Beat the frost when planning for tomatoes

It is mid-January and across the country serious gardeners are spending these cold, dark evenings poring over seed catalogs that arrive daily in the mail, dreaming about owning the bragging rights to summer’s first-picked tomatoes. For those of us who insist on growing our own transplants from seed, these dreams translate into serious planning around one central question: On what day should I sow the seed?

The goal is to have vigorous, sturdy, 5- to 6-week-old seedlings ready to transplant out after any chance of a late frost. Good planning depends on predicting the last frost date for your garden.

When I was a young gardener there was more certainty about such important issues. There was no shortage of old geezers who could predict the dates of first and last frost. All garden planning went forth from their pronouncement. Of course, when they were wrong you kept your transplants in the window for another week or so, watched them turn into pot-bound vines with pencil-thin stems that, once planted, spent the rest of the summer stunted, trying to catch up. Or you found yourself at the local farm store buying leggy transplants of standard varieties to replace those that were killed by a late freeze.

These days, if you call the local Cooperative Extension office and ask for the date of the last frost in your area, you get quite a different answer. You are given the probability of a certain temperature occurring after a specific date. For example, if you live in the Belfast area, the probability of your tomato plants experiencing 32 degrees Fahrenheit after May 9 is 50 percent, while the chance of the same temperature occurring after May 20 is only 10 percent. Probabilities can also be provided for experiencing low temperatures of 36 degrees and 28 degrees.

If you have Internet access, you can find this information in the same place that the Extension folks do:

http:/pmo.umext.maine.edu/apple/2004AllModels/Climate/FreezeDatesTable-ME.htm

This Web site also provides probabilities for the date of the first freeze and frost, useful information for selecting varieties that will mature and bear fruit within the limits of the local growing season. Again using the Belfast area as an example, the probability of 32 degrees occurring before Sept. 21 is only 10 percent, but the chances jump to 50 percent for Oct. 4 and to 90 percent for Oct. 18.

What has changed over the years? Planning for early tomatoes is still a gamble, but now we know the odds. To quote one of those old geezers, “You pays your money and takes your choice.”

Freeze/frost probabilities

Spring Fall

Station Temp. Probability Level Probability Level

90% 50% 10% 10% 50% 90%

Augusta 36 4/24 5/11 5/27 9/16 9/28 10/09

32 4/14 4/28 5/12 9/22 10/08 10/24

28 4/02 4/14 4/27 10/05 10/22 11/07

Bar Harbor 36 4/30 5/13 5/26 9/16 10/02 10/17

32 4/21 5/04 5/17 10/03 10/17 10/31

28 4/08 4/20 5/01 10/15 10/30 11/13

Waterville 36 5/11 5/25 6/09 9/06 9/18 9/29

32 4/29 5/11 5/22 9/17 9/29 10/11

28 4/15 4/26 5/07 10/05 10/17 10/28

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to reesermanley@shead.org. Include name, address and telephone number.