Extension Master GardenerSM Volunteers of Buncombe County

freeze

Warm Season Vegetables: Just Because They Are for Sale Does NOT Mean it is Time to Plant Them!

In late April, walking through the garden section of many stores you’ll see tomato, pepper, squash, and cucumber plants for sale. Does this mean it is safe to plant them now?

Freeze Dates: Data on last spring freeze dates in Western North Carolina are critical to the survival of the warm season plants. In this region of the state, tomatoes, peppers—and often cucumbers and squash—are grown from transplants, not direct seeding.  Immediately after planting, they are exposed to the see-sawing air temperature fluctuations that occur during this time of year.

Frosted Leaves

The dates after which there is only a 10 percent chance of a spring freeze (32° F) based on data collected by National Oceanic and Atmospheric Administration (NOAA) from 1981-2010 for selected locations in Buncombe County Western North Carolina are:

Downtown Asheville          April 27

Asheville Airport                 May 4

Fletcher                               May 7

Black Mountain                  May 11

Swannanoa                        May 12

Bent Creek                         May 13

To be safe, then, Buncombe County Extension Master GardenersSM recommend not planting these crops in the ground until Mother’s Day each year. For your specific location and the weather forecast for any particular year, you may choose to plant earlier or later!

If you do choose to transplant earlier, be prepared to provide some type of frost protection when the temperature is expected to go below 36° F.  Techniques for frost protection include covering growing beds or rows with a floating row cover (supported by stakes or wire to keep the material from directly touching the plants). Protect individual plants with plastic milk jugs with the bottoms removed, paper caps, or water-holding walls.

Floating row cover tunnel_Carol Jacobs-Carre_CC BY-NC-ND 2.0_Flickr
Floating row cover

We also recommend “hardening-off” to toughen up your plants before putting them into the ground. Gently stroking your plants a few seconds every day while they are still indoors is helpful. Starting about seven days before you intend to plant, on warm days place your transplants—while still in their growing containers—in the general vicinity of the garden in a protected area to expose them to your intended growing conditions. This is especially important for any plants grown under greenhouse conditions.  You will need to make sure they have adequate water and bring them indoors at night to ensure their survival.

Article by Bob Wardwell, Extension Master GardenerSM Volunteer

Learn more:

Hardening off

https://polk.ces.ncsu.edu/2019/03/simple-but-necessary-hardening-off-vegetable-seedlings/

Western North Carolina Planting Calendar for annual vegetables

https://extensiongardener.ces.ncsu.edu/wp-content/uploads/2016/07/NC-Vegetable-Planting-Guide-1.pdf?fwd=no

US Normals Data (1981-2010) for Buncombe County Weather Stations:

https://www.ncei.noaa.gov/orders/cdo/1712624.pdf

Protecting Your Woody Plants from Winter’s Wrath

In October, the NOAA (National Oceanic and Atmospheric Administration) forecast a warmer than normal winter for our area. That’s not good news for us gardeners, or for our woody plants! 

Why warmer weather isn’t better
Our shrubs and trees struggled all summer—and now into the fall—with higher-than-normal temperatures and lower-than-normal moisture. Once cooler weather arrives, even short increases in temperature can cause buds to break dormancy. And lower-than-normal cold snaps that accompany our increasingly irregular weather make things worse.

Which woody plants are most vulnerable?
Plants aren’t equally sturdy. Make sure you know what shrubs and trees are in your landscape, as well as their specific requirements. Many popular landscape choices are only marginally cold hardy here in the mountains and your terrain has a lot to do with cold hardiness. Cold air settles in low-lying areas of your yard. Whether a plant is on the north versus south-facing side of your home and has or doesn’t have protection from winds all affect how your plants fare. Evidence is mounting that woody plants with less chlorophyll (green) associated with the foliage—those that are variegated, gold, or purple—are less vigorous than all-green parent species.

Hinoki Cypress_Bark Split from Freeze-Thaw Cycle
Bark split on Hinoki Cypress from freeze-thaw cycle.

What can you do?
To protect your plants from those freeze-thaw cycles—as well as the sunburn, wind, snow, and ice that really do the damage, particularly at higher elevations—you need to provide some additional layers. For plant roots, a good layer of mulch is an appropriate defense. Mulch doesn’t keep the roots warm, but it does protect them from temperature extremes that come with the ground freezing then thawing.

Similarly, protect the upper part of a tender plant by surrounding it with a “blanket.” Drive stakes into the ground around the plant and staple burlap to the stakes. Stuff the spaces between the branches with pine straw. The intent is to keep the plant cold on warm days, rather than warm on cold days. This keeps dormant plants dormant! Avoid using plastic, which traps heat, causing temperatures to rise well above the temperature of the surrounding air.

For evergreens, burlap may help protect from sun- and windburn. Anti-desiccant sprays purport to provide protection, but it may be short-lived. Making sure the roots are well-watered is a better plan to prevent woody plant loss.

Article written by Glenn Palmer, Extension Master Gardener Volunteer.

Your Shrubbery Might Enjoy a Blanket

hardy-gardenia-with-winter-scorch

With all the vagaries of our weather in recent years, my winter forecast is that it will be either warmer than normal or lots colder, leaning toward the latter. In either case, it would be wise to survey your landscape to see where some protection might be a good investment.

The wisest approach is to select hardy Zone 5 plants for your landscape, then place them in a site that will take advantage of the terrain—or perhaps consider buildings for additional protection. South-facing slopes are great because of sun all year long, with cold air drifting downhill. In front of a stone wall is also an option because the wall retains heat.

Cold damage takes different forms and affects foliage, buds, limbs, and trunks in different ways. Often it’s not the lowest temperature that does the damage, but instead, the duration and timing of cold weather.

Boxwood in the snowThe 2007 Easter Freeze came after a prolonged warm spell, long enough to convince some plant species, like Japanese Maples, that spring had already arrived. Even short variations in temperatures can cause buds to break dormancy and lose their hardiness.

For the roots, a good layer of mulch is the appropriate defense. Mulch doesn’t keep the soil warmer but it does slow the freeze-thaw cycles. Once the soil gets cold it stays cold.

You can protect the upper part of a tender plant by surroundings it with a blanket. To do this, drive stakes into the ground around the plant and staple burlap to the stakes as a curtain. Gently stuff the spaces between the branches and the burlap with straw. The intent is to keep the plant cool on warm days, not warm on cool days, which is why burlap is better than plastic. Burlap breathes, keeping the temperature more in line with the ambient, eliminating sudden, short periods of heat. Plastic, whether black or clear, traps the air and allows it to swing above ambient for short periods of time.

Leyland-cypress-with-winter-colorThe same concept can be used to protect evergreen plants against sun or wind burn. Waxy chemical sprays on the leaves can also help prevent desiccation from the wind. This is particularly appropriate for Rhododendrons in windy locations.

To help prevent snow or ice from bending long, pliant branches on a tree or shrub, one can wrap the plant with tape or twine, like a Christmas tree.

Written by Glenn Palmer, originally published in the Asheville Citizen Times.

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

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