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Wednesday, March 15, 2017

Man in Overalls - Back to Basics: What to Do When it Freezes in N FL

Planning for Spring
I'm writing this quick note to let you know about the probable freeze tonight in north Florida. Here's the short version: If you've got tender warm-season plants growing (think tomatoes, peppers, cucumbers, squash, and the like), water thoroughly and then throw a sheet over your warm-season veggies & tropical fruit trees (especially if they've only been in the ground 1-2 years).

I can't count how many people I've met who have a complex about "killing plants" and who think, "I don't have a green thumb." What they don't realize is that anyone (EVERYONE!) who grows their own groceries is well-versed in killing crops (myself not-withstanding). Why do you think there are entire USDA funding streams for crop loss insurance and crop-loss loans? Even the best of farmers-- much less gardeners-- inadvertently kill things from time to time.

On the topic of freezes, a few years back (2010 I believe), I was up late organizing a kids food gardening workshop when I suddenly remembered it was supposed to freeze that night. Being 11pm or midnight already, I googled the temperature and discovered to my chagrin that it was already 27 degrees outside! I had some beautiful lettuces I had intended to harvest, so I rushed outside with a knife and a flashlight. Sure enough, the lettuces were crispy and frozen. I cut the largest ones and hustled back inside where I attempted to "save" the frozen lettuces by thawing them in running water. They melted into a mushy slime like I'd thrown them in boiling water. Ruined! (Mind you, I did this after I had "hung up my sign" as they say. I was, at this point a "professional food gardener.")

Resigned by my failure, I went to bed. The next morning, I went outside to inspect the rest of the lettuces (and other cold-season crops)-- expecting total crop failure. Much to my surprise, all the smaller lettuces (which I had not attempted to save!) had thawed slowly via sunlight filtered through the pine trees towards the east and had gone right on growing without a hitch: all fine! How did that happen!?

And then I remembered: cold-season crops (see my "What Can You Grow in a Square" resource for a list) are actually able to freeze solid and unfreeze (assuming the temperature isn't down past 25) and go on growing just fine. The trick is the thawing. If they warm up slowly, their cells do not burst. If, however, whether by a flash-unthawing by water or by overly-warm direct sunlight right at dawn, the plant's cell walls crack and burst resulting in a destroyed crop. This is a large part of the reason why farmers cover cold-season crops for freezes with row cover; it's not so much that it keeps their crops warmer (though it does, barely). The real value of row cover is that it slows the warm-up process, so the plants are not flash-melted by the warming dawn sunlight.

But all that ^ is only about cold-season crops, which is not the cause of worry tonight. They'll be fine.

Warm-season crops, on the other hand, are vulnerable to any and all temperatures under 32 degrees. So if you have crops growing late into the fall/winter (next year) or you've already put out spring plants and we get a late-season light spring freeze (like tonight)...
  • If you're close to the River or downtown/near lots of concrete or your garden is somewhat sheltered from the north or your garden is on a slope, you'll probably be okay, but just to be safe....
  • On the other hand, if you're further from the urban core or your garden is in an open field or it has no protection from the north or your garden is in a low spot, you'll almost definitely get some freezing temperatures, so...
Either way, you should do at least the first of these two things:
  1. Water thoroughly before nightfall. Most freeze damage is caused by dehydration.
  2. Cover the most vulnerable or most tender warm-season plants (and tropical fruit trees) with a blanket, buckets, or something else to keep a small insulated air pocket to protect your plants. (Don't worry about yet-to-sprout seeds. They're protected under the soil).
If you're a visual learner, here's the same basic info in my How-to video I did with the FL Dept of Ag:


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PS- if you (or someone you know) is interested in subscribing to my "Overalls On Call" seasonal Food Garden Tips, Advisories, and Q&A Support by text, email, or video-- which will include  advisories-- I'm going to be beta testing it with a handful of customers in the next few weeks. The price tag is $25/month. (If you're signed up for a maintenance plan, you'll get this included)

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