Home > Great Big Greenhouse Blog > March 2016 > BONNIE'S GARDEN--Our Last Frost Date is ???

BONNIE'S GARDEN--Our Last Frost Date is ???

Little summer vegetable plants are starting to show up now.  It’s March, for Pete’s sake, still, I’m forever trying to get an earlier tomato and I already have tomato seedlings about five inches tall in my sunny spare room window.  So when is it safe to put them out?

Here in Richmond, you’ll usually hear people say our last frost date is April 15th.  But is it?  According to the UVA Climatology Office, we have a 50% chance of having a frost on or after April 6th.  We have only a 10% chance of having a frost after April 23rd.  The problem is:  Mother Nature can’t read!  We’ve had a frost as last as May 11th before and, the past couple of years, have had frosts AFTER April 23rd.  Because I've been "caught" before by a sneaky last frost, I think of May 1 as fairly safe.

It’s not just the air temperature.  We also have to consider soil temperature.  Beans, cucumbers, squash, and corn all prefer soil temperatures of 65 degrees or better.  When soil temperatures are cooler than that, the seeds take much longer to sprout—and your germination rate will go down. 

Years ago, when I was in school, we did an experiment where we planted cucumber seeds in a pot outside the first week of April.  We covered the seeds at night, in case of frost.  We planted more cucumber seeds the first week in May.  By the time school was out (the first week in June), the two batches of seedlings were the same size.  The ones started a month early were no bigger than the ones started in April!  My professor’s way of making a point that earlier is not always better.

That doesn’t mean that I don’t take my vegetable seedlings out on nice days.  I do.  I even leave them out if night temperatures aren’t supposed to get below 55 degrees.  I’m just prepared to bring them back inside (they spent the past weekend inside the whole time.)

If you have row covers, hoop houses, or those little “water-towers” to protect your plants (or don’t mind running about covering plants at eleven o’clock at night), then plant tender veggies whenever you want.  I’m going to take the lower stress road and wait until May 1.
Posted: 3/22/2016 by Bonnie Pega | with 0 comment(s)
Filed under: bonniesgarden
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