Not a literal rabbit hole, instead, the one that I encountered when just for fun I looked into sunburned leaf damage, like what appeared today on a single squash leaf. Sunscald during hardening off isn’t what you’re aiming for, but it happens and it’s never been a big deal. So long as the seedlings are well-watered and the roots aren’t getting cooked in their containers, they’ll be fine has been my experience. Still, since only one leaf among around three dozen squash and melon plants got burned, after several full days in the sun, and yesterday half overcast, I took a mild interest—if I was a lot busier, with hundreds or thousands of seedlings on the go, and everything else looked fine, it wouldn’t get a second thought. Odd one-offs happen all the time.
A bunch of reading and skimming of farm and garden blog posts, university agricultural extension papers, science mag articles, and scientific studies, and no answers. The sunburn itself seemed unusual, especially after a half-cloudy day. Of course, our SPF sunscreen-and-skin cancer training has told us that UV is still strong on cloudy days, but why did only one leaf get so toasted?
Then I discovered the UV spike. Not so widely written about, not as confidently stated as ~80% of UV makes it through clouds, but a real thing. When certain types of cloud pass in front of the sun, like perhaps the fluffy cumulus ones that floated by most of yesterday, the fringes of said clouds can act as a magnifying lens or filter that focuses and directs UV straight down, resulting in an intensity spike of maybe 25%. Could it be that one big early leaf hadn’t been shaded by the others on previous days and gotten more exposure and hidden damage, and just couldn’t take a day of high-powered UV micro-blasts, a few seconds each as the sun disappeared and reemerged, over and over. Hmm, that sounds maybe fairly reasonable…
Soon after, I lost interest—WHY would I want this explained? I could think of no good reason. I’ve found with tiny farming that learning is continuous and great, but what you choose to take in is also critical, sucking up everything is a waste of attention. The one burned leaf isn’t a mystery, it just clearly happened. And unless more similarly unusual things appear, I’m not particularly curious. The real thing to remember: harden off, a couple hours max outdoors the first day, and keep them well-watered and not boiling in their pots! When they get into the real ground, small ups and downs along the way will be forgotten, they’ll spread their roots and do just fine. Conditions in the field being favorable, of course!
