Every gardener knows what a late frost in the spring or an early frost in the fall can do to his prized plantings.
Among the more common victims at one end of the season are dahlias, tomatoes, iris, peonies, and peaches. In fact, practically any more tender flowers, vegetables, and fruits are susceptible.
Sometimes it means the destruction of the flowers before they have begun to fade or the fruits before they have fully matured.
Sometimes it means the destruction of the buds even before there have been any flowers or fruits at all.
In either case, it can be a thoroughly unfortunate occurrence.
It goes without saying that if, through some freak of nature, the temperature falls far below its normal range during spring or fall—say 10° degrees Fahrenheit or so below the critical point for the plants in question—not much can usually be done about it.
If, however—and this is what usually happens—it drops only 3° or 4° degrees Fahrenheit below the critical point, say to 26° or 27° degrees Fahrenheit, then something can be done about it.
A few of how frosts of this kind can be prevented from injuring your plants are discussed in the following paragraphs.
Infra-Red Bulbs
In trials at Michigan State College, dahlias were protected from injury at a 26° degrees Fahrenheit temperature using 250-watt infra-red bulbs spaced 5′ by 5′ feet apart over the planted area.
The infra-red bulbs should be set 3′ to 4′ feet above the tops of the foliage, and they should be turned on an hour or so before the temperature hits freezing to get a little head start in warming the plants.
Plants vary in the amount of frost they can tolerate.
A tender tomato, soft and spindly, just out of the greenhouse, hotbed, or cold frame, might quickly freeze at 26° degrees Fahrenheit even with the infra-red bulbs.
At the other extreme, some varieties of oats can stand 15° degrees Fahrenheit without the benefit of bulbs or anything else!
So the critical temperature, even with the protection of infrared bulbs, depends both on the species of plant and its condition, whether it is succulent and soft or woody and hard.
Needless to say, you’ll have a harder time protecting your plants on a frosty night that is windy than on one that is not. So a windscreen, in addition to the bulbs, may sometimes be in order.
Proper Installation Of Infrared Bulbs
Now, as to the installation of the infrared bulbs. As a starter, you may want to buy just one 250-watt infra-red bulb from your local electrical shop—they’re available in most shops nowadays for therapeutic uses—and an ordinary household extension cord.
Here are the following steps to do:
- Plug the cord into any regular 110-volt outlet in your home.
- Run the cord out a window or door to the garden.
Do these and you’re all set to start your first trial at preventing frost injury.
Remember, though, never use more than one bulb this way, or you may need the fire department due to an overloaded wire!
If you’re more ambitious, here’s how you can string five 250-watt bulbs around your tender plants:
- Starting at your central fuse box (not a mere wall plug), run two insulated No. 12 wires to the garden. This size will carry the power up to 100′ feet from the fuse box.
- You can use your own ingenuity when you suspend the bulbs. Overhead wiring is OK.
- Between the bulbs and your fuse box, you’ll need a switch. Ask your electrician for an externally operated, fused switch.
- Another thing, if raindrops should hit the hot bulbs, they’re likely to crack, so if rain is in prospect, you’ll be wise to rig up some little bonnets.
- Ordinarily, spacing the bulbs 5′ feet apart in each direction will be correct. Still, if you expect the temperature to go below 26° degrees Fahrenheit, it will be advisable to space them closer.
- The same will apply if the plants are especially succulent and tender—the closer and lower the bulbs, the more the protection is afforded.
Don’t try to save money by fooling with undersize wire, temporary switches, cheap sockets, etc., or you may burn your house down.
And, of course, it’s only safe to do the work yourself if you know your way around a fuse box. Personally, I’m terrified by them!
The Frostguard Idea
At the moment, the Frostguard idea only concerns large-scale operators, but the manufacturer had a home garden model.
Frostguard units burn kerosene and use large aluminum reflectors to radiate the heat back down to the plants.
They’re strange modernistic-looking contraptions, and one of them will protect ½ to ¾ of an acre. They burn 8 to 10 gallons of kerosene an hour.
As with the infra-red bulbs, the effectiveness of Frostguards depends upon the condition of the plants, wind, and so on.
At Michigan State College, tomatoes survived 26° degrees Fahrenheit for 4 hours under Frost-guard protection.
Reports from commercial growers are generally good, though variable. Quite a few of them are being used by vegetable growers in the Midwest.
The borne garden Frostguard, when available, will be operated by electricity rather than kerosene.
Lawn Sprinkles
Spraying plants with ice-cold water to protect them from frost may not make sense, but it actually does the trick.
Here’s how:
As soon as the temperature gets below freezing, turn the sprinkler on the plants. This will first wash the frost off the plants, and then gradually, a coating of ice will form on them.
This ice coating will afford some protection from the still colder air, and also, which is just as important when the sun comes up, the ice will allow the leaves to thaw out gradually without injury.
In most cases, frozen plants can be greatly helped if they are made to thaw out gradually.
This may be a somewhat messy frost protection system, but it is generally practical.
Of course, you’ll have to be careful not to overload tall, bushy plants with ice unless they are well supported, or they will be likely to snap off from the weight of the ice.
Also, be careful about shutting off the water when the temperature is below freezing—you might burst your hose.
Protection By Covering
As the temperature drops, heat moves out of the earth into the atmosphere. Scientists tell us that the earth will lose a million B.T.U.’s per acre on a cold night.
If you spread a little loose straw, newspaper, burlap, or what have you, over your plants, you’ll trap a few of those B.T.U.’s, and this heat will go a long way toward protecting your plants from frost damage.
Then, the following day, this covering material will keep off the direct sun and let the plants warm up gradually. It’s the same principle here as with the sprinkler system.
An adaptation of the protection by covering idea is the Hotkap, a device used quite extensively by commercial growers in various parts of the country.
Hotkaps are little cones made of translucent paper placed over seedlings after they are transplanted outdoors. They act as miniature greenhouses.
Hormone Preparations
Within the past few months, reports have come from California stating that a new hormone material, designated “Horms No. 4,” has been found valuable in alleviating frost damage in plants.
The material is said to be a compound of vitamins and hormones and is reported to have lessened the severity of frost damage through pre-treatment and to have aided recovery through post-treatment.
Grown under otherwise identical conditions, treated tomatoes are reported to have lived and untreated ones to have died.
Since these are only first reports on the use of hormone preparations for frost protection, and since the materials are still in the experimental stage, some time will have to elapse before anything of a general nature can be said about them and before they become available for commercial and private use.
Conclusion
There are lots of ways, you see, to prevent your prized plants from freezing.
The most important thing is to be on the alert for approaching frost.
Taking that for granted, it doesn’t much matter which protection method you choose.
As they say in the army, the thing is to do something.