In the Garden:
New England
August, 2006
Regional Report

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Frosty fingers can damage even cold-tolerant spinach if it's left uncovered.

Weathering Frost

New England gardens may be heading down the home stretch but that doesn't mean New England gardeners are ready to call it quits. I for one am not ready to say goodbye to the beautiful dahlias, snapdragons, zinnias, and other tender flowers that have graced my garden all summer. Not to mention the peppers that are reddening, and the tomato plants that are trying to feed the neighborhood.

With that in mind, I'm beginning to go into frost protection mode -- locating the frost covers and sheets that I'll drape over plants on cold nights, and relocating tender annuals in containers to warmer microclimates next to the house or the stone patio. Here are some strategies I use to help extend the gardening season, both spring and fall.

Avoid the Low Spots
The best place to locate a garden of tender annual veggies and flowers is midway down a south-facing slope. Just like water, cold air flows downhill, to the valleys or low spots where it settles and chills the plants. Hilltops and mountaintops also tend to be colder because of the altitude and wind exposure. So plants growing partially down a slope have the best chance of surviving frost.

If the slope faces south, even better, because there the soil receives more of the sun's warmth during the day and can radiate this heat at night, warming the air around plants. I live on the side of a hill, and frequently my garden remains frost-free when the low-lying fields along the river are covered with a white blanket.

Even if your garden is on a slope, if you have any kind of windbreak -- trees, tall shrubs, a fence or other structure -- on the downhill side of the garden, this can trap the cold air around your plants and keep it from settling lower. Locate your garden where the cold air can move freely away from your plants.

Make the Most of Microclimates
I can extend the growing season of tender plants by nestling them against a south-facing side of my house, along a stone wall, or bordering my stone patio. These structures absorb heat and keep the surrounding air temperature slightly warmer.

When Frost is Predicted
Sooner or later you'll be facing a clear night (no clouds to hold in the heat) with little wind (cold air can settle over the ground) and temperatures expected to drop near freezing. It's time to grab your plant protectors (plastic tarps, sheets, frost covers) and go out before dusk to cover your plants. Polyethylene frost blankets can protect down to about 28 degrees, whereas the spun-bonded row covers only protect to about 30 degrees.

Since you're trying to capture the warmed air that radiates from the soil at night, make sure the protectors reach all the way to the ground so the warmed air can't escape. Anchor the bottoms with rocks or boards, and, if possible, prop up the protectors with tall stakes to prevent them from touching the foliage.

Humidity in the air can help prevent a frost because as the water vapor condenses during the night and forms dew on plants, some heat is released. This helps put the brakes on the drop in temperature. Without the moisture, the temperature drop is more rapid. To keep the odds in your favor, water your plants when a frost is predicted.

According to researchers at the USDA Agricultural Research Service, a coating of kaolin clay on plant foliage can help prevent frost damage. This clay, which is commonly used in paint, pottery, and cosmetics, has been marketed in recent years as a foliar spray to prevent insect attack. It's also been found to slow the freezing of water on leaf surfaces. It looks like a powdery coating but it washes off, and it's nontoxic. If you want to try it, spray it on your green tomatoes, which are more susceptible to chilling than the ripe ones!

Give It Up
Sooner or later the inevitable will happen, and night temps will plunge too low. You'll need to salvage what you can from the garden and kiss the rest of the squash blossoms goodbye (or pick them and batter and fry them!). Pick all green tomatoes. The small ones aren't likely to ripen so cook them up. The larger ones should ripen on a counter. Cover them with newspaper to trap the ethylene gas that the fruits give off, which hastens ripening.

If you haven't gotten around to repotting any herbs for growing indoors, do it now because they don't stand as good a chance of weathering the transition later in the fall. When the killing frost is predicted, pull up any herb plants left in the garden and freeze the leaves in ice cube trays with a little water for use in winter soups, or turn the basil into a quick batch of pesto.

For Frost Detection
If you like gadgets, there's a frost-detecting tool that can measure what's happening in your own backyard: a sling psychrometer. It helps you find the dew point -- the point at which moisture condenses out of the air to form dew. Generally speaking, if the dew point is 40 or below, a frost is highly likely.


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