Protecting Garden and Landscape Plants During Cold Weather
Arctic air is on the way – scheduled to arrive in full force tonight with low’s dipping into the upper teen’s and even colder temperatures expected for Tuesday night. Temperatures are not expected to fall below the average minimum for our hardiness zone (Zone 8a, 10-15 degrees) so landscape plants rated hardy to zone 8a or lower should not be seriously damaged. Temperatures this cold will likely damage cold sensitive plants such as sago palm, oleander, sandankwa viburnum and shrubs rated as hardy to zone 8b and above. These plants should be protected to minimize cold weather damage.
Vegetable gardens are at greater risk than landscape plants. Temperatures in the teens will likely damage vegetable crops – even relatively hardy crops like cabbage, kale and collards could be damaged. More tender cool season crops such as lettuce, beets, Chinese cabbage, and chard could be killed if unprotected. Moderate winds will compound damage to unprotected crops by increasing dessication of plant leaves.
Here are some tips for helping your cold sensitive landscape plants and cool season vegetables survive winter cold snaps:
- If soils are dry, water the garden or landscape well at least a day before extreme cold sets in. Moist soil holds heat longer and is more insulating than dry soil. Due to recent rains, soil moisture levels should be good during this cold blast. Do not over water in winter – wet soils increase root and crown rot diseases.
Cover cold sensitive plants when night time lows are expected to dip below 20 degrees F. Cover vegetable crops when temperatures are predicted to fall below the mid 20s. For this upcoming cold snap, I would wrap plants like sago palm in a blanket and cover vegetables with floating row cover Monday evening and not worry about uncovering them until Wednesday or Thursday morning. Plants will be fine covered for a couple of days through extreme cold weather.
- If you do not have any floating row cover or frost protection fabric, cover plants with old blankets or other insulating materials. Double layers provide more protection than single layers. Make sure covers extend down to the ground and are securely held down by bricks or staples. Most of the protection provided by covers is from the soil warmth they trap in, which would otherwise radiate out into the night.
- Lay row cover fabrics, blankets, or double layers of plastic directly over crops or build a low frame or hoops out of PVC or other materials to create a mini greenhouse over crops. Uncover crops as soon as milder temperature return.
- Smaller plants can be covered with a thick layer of dry leaves or pine straw. For larger shrubs such as figs, you can build a wire cage around individual plants or beds to help hold leaves in place and cover with an old sheet. Cover plants completely so no green is exposed for best protection.
- Plants growing in containers are more sensitive to cold than plants growing in the ground. Move containers to protected locations such as against the house under the eaves, onto a porch, in a garage, or under dense trees. If containers cannot be moved, wrap the entire container in thick layers of insulating materials such as bubble wrap or old blankets, or build a wire cage around them and fill with straw.
Open blossoms and blossom buds showing color are more sensitive to cold than other plant parts. If you have camellias, blueberries or other early blooming shrubs with open blossoms and wish to protect the blossoms, completely cover the bushes with row cover or blankets. Make sure covers extend all the way down to the ground and they are staked down. Blueberries do not open all their blossoms at one time so even if you lose some blooms now, your crop will not be lost.
- Strawberry plants should be covered even if blossoms are not present.
Many garden centers and online suppliers sell floating row cover such as Remay – here is one example: http://www.gardeners.com/Row-Covers/5111,default,pg.html
Cold frames are an alternative to floating row cover. Find out more about building and using cold frames from this Missouri Extension fact sheet: http://extension.missouri.edu/publications/DisplayPub.aspx?P=G6965
Find the latest forecast for your area from the National Weather Service:
Not sure of your landscape plants’ hardiness? Find out the USDA hardiness rating and much more from the N.C. Cooperative Extension Plants Database: http://plants.ces.ncsu.edu/
Learn more about the USDA Plant Hardiness Zone Map and look up zone ratings for anywhere in the US: http://planthardiness.ars.usda.gov/PHZMWeb/#
Extension Fact Sheets on Protecting Landscape Plants from Cold:
- Florida: http://extension.ifas.ufl.edu/hot_topics/lawn_and_garden/cold_protection_of_ornamental_plants.html
Use Extension Search to find research based information from Cooperative Extension systems across the U.S.
Visit your local Cooperative Extension office to learn more about gardening and landscape care. Go to https://www.ces.ncsu.edu/local-county-center/ to find your county Extension center or post your questions to be answered online via Extension’s ‘Ask an Expert’ widget.
Contact your local Cooperative Extension office to get expert advice from an Extension Master Gardener Volunteer:
- If you live in Pender County, call 910-259-1235
- In New Hanover County, call 910-798-7660
- In Brunswick County, call 910-253-2610
- In Onslow County, call 910-455-5873
- In Duplin County, call 910-296-2143
Visit the Pender Extension Lawn and Garden webpage to stay up to date with all the latest gardening news.