Why did our frost only affect random plants?

Question

We had our first frost the other day (the growing season has been long this year).

Anyway, I noticed that some plants were seemingly randomly affected more than others. For instance, I have two Pepino melon plants growing right beside each other (which are free of spider mites, now, just for the record). The biggest one of them withstood the frost very well, and looks as healthy as ever, and the other mostly withered. I have three Rocoto pepper plants growing next to each other, and two of them withered right away, but the other took an extra day before it withered. Seemingly random parts of my Shark Fin Melon plants were affected severely, and seemingly random parts are just as chipper as ever. The tomatoes, at least, were consistent by the second day, with the exception of a couple small shoots on a few plants. The melons seem to have withered (with the exception of a few tips of the vines of the Red-seeded Citron watermelon). There are two tiny sweet pepper plants that are fine while the big ones are all wilting.

All my litchi tomato plants survived the frost (one had a regular tomato plant growing on top of it, which plant withered): I guess the litchi tomatoes must really be frost-resistant to some degree if that's the case; hopefully it's not just time-delayed frost damage (litchi tomatoes aren't tomatoes, by the way). The arugula is all fine.

EDIT: I've found that litchi tomatoes (Morelle De Balbis) actually are frost-tolerant. Mine was tolerant and evergreen to repeated freezes until it got to about 15° F. It must have natural anti-freeze in it or something.

I've heard if it's windy that it can protect plants against frost. I don't know if that's true, but do you think something like sporadic winds or varying phosphorus levels has something to do with the style of our frost damage?

Answer 1

Nothing to do with phosphorus levels - the usual explanation is varying exposure. One plant may shield another from the full effects, one might be further into a frost pocket and is thus more exposed than the one next to it, some plants are in a warmer spot to start with (more sun exposure, so the soil is warmer for longer, meaning frost has slightly less impact) or one plant is smaller and less able to cope with the onslaught. Subtle differences in location and size, when frost isn't really extreme, dictate how well a plant copes.

Windy conditions usually mean no frost at all, even if the temperature drops down really low. Frost itself flows like water, so lower points suffer more frost than higher parts - even three plants in a row with one further into the lowest point may have different levels of damage. Plants nearest to very open ground (not paved) will feel the effects of frost quicker than plants near buildings or within paved areas, because concrete and stone retain heat.

Anecdotally, my experience here in the UK, at home, is the effect of cold weather on three trees in a row on the front lawn, with one being nearest the open field opposite, and at the other end, nearest the building here. The one nearest the field goes red much earlier than the other three, because its more exposed, even though the trees are only about 8 feet apart, and planted at the same level. Equally, the Virginia Creeper which grows over the garage roofs (a long row of them) turns bright red at the furthest point, away from the buildings, and the nearest parts may not turn red at all, might just wither away, or turn red two weeks later. All down to exposure.