We're getting a cold snap in May after the cold spring, and was wondering how cold eggplants can go while still surviving.
It is difficult to say. Humans feel temperatures differently than a thermometer, but also the plants do not feel temperatures like thermometers.
If it is just a very short period, and then suddenly normal temperatures, they survive without problem (I have sometime hail, which is ice). Soil store heat (and release heat), so after a hot period, a short period of cold is not a problem. People forgot that temperatures that we measures are made at 2 meter height, in a typical field. Plants usually lives in microclimate which much different temperatures an humidity. (temperature near soil is often much higher as well the humidity).
But aubergines in May, ... this is a critical period, and probably you did have enough heat before this cold. I also do not know how long you had the freeze and how humid it was, nor how big was the plants.
If it happen to me, I would prepare a contingency plan: I would buy new aubergines (the number depends on how bad I estimate the aubergines suffered). The actual aubergines probably will survive, but probably most of leaves will fall in next weeks, and you will have new sprout from the stem. Not all is lost, but this will delay the harvesting (and less aubergines). For this reason you should add few new plants.
There are a few conditions to consider with temperature and fruiting plants.
- Below a certain temperature, fruit will not set on a flower. For eggplants this threshold seems to be night temperatures below 50 degrees Fahrenheit. However, the plant can still live, new flowers will form, and those new flowers can produce fruit.
- Below a further temperature, the plant can of course end up dying or being severely damaged. It seems likely that a 33 degree Fahrenheit night could put the plant at risk, at least according to the Texas A&M Extension.
So, what should you do? If the cold-snap is short, a little season extension trick should get it through and let the plant survive. If you have a cold frame (or have always wanted an excuse to build one) then use it! You can build a temporary protective structure, like a section from an old tomato cage that is cut to be just taller than the eggplant, and then put a blanket over the cage. 2 or 3 layers of bubble-wrap could also help if you have some extra bubble wrap.
You can also try adding heat into the space: some rocks that get heated by the sun during the day, a warm water bottle, a string of christmas lights (the old incandescent ones that give off a little heat).
I have used patio lights inside of a low "poly tunnel" (photo below) on a night that had snow. My tomatoes survived and it gave a real eery feeling to the backyard for a little :) I don't suggest you necessarily do this, just sharing it as an example that works if you want to try more season extension.