Lettuce contains significant water, and therefore it can easily become a slimy mess if it freezes and thaws. However, standard iceberg lettuce has some flexibility in its tissue, and can withstand a bit of frost without dying. Lettuce varieties such as romaine and leaf lettuce are even more tolerant of frost, but still require some protection. Adding extra mulch layers, covering your lettuce plants with blankets, and watering your lettuce in the afternoon if a drop in temperature is expected are all great ways to protect your plants from frost.
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Three Ways to Protect Lettuce from Frost
Lettuce is one of the world’s most popular garden vegetables, but like all plants, you do need to protect it from harsh temperatures. Although it is a somewhat cold-tolerant vegetable, frost can damage it beyond repair. Below are three simple and easy ways to protect your lettuce from frost:
Invest in Frost Blankets or Cloches
A time-tested way to protect your lettuce plants from frost is to invest in frost blankets or cloches to cover your plants if an early frost occurs or at anytime temperatures are expected to dip. Emergency thermal blankets make great covers as well. It just depends on your personal preferences.
- Invest in these frost blankets, thermal blankets, or cloches to protect your lettuce from frost.
- Do not allow coverings to touch the plants, as this may allow fungus-based diseases to attack.
- Never wait until the last minute to put your coverings in place.
It’s important to make sure the blankets don’t touch the actual plants because lettuce is highly susceptible to fungus-based plant diseases. Therefore, creating a dark, moist space gives these opportunistic diseases the perfect chance to attack. When using frost blankets or cloches, be careful to put them in place well before the frost is expected to occur. Trying to do it at the last minute or waiting until a frost is underway is not recommended, and may even make things worse.
Water Your Lettuce in the Afternoon
Although it may sound counterproductive, water your lettuce in the afternoon when frost season is looming. This is because moist soil has an insulating effect on plants. Moisture helps the soil to retain daytime heat and resist frost.
- When a frost is expected, water your lettuce in the afternoon.
- Wet soil actually resists freezing better than dry soil.
- Always water from the plant’s base.
The heat that the moisture creates radiates upward, thus counteracting Jack Frost when he makes his appearance. The best time to give your lettuce extra water in the anticipation of an overnight frost is midday, when temperatures are warmest. Always water at the base to ensure all the water seeps into the soil.
Add a Layer of Mulch
Adding a layer of mulch to your lettuce beds is one of the easiest measures to take when a frost is on the way. This is because mulch creates a barrier against the cold, and can protect the roots of the plant. This is important, because in your efforts to protect the portion of your lettuce that is above the ground, you may overlook the fact that the roots can also be damaged by frigid temperatures.
- Place 3–6 (7.5–15 cm) inches of mulch around your lettuce plants if frost is expected.
- Add your mulch during the heat of the day so it will absorb some warmth before nightfall.
To create the best barrier, mulch heavily, to a depth of 3 to 6 inches (7.5–15 cm). Avoid using any kind of mulch that contains clay or stones. Instead, opt for wood chips or shredded bark mulch. Even mulched leaves can be used. These kinds of mulch mixtures offer the best warmth, which is obviously your goal. Create your desired mulch beds early in the day when frost is predicted. That way, if the sun shines that day, it will warm the mulch and give it a little “boost” as evening sets in.
Does Frost Hurt Lettuce?
Frost can definitely hurt lettuce. Frost damage takes place when the liquid in the tissues of the vegetable freezes and bursts because of temperature drops. Once this occurs, your plants may not survive.
- Frost can be very harmful to lettuce.
- Lettuce typically won’t survive when temperatures dip under 25℉ (-4℃)
If the frost just barely reaches 32℉ (0℃), your lettuce may make it. If the thermometer reads 25℉ (-4℃) or lower, however, your plants are unlikely to survive, especially if they spend more than four hours in freezing conditions without any protection.
When Should You Protect Lettuce from Frost?
Start protecting your lettuce from frost whenever temperatures are expected to drop to 32℉ (0℃) or lower. Butterhead, romaine, and leaf lettuce typically make it through a 30–32℉ (0 – -1℃) degree frost unharmed, while red leaf and iceberg lettuce may be damaged at that temperature.
- Always protect your lettuce from frost when temperatures dip below 32℉ (0℃).
- Some lettuce is more frost-tolerant than others, but most will die in frigid temperatures.
Nevertheless, even though certain types of lettuce may easily withstand one or two frosts at 32℉ (0℃)t or lower, it’s still better to err on the side of caution. Just to be safe, protect all types of lettuce from frost whenever possible.
How to Cover Lettuce from Frost
You can use several methods to cover lettuce from frost. Although some varieties can make it through a light frost, many will die if subjected to frigid temperatures.
- Lettuce has high water content, so it is susceptible to frost damage.
- Romaine and butterhead lettuce are the most frost-resistant varieties.
- Use frost blankets or cloches to protect your lettuce plants from frost.
- Watering your lettuce in the afternoon when frost is coming helps to keep the ground warm.
- Adding extra layers of mulch to your lettuce beds can create a barrier of protection against frost.
By blanketing your lettuce with a row cover, mulching the ground, and keeping the soil moist you can protect your lettuce from cold temperatures. Just remove your row cover once temperatures rise above freezing so your lettuce can get some sun.