Fall officially arrived on September 23rd. Many places in North America have already experienced cold temperatures, and even snow! Yet, some areas are still enjoying warmer weather. If you haven’t yet experienced temperatures cold enough to bring on frost, consider yourself lucky – you still have time to prepare for sinking temperatures and garden-damaging frosty conditions.
What exactly is frost, and what causes it?
There is a simple, scientific answer for this question. In the daytime, your garden plants and their surrounding soil are constantly absorbing and storing heat from the sun.
As we progress into the evening and night hours, your plants quickly lose all of their stored heat.
When we have cloudy skies, the clouds help to insulate and slow down your plant’s heat loss. But, on nights that are cloud-free (and, especially nights that are also wind-free) your plants will lose their heat even faster. The soil temperature and the temperature of the plant cells can possibly even dip a few degrees lower than the air temperature.
When temperatures drop, any moisture in the air will condense and become dew, which your plants will become lightly coated with. If the temperature drops to freezing levels, the dew on your plants will turn to frost, and can damage your plants.
Are all plants prone to frost-damage?
All plants are classified by the minimum temperatures they can tolerate. Plants that are considered “hardy” can typically tolerate a bit of short-term freezing. However, plants that are considered “tender” are typically damaged or killed off by any freezing temperatures. Be sure to know how each of your plants are classified, and prepare your garden for freezing temperatures and frost.
What measures can I take to protect my garden from frost?
There are a few measures you can take to protect your garden plants from freezing temperatures and frost:
- Water your soil thoroughly during the day, when the temperatures are higher. Watered soil will always hold heat better than dry soil. Doing so will protect the roots of your plants, and keep the air temperature higher around your plants.
- Use a bed sheet, plastic sheets, or plastic drop cloth to cover your plants before dusk. Make sure you use some sort of plastic or wooden stake to keep the covering from touching your plants. Be sure to remove the coverings during the warmer daylight hours.
- For small individual plants, you can cover them with milk jugs (with the bottoms cut out), Mason jars, or upside down flower pots.
- Move container plants to a sheltered location; or indoors if you have the space for it. Keeping them close together will help retain heat around the plants more effectively.
- Container plants can also be wrapped in a heavy towel, blanket, burlap material, or bubble wrap to help insulate the container, and protect the roots of your plant.
- Stop fertilizing your plants in early September. This should prevent your plants from growing any new foliage. If there is new foliage on your plants, they are more likely to be damaged by cold temperatures. Older foliage is tougher and stands a better chance against frost damage.
- Even slight wind will prevent freezing air from settling at ground level during the night hours. Create an artificial breeze with an electric fan. Of course, be sure to protect your fan from water and outdoor elements.
What if my plants still end up damaged by frost?
Even if you work hard to protect your plants, they may still end up damaged by cold and frost. If they become damaged, leave the affected areas alone. Pruning off the affected areas can leave the plant even more susceptible to cold and frost.
Wait until the warmer spring weather returns in March and April to see if your plant grows new leaves. When you see new growth around the base of your plant, you will be able to prune away any of the dead, damaged areas. If the plant does not show any signs of new growth, then remove the plant and replace it with something that is more cold-tolerant.