Let’s Make a Giant Blanket Fort: Protecting Your Plants from an Early Freeze

Christy’s Garden

Sunday, September 6, 2020

It doesn’t matter how many times we look at our phone, check the local news or refresh the weather channel.  It is going to snow in the Denver metro area on Tuesday.  What sucks about it is that it is only September 8th.  The average first snow is October 15th.  Well, it could be worse.  The earliest date of first snow was September 3 in 1961. [1]  

No.  It still sucks.

Did we mention it is 98 degrees today?  Edith’s tomatoes are just starting to turn red.  Christy’s zinnias are in full bloom.  So much to  harvest and enjoy in the garden.  And in typical Colorado form, it will be in the 60’s by the end of the week with potentially another month of nice weather.  What can a gardener do in this upside down world of weather extremity?  Here is what we can expect to happen to our gardens on Tuesday and what we can do about it.

According to our good friends at the Farmer’s Almanac, dispensing wisdom since 1818,  the fact that it is snowing, as the temps dip into the upper 20’s might actually be in our favor.  If the temperature is cool, but clouds are visible, our plants may be protected. Clouds will trap the heat and keep the warmer temperatures lower, closer to our plants, preventing a frost. When moisture condenses out of humid air, it releases enough heat to sometimes save our plants. [2]

We are preparing for a moderate freeze/killing frost:  25 degrees F to 28 degrees, which can mean wide destruction on most vegetation.  In other words, your begonias and impatiens will most likely die without protection, but your spinach is going to be fine.  We are also expecting 2 – 3 inches of snow, but since it has been so hot, the Denver Channel is reporting most of it should melt on the way down.  

Here is what we are doing: 

  1. Water the soil thoroughly.  It may sound crazy, but watering around plants the night before a frost or freeze can actually protect them from freezing. During the night, the wet soil will release moisture into the air, which will raise the temperature and keep plants warmer.
  2. Make a Blanket Fort:  Bed sheets, drop cloths, blankets and plastic sheets make suitable covers for vulnerable plants. Or floating row cover, a product sold for this purpose. It’s also important to remember that covers don’t have to be elaborate or expensive in order to work. If you can, it’s also advisable to use stakes to keep material, especially plastic, from touching the foliage.
  3. Walls of Water: Employ these small, inexpensive plant protectors that use water as insulation to keep tomatoes or other heat loving plants warm when it’s cold.
Edith’s Garden

4. For smaller plants, inverted flowerpots or buckets work, too.  How about milk jugs with the bottoms removed?

5. Cluster container plants close together and, if possible, in a sheltered spot close to the house.  Or move into the garage.  Maybe they will start a band.

6. Do all this before dusk.  By the time it gets dark much of the stored heat in the garden has already been lost. 

7. It is almost impossible to cover everything.  Plants with big vines, like  Spaghetti squash, butternut, cantaloupe – pick the ones that look like you can ripen them off the vine and leaving as much of the stem as possible.  

8. Harvest! Pull those semi ripe tomatoes. Bring some flowers inside and put them in a vase.

9. Take a breath and be grateful for what we all have harvested and the flowers we enjoyed.

10. Remove the coverings when temperatures rise the next day. Anything that looks OK:  Give it a big kiss. Do a dance in your yard.  Send us pix.

And don’t worry.  If (and WHEN) it all freezes and dies, the garden will forgive you and be ready for you in the spring.  We promise.  

Hard frost hardy:  (less than 28 F)

  • Collards
  • Endive/escarole
  • Kale
  • Kohlrabi
  • Lettuce
  • Mustard
  • Onion (sets and seeds)
  • Pea
  • Potato
  • Rhubarb
  • Rutabaga
  • Spinach
  • Turnip

Light frost hardy (28–32 F)

  • Beet
  • Broccoli
  • Cabbage
  • Carrot
  • Cauliflower
  • Celeriac
  • Celery
  • Chard
  • Onion (plants)
  • Parsnip
  • Radish

Light frost susceptible (28–32 F)

  • Cucumber
  • Edible beans
  • Eggplant
  • Muskmelon
  • Okra
  • Pepper
  • Pumpkin
  • Squash, summer/winter
  • Sweet corn
  • Sweet potato
  • Tomato
  • Watermelon

[1] https://www.weather.gov/bou/snowstat

[2] https://www.farmersalmanac.com/frost-temperature-outdoor-plants-9788