What Average Frost Dates Mean

What Average Frost Dates Mean

Posted by subu9213 | On :March 10, 2013 | No Comments


Let’s talk frost dates.

All seed packet planting instructions tell you to sow seeds x number of days before or after your last frost date.  Of course, nature isn’t as strictly punctual as we’d like, so such a date is an average, and the window of safety may be worse than you think.

Cool weather plants, like spinach, peas and broccoli, are cold and frost tolerant, but hot weather plants like squash, melons and tomatoes are not.  Put them out too early and a low overnight temperature will kill them (unless you take extraordinary measures to protect them).

Tomatoes are very sensitive to cold.  Therefore the instructions are to put them out after threat of frost has passed.  But when is that, exactly?

My friends and mentors in Waxahachie give the date of March 18 as the earliest date to set out your plants.  The average Spring frost date in McKinney is March 20—but what that means is there is a 50/50 chance you will still suffer a frost on that date.  Are you comfortable with that?  I’m not!  In fact, based on historical records, there is still a 10% chance of the temperature dropping to freezing sometime before April 9.  By April 10, however (from an historical perspective) there is no threat of it freezing.  That’s still not a guarantee, but close enough!

Nevertheless, waiting until April 10 to put out tomatoes seems awful late.  David L in Plano (whose tomato photos I forwarded awhile back) puts his out on April 1.  Given his overwhelming success over several years, I plan to follow his lead—and I recommend it to you as well.

Gambling by setting tomatoes out early won’t buy you much anyway, actually,because they need warm soil to thrive.

You can type in your own zip code at http://davesgarden.com/guides/freeze-frost-dates/#b and see the averages for your specific area.  There are enough “micro climate” differences, even within the DFW area, that it might be worth checking.

Of course, given the overall warming of the planet, calculating averages based on records that don’t go so far back might provide a more accurate picture….

Remember that tomatoes won’t set fruit once it gets too hot—and too hot can come too soon in Texas.  To give yourself the best chance of success, you want the most mature plants possible to set out on April 1.

All this is on my mind because for the past several weeks a number of people have told me about what they’ve planted, or plan to plant the coming weekend, and I’m amazed that they seemingly haven’t actually read anything about when they are supposed to plant.

Please refer to the Garden Bible for recommended dates of what to plant to when.


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