Get Your Garden Ready for Frost

We have had a mild summer and fall this year on our farm in Cove, Oregon. The usual Labor Day frost didn’t touch us, but now it is the end of September and frost is inevitable–possibly tonight, September 27. Here are some tips on keeping your garden going a little longer this year.

Frost nipped the top of the pumpkin plants in early September.

Tip 1: Prioritize

Covering your garden every night and uncovering in the morning is tedious, so first prioritize what you really care about and what you can feasibly protect.

By September at latitude 45 north, no flowers will amount to mature vegetables–there just isn’t enough warmth or daylight left. Zucchini is the exception, but you might be tired of zucchini and glad to see it go anyway.

Photo by Pixabay on Pexels.com
Not all your crops need frost protection.

Anything in the Brassica family–kale, broccoli, cauliflower, cabbage–will make it. Lettuce and other leafy greens are also cold tolerant. Root vegetables are protected by stable ground heat. In my family, we dig carrots for Christmas dinner.

Many folks like to leave root crops in the ground and cover with straw for extra insulation. I tried this and even covered the straw with plastic. The mice ate 300 feet of carrots and were happy for their warm, dry home. I prefer to leave them in the ground without creating a mouse house, and have had no trouble with them freezing, especially once the snow falls and insulates them.

Basil can die above freezing–at 35F!
Crops that need protection.

Protect tomatoes, peppers, basil, flowers and any very young seedlings you planted for your fall garden. Remember–basil can die at 35 degrees or lower, so it needs extra protection.

If you bravely planted Dalias, rosemary or other crops that are marginally successful in my zone 5b, you need to come up with a plan to protect them over the winter.

And don’t forget about your potted plants. Above ground their roots will freeze, so bring them inside or dig a hole and put the pot in the ground.

Tip 2: Quicken Ripening

Our most beloved plants didn’t evolve in the northwest. They come from Mexico or Italy–Mediterranean climates. Give your plants more clues that it is time to ripen.

Your indeterminate tomatoes are probably flowering like there’s no tomorrow, but it is time to tell them the end is nigh. Hack off any flowering parts of the tomato. Pinch any flowers from peppers and keep the basil flowers pinched too. Cut way back on water so plants are “shocked” into ripening. Tomatoes need water 0-1 times per week at this point in the season.

If what you’re trying to ripen is flower seeds to save, cut off the water all together.

Photo by Richard Fletcher on Pexels.com

Tip 3: Watch the Weather

Every morning and late afternoon, I check the weather forecast. I want to know the nighttime low and weather the skies will be cloudy or clear. I don’t ready the NOAA forecast or anything fancy. User friendly weather sites for non-weather nerds are fine.

Frost is most likely to form on your garden if the nighttime low is near 32F and the skies are clear. Cloudy skies trap more heat and result in warmer nights. A weather forecast of a low of 35F and cloudy skies doesn’t alarm me as much as a forecast of 38F and clear skies. However, I always cover if the forecast is below 40F because I just sleep better.

We cover tomatoes outside the hoop houses with remay and boards keep the remay in place. We pull twine between the trellis posts to keep the remay above the tomatoes where it could get wet, touch, and freeze the plants. Photo by Evy Wallace.

Tip 4: Cover Up

Once you’ve prioritized which and how many plants you want to save, find covers you can use to keep frost off your plants at night. The idea with covering is to physically block dew from settling on your plants, freezing, bursting plant cells, and killing vegetative matter. The frost you can protect against is basically frozen dew.

Often the lowest temperatures will come after wind blows a storm through in the night. Your coverings must be able to withstand nightime breezes so you don’t have to get up at 3am to fix them.

What You Need
  • LIGHT WEIGHT, DRY coverings
    • Tarps or plastic sheeting
    • Remay, bedsheets or fabric
  • Weights or straps to keep covers in place.
    • Jugs or buckets of water
    • Boards or rocks
    • Bungees or ropes criss-crossed over covers

Testing out your frost protection system ahead of time is key. While their not pretty, I leave my coverings and weights right next to where they will be used so I can easily cover if the forecast unexpectedly changes.

uncover your plants & Keep covers dry

Especially if you use clear plastic, you can burn your plants up during the day if you leave the covers on. If you leave the covers on, the plants will get less light to ripen fruits. Also, keep the covers dry during the day. If you put wet covers on your plants, the covers themselves could freeze and freeze your plants.

Photo by FOX on Pexels.com

Tip 5: Melt Frost with Water

If the nighttime lows are forecasted to dip near 32F just before sunrise or you forgot to cover up, you can opt for spraying frost (frozen dew) off of plants before it has the chance to freeze plant cells.

In order to effectively melt the frost off and save your plants, you MUST spray it off BEFORE sunrise and continue to spray it off until AFTER sunrise.

The coldest temperatures occur after sunrise. Temperatures continue to drop until the sun is able to overcome the cooling of the earth. If you spray frost once but the temepratures are still below freezing, the water you added to your plants will freeze again. You have to use continuous water to keep the plants warmer and frost from forming. If sunlight hits tender vegetation with frost on it, it will blacken and die.

You can set up sprinklers around your garden and turn the sprinklers on in the morning or set them up on a timer to start before sunrise for frost protection. Just remember to drain your hoses every night so they are ready to use in the morning and not frozen themselves.

Photo by Anna Urlapova on Pexels.com

Tip 6: Observe Your Backyard Weather

Weather forecasts are general for your area, not specific to your garden. I have learned through the years that the forecast at my house is generally warmer by 5-9 degrees. That is to say if the forecast in Cove, Oregon is a low of 40F, it will be between 31-35F at our garden and may freeze. The forecast is perfectly accurate a quarter mile away at my friends’ house.

I have an indoor/outdoor thermometer and I keep mental track of the afternoon forecasted low versus the actual low at our house. Make sure you mount the outdoor thermometer near the ground where it is colder. Over the years, observation has allowed me to make the 39 degree rule–I will cover if the forecast is 39 or below. This rule just makes it easier to decide when to go to the enormous trouble of covering the farm.

I hope you are able to keep your gardens going through the nighttime temperature dips.

May we have a long, warm October.

Your Grateful Farmer,

Nella Mae

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