There are five primary ways that a home gardener can hold Jack Frost at bay IF the temperature dip isn’t extreme. It isn’t possible to beat a 60 mph –30 F. arctic blast outdoors. Don’t even try. But you can sometimes stretch the growing season by several weeks with a judicious application of some simple techniques.

When the sun goes down, cold air that had been suspended in the atmosphere on a pillow of warm air nearer the ground is free to fall. This happens all year around and is part of what gives us the cooling at night in the summer.

This cool / cold air pools in low spots. Warm air is replaced by cool air, then cold air, then colder air. That low spot always ends up with the coldest air available. If the air is cold enough and if our garden is in that low spot, frost forms on our precious veggies and flowers. So, here are 4 tactics to defeat this phenomenon that are suitable for the backyard gardener.

Siting

Before you even plant your garden, before you turn the first spade of dirt, give some thought to where the cold air of an autumn night might pool. Imagine it as a heavy rainfall and mentally calculate how high the waters might rise before they would flow out to somewhere else. Plant your garden well above that point. Also, use the beds nearer the bottom of this space for less cold-sensitive plants. For instance, the flavor of cabbage, Brussels sprouts and broccoli all seem to be improved by a light frost. Slow germinating seeds are safer here than a tender transplant would be. In the fall, root crops will be less damaged than top-fruiting plants and garlic would absolutely love such a location. As they say, “several years of hard experience can often substitute for a few minutes of hard thinking.” And, I might add, vice versa.

Construction

In flat areas you can accomplish the same goal by raising the beds. The higher you raise the bed, the more ‘insurance’ you buy against both late spring frosts and early fall frosts. This is because the air will pool below the top of the bed. The further below the top, the greater the total volume of cold air that can be accommodated before damaging frost occurs.

Air Flow

Here’s where we get ‘high tech’. If the air does not sit, some warmer air will get mixed in with it. So it only makes sense to keep the air moving if at all practical.

This can be accomplished by simply setting an ordinary box fan / window fan in the garden, pointed away from the plants. Best use I’ve found is to put the fan(s) in the middle of each row, all facing the same direction and all cocked a little upward and out of the bed area. If this description is confusing, just point the fan anywhere except directly at the plants.

Unless you have several braziers at your command, their value is that the heated air rising from the charcoal also sets up a gentle wind current that keeps the cold air from pooling.

Add BTU’s

Charcoal braziers, small wood fires, electric hair dryers or space heaters are all pretty obvious sources of additional heat that can be used when rain is not expected. (If it rains, frost will not form, although ice may.)

Less obvious is a light mist of water from the hose. One thing we can be certain of is that, while the water may be cold to the touch, it is warmer than 32 F. – or it would not flow through the hose. This is probably the hardest method to implement because it either uses up a lot of water or it must be manually attended during the cold of the night. However, if you can’t fire up the braziers or the extension cord won’t reach far enough, it will usually work.

Shelter

In the spring, it is wise to have some cloches, hot kaps (a commercial, lightweight, vented cloche), large jars or old newspapers available to protect your plants. Make a tent of the newspaper in mid-afternoon to allow some heat to build up by securing the edges of the paper with loose soil or boards. Close the ends of the tent to keep the heat inside through the night. Wait until the frost has left the ground naturally and the air has warmed up substantially before removing the newspaper … even if this should take a day or two.