants can vary and will depend on several factors.

  • Cloud cover and light winds can moderate temperatures and reduce the chance of frost settling on plants.
  • Developmental stage of the plant is also key. Plants sprouting tender new growth of foliage, flower, and fruit are highly susceptible to damage. Plants fresh from the greenhouse and not acclimated to the outdoors may also be hurt.
  • Garden location affects the level of damage or protection a plant receives. The climate of a garden site, often called a microclimate, is affected by the lay of the land, nearby structures, and windbreaks. Cold air and frost pockets settle near the bottom of a slope. Structures and windbreaks can provide warmth and protection.

Plant susceptibility
Cold temperatures and frost will impact plants in the following ways:

  • Fruit trees vary in their hardiness according to their stage of flowering. If fruit trees have flowered and set their fruit, they should be safe from a light frost. Lower temperatures that damage some fruit is simply an act of nature that thins the fruit, giving the remaining fruit space to grow to full size.
  • Small fruits that are in flower, like blueberries, strawberries, blackberries, and raspberries, will be susceptible to damage and ultimately may not set fruit.
  • Warm season vegetables, such as peppers, tomatoes, and cucumbers, and all tender annual flowers will be damaged if temperatures drop into the low 30’s.
  • Cool season vegetables, such as early peas, greens, beets, carrots, onions, broccoli, and cabbage, are all considered cold hardy and can withstand freezing temperatures with no notable damage.
  • New growth on ornamental trees and shrubs, such as Japanese maples (already hit once this season), hydrangeas, and roses, can be damaged. As will the flowers of azaleas and rhododendrons that are right now in their full glory. Flowers still in tight bud should be okay.

Protection
If possible, cover your plants as the temperature drops.

  • Lightweight fabrics, such as floating row covers, frost blankets, or other polyspun materials, work well for frost protection. If you do not have this type of fabric, cotton sheeting, lightweight blankets, or other insulating materials can be used. Double layers provide more protection than single layers. Make sure covers extend down to the ground and are anchored by bricks, stones, or landscape staples. This protects the plant from blowing wind and secures openings where heat can escape.
  • Plastic coverings or tarps can work, but because of weight should be used with caution on more delicate plants. Keep plant foliage from coming in direct contact with the plastic since this can cause the leaves to freeze.
  • Buckets, containers, or other devices are an easy way to cover individual vegetable plants and provide frost protection as long as the plant can be adequately covered without damage.

Always, always, always be sure to uncover plants as soon as the temperature begins to rise the next day. This is especially important when using clear plastic. The chance of plants overheating and burning from bright sun and warming temperatures creates another problem entirely.

It is helpful to point out that the Buncombe County Extension Master GardenerSM  recommendation is to delay planting warm season vegetables and flowering annuals until Mother’s Day . . . which is this coming weekend!

The blackberry winter experience
Given our “stay home stay safe” time this year, many gardens are well on their way to full growth and beauty.  Although it is worth making the effort to protect plants from freezing temperatures, protecting all your plants may not be possible.  Do the best you can. Blackberry winters will always come and go. Some plants will die, some will be damaged, and many will survive. This is part of every gardener’s experience here in Western North Carolina. Be resilient, plant again, and take pleasure in the learning.

Article written by Alison Arnold, Buncombe County Extension Consumer Horticulture Agent/Master Gardener Volunteer Program

More information:  Managing Frost in the Garden 

What NOT to Do in the Garden

Frost has left your yard looking kind of dead. You hear the neighbors blowing leaves and see them busily tidying up—you feel guilty that you’re going out for a hike or sitting inside dreaming of next spring rather than doing yardwork. But you may be doing your landscape a favor by doing less!

Leaves that need to be raked, bagged or not ?

What to do with leaves?
Do you really need to rake up and dispose of leaves?
Leave them! In many cases, you can simply leave them where they fall: in wooded areas, under trees or shrubs, on your vegetable garden, flower beds—in fact, almost anywhere but a lawn, leaves can act as a mulch and eventual soil enrichment.
• Move them where needed. If the leaves are constantly blowing back onto your lawn, or are matting and smothering groundcovers or small plants, move them to other areas where they can break down in peace.
• Shred them with a shredder or lawn mower. Shredding will help leaves stay in place and break down more quickly. Using a mulching mower on your lawn before leaves get too deep will save you from raking there, too.
• The bottom line: If you must rake, save your leaves in a compost pile or in an unobtrusive area of your yard to spread back on your planting beds once they break down.

What about leaf blowers?
If you must move leaves around, consider that these concerns—Electric or gas blowers may:
• Harm beneficial insects, small animals and their habitats
• Damage plants and shrubs
• Create noise and air pollution.

What about pruning?
With the exception of diseased or damaged wood, leave pruning shrubs and trees until late winter—or immediately after bloom in the case of trees and shrubs that bloom on “old” wood.

Evening primrose_Oenothera biennis_seed pods_Andreas Rockstein_CC BY-SA 2.0_Flickr
Consider leaving seed heads for awhile.

What about annual and perennial plants?
Although you may be tempted to cut everything back in the interest of neatness, consider leaving dried seed heads for winter interest, self-sowing, and feeding the birds—at least until the seeds are gone or stems start to break down. One exception, of course, is if plants seed so aggressively that they become nuisances. Consider removing such plants and replacing them with more desirable alternatives.

Enjoy your break from yardwork!
Take time to reflect on what is working well in your garden and what needs rethinking. How does your yard look at this time of year? Does it have good “bones” that make it attractive in all four seasons, or do you need to consider adding some new plants that look good in fall or winter? Do you need to remove failing or overgrown trees or shrubs? Is there too much lawn? You still have time to plant this fall—until the ground is frozen—or start planning for next year!

Take time to evaluate your landscape.

Article by Debbie Green, Extension Master GardenerSM Volunteer

For more information about fall planting:

https://chatham.ces.ncsu.edu/2017/09/fall-is-the-best-time-to-plant-trees-and-shrubs/

 

Abiotic Plant Disorders: You be the Detective!

We usually think of plant problems as due to pests or diseases: Biotic agents! These living organisms include insects, disease causing pathogens, nematodes, parasitic plants, and viruses. But abiotic—nonliving agents—can also injure our landscape plants. If you think about it, you’ve probably lost plants to many of these, which include environmental extremes in moisture and/or temperature; mechanical damage, such as severe root cutting; and chemical factors, such as high soil salinity or herbicide damage.
Accurate diagnosis is key to remedying any plant problem, biotic, abiotic, or both!

How to diagnosis?
• Identify the plants: Determine the botanical name: genus, species and family—plant labels usually have plant genus and species and with that information you can look up the plant family.
• Identify the symptoms: Chlorotic (yellowing), necrotic (blackening or death), or distorted plant parts. Be thorough and accurate!
• Inspect the whole plant: Examine all parts of the plant, not just the injured area.
• Look for patterns: Are symptoms uniform throughout the plant or scattered?
• Inspect the site: Is the soil well-drained, is there recent evidence of disturbance, how long has the plant been in the ground?
• Do you have any records of plant care—watering, fertilizing, pruning, spraying?
• Identify likely causes from the information collected— Keep in mind that there may be multiple causes!
• Collect samples and submit for testing to rule out disease or insect problems at the North Carolina Plant Disease and Insect Clinic.

Examples and symptoms of common environmental abiotic plant problems:

Water—Too much or too little—both can damage plants! Waterlogging kills roots if oxygen levels in the root zone are too low, but excess soil moisture is more commonly a factor in root disease. At the other extreme, insufficient moisture can result in scorch symptoms on foliage, stunting, leaf yellowing, leaf drop, early Fall color; and death of flowers and fruits.

Flooding
Drought Damage to Trees

 

 

 

 

 

 

Sunscald usually occurs in late winter or early spring when sunlight heats tree bark during the day. This causes the water in the ground to start to rise from the roots. With freezing nighttime temperatures, this water freezes within the bark tissue and an elongated canker can form that appears discolored and sunken. Cracking and peeling bark may follow. It may be the next spring or summer when new growth occurs before the damage shows. Tree with thin bark such as beech (Fagus), dogwood (Cornus), honey locust (Gleditsia triacanthos), linden (Tilia), mountain ash (Sorbus americana) and sugar maple (Acer saccharum), and newly planted trees are especially susceptible.

Frost Crack …. University of Michigan

Wind moving across leaves takes moisture from them, sometimes in excessive amounts resulting in a scorched appearance. Evergreen trees and shrubs are particularly susceptible to this during the winter when the roots cannot extract water from frozen soil.

Wind

Low temperature—Plants have critical temperature levels at or below which they may experience frost or freezing injury. Plant cells are injured when the temperature falls below a critical level for a species. Injury at above freezing temperatures is called chilling injury. Such injury may affect any plant parts of both evergreen and deciduous plants. Young leaves are most sensitive to lower temperatures; injured leaves look water soaked and black. Flowering plants putting on new growth are especially susceptible. It may be a few weeks before you see damage from cold temperatures. To minimize injury from low temperatures be sure to select plants that are hardy in your area—Zones 5b to 7a, depending where you live in Buncombe county.

Freezing Temperatures

Article by Bob Wardwell, Extension Master GardenerSM Volunteer

Abiotic Disorders of Plants  https://content.ces.ncsu.edu/extension-gardener-handbook/5-diseases-and-disorders#section_heading_7612

Sunscald of Woody Plants www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/environmental/sunscald/sunscald-of-woody-plants.aspx

Abiotic Disorders of Landscape Plants: A Diagnostic Guide, Costello, L., et al., University of California Press, February 2014.

How to submit a sample for Insect and disease identification: https://projects.ncsu.edu/cals/plantpath/extension/clinic/submit-sample.html

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Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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