Our mild Texas winters provide a second growing season that is ideal for growing all types of greens and other winter vegetables. Most of the winter, it is not necessary to provide freeze protection for cold hardy vegetables, but there are usually a few days in January and February that will be cold enough that at least some of your winter vegetables will need to be covered/protected.
What is a Freeze?
A freeze happens when temperatures drop to 32 degrees Fahrenheit or lower for a couple of hours or more. Our first freeze usually happens between Halloween and the first week of November. This is the freeze that kills summer vegetables and flowers. It is not usually cold enough to harm our hardier winter greens that were planted in the fall.
Freeze-Kill Temperatures for Winter Vegetables
All of the winter vegetables in this table are cold hardier and grow well during our Texas winters, but if low temperatures are expected to be at or below the cold-hardiness or freeze-kill temperature in this table then that vegetable should be covered for protection. For example, if the low temperature is expected to fall to 25 degrees or lower, lettuce should be covered.
Options for Freeze Protection
1. Greenhouses, hoop houses or cold frames
If you are lucky enough to have a greenhouse, hoop house or cold frame, you can just close the door to protect your plants. While these three options are nice to have, they are not needed by the home gardener since our Texas winters are usually mild. I built a cold frame years ago and most of the winter there is no need to close the door.
There are many more affordable and simple materials that can provide freeze protection including cloches, row cover fabric, and blankets, towels, and bed sheets.
Cloches are bell-shaped glass or plastic coverings for individual plants. Affordable cloches can be created from plastic water and juice bottles. Just cut the bottom off the bottle.
I don’t usually use cloches to protect winter vegetables, but I do use them to provide protection and an early start for young spring seedlings in the garden. Since cloches are like mini-greenhouses, the temperatures can get very warm inside when the sun is shining. So, I don’t put a lid on them unless snow, ice, or temperatures below 20 degrees are expected.
3. Row Cover Fabric
Row cover fabric comes in various thicknesses and is used to cover a row of plants or is placed over a series of small in-line metal or plastic hoops to create a tunnel shape over the plants. Row cover fabric and fabric tunnels are usually left on the plants for some time or moved to the side as the temperatures warm.
4. Blankets, Towels and Sheets
Frost blankets and ordinary blankets provide more protection than thinner bed sheets.
The option I use the most is an ordinary blanket. A thick blanket will provide a good level of protection and is very affordable. If you don’t have an old blanket, one can be purchased for just a couple of dollars or so at a re-use store. The best blankets are thick with a cotton or cotton/polyester cover with batting inside – like a comforter or quilt. A dark color blanket will also absorb more heat from the sun. Fuzzy blankets will keep plants warm, but their surface will entangle small sticks and leaves and will be difficult to keep clean.
How Protect Your Winter Vegetables from Killing Freezes
Watch the Weather Forecast
Keep your eye on the weather forecast and note any days in which the low temperature will be at or below the freeze-kill temperature for your crops. The usual pattern of cold weather development is this: temperatures begin to decline when sun goes down in the evening and continue to drop throughout the night reaching the lowest temperature in the early morning hours of the next day just before sunrise.
What to Do to Provide Freeze Protection: the Steps
Step 1: Water Your Vegetables
Water your vegetables during the warmest hours of the day on the day before the low temperature is expected. This will usually be between 1 pm – 3 pm. Ideally the temperature should be 40 degrees or above when you water. Plants that are watered and have adequate moisture in their cells have a much better tolerance for cold temperatures compared to plants in dry soil. Cold temperatures + dry soil can be a death sentence for your vegetables.
Step 2: Cover Your Vegetables for Extra Warmth
After watering well, cover your vegetables with a blanket, towel, sheet, row cover fabric or cloches. Place rocks, bricks, bulldog clips, clothespins on the corners and edges of fabric covers to keep gusts of cold wind out. If using a cloche and ice and or snow are expected, add the lid.
Step 3: Uncover Your Vegetables Once Temperatures Have Warmed to 33 Degrees and Above
Uncover your vegetables once the temperature has warmed to 33 degrees or above (usually by noon the next day). If you used a blanket, towel or sheet, be sure to let it dry well before folding and storing. If they are heavy with water or slushy snow, put them on a driveway or sidewalk in the sun until they are drier. Then they can be lifted onto a fence or clothesline to dry completely.
If you used row cover, you could leave it, move it to the side, or remove and store it. If you used a cloche, remove, and store it, or just remove the lid so the plant does not get too hot. Winter greens left in cloches for a long period in Texas will usually become too warm, and so produce seed and become inedible. Water your plants again if their soil has been dried out by the cold weather.
Protecting Winter Potted Plants
Potted winter vegetables and flowers can be moved into a greenhouse, garage, or covered with blankets, towels, commercial frost blankets, or frost bags with drawstrings. It is useful to move many potted plants together on a porch or near a wall of the house so you can cover all of them with a single blanket. Tuck the edges of the blankets under the pots to secure them and block drafts of wind.
Extreme Cold Weather Protection
It has been rare, but sometimes we do have extreme cold weather in Texas as experienced in February 2021. This period has been nicknamed by Texans as the Texas Snow Apocalypse. At this time, we received 6” to 8” of snow and had below freezing temperatures that ranged from 16 degrees, to 5 degrees, and even 0 degrees for 7 days in a row. In weather like this, thin fabric such row cover and sheets are probably not going to provide the protection your crops need to survive.
How I Saved My Winter Vegetables During the Texas Snow Apocalypse
First, I watered all my vegetable beds well during the warmest hours of the day before the first freezing temperatures and snow were expected (around 1 p.m.). I then covered each bed with doubled blankets and secured all edges with bulldog clips, clothespins, nails, and rocks. I then pinned a smaller loose sheet of 4 mil. black plastic over the top of each blanket to provide some extra passive solar heat.
On the 7th day of snow cover, I looked under the blanket and saw thriving vegetable greens! By the time temperatures rose above freezing and the snow had melted, it had been nine days total since my plants were first watered and covered. And ALL of my winter vegetables had survived!