Here is a quick reference on how to handle tonight’s cold temperatures to minimize damage in your garden. While we are not in for a “hard freeze” we will be experiencing some significant frost in the wee hours of Wednesday and Thursday. That means you need to prepare today!
Frost occurs on the surface of plants as the plant loses heat to the surrounding, colder environment. It does not require freezing temperatures (32 degrees) to occur, rather anticipate frost at as warm as 38 degrees! As frost forms on plant surfaces, damage to the leaves occurs. With these “open wounds” the plant is then susceptible to bacterial and fungal disease.
First, make sure all your plants are in the least stressed condition possible. After a couple of days of wind as this front has moved in, they will all require a good soaking. This will also help them out since you probably won’t be watering during the next couple of days when it is so cold.
Then, move whatever you can indoors. A garage or shed is fine, just some protection from the settling cold. Orchids and tropical foliage that may be on your porch are critical.
Then assess what is in your yard that can’t be moved in. Some plants will sail right through this; others are only hardy to Zone 9, 10 or 11. These plants will need protection. If your plant is rated to Zone 8 or less, they should be okay. That means there may be some leaf damage, but the plant will survive.
Coldest temperatures typically occur at dawn or a few minutes after. Frost damage is minimizing with a light breeze of 5 mph or so. This results in a mixing of the air, preventing the colder, denser air from settling down close to the surface of the garden.
Plants that need protection should be covered in some type of fabric. At home we use old sheets I bought at garage sales and thrift shops. There is also a “frost blanket” product available that works nicely. I would caution you to wear long sleeves and gloves when using such products however, since they are often made using fiberglass. Secure your fabric with stones or stakes, or secure it with twine or bungee cords.
Do not use plastic to cover your plants unless you have a cold frame to hold the plastic above the surface of the plants. Plastic will conduct the cold and actually worsen the damage. Plus it tends to flap in the wind, adding insult to injury by physically damaging your plants.
People often ask about using water to prevent cold damage. I typically discourage this approach. The use of water requires impeccable timing, and a commitment to close monitoring of the temperatures.
Water needs to be turned on just before the temperatures hit 34 degrees (usually about 4 am). Once you turn it on, you are committed — you cannot turn it off because the water you applied will start to cool–sucking heat from your plants as it does and worsening the damage. Besides, this type of water use is truly wasteful of our most precious environmental resource.
Below I have a quick list of plants and whether you will need to protect them. Of course it is not all-inclusive, so if you have something cherished you need to know about, Google its botanical name, and look for its hardiness rating. If you don’t know the botanical, Google the common name on the Google “images” tool. Locate the correct plant picture in the thumbnails, and then follow that link to get the name and other information.
I gotta run– we have seven acres to cover!
Good Luck, Stay warm, and oh yeah –Hail to the Chief!