Heat Wave

Early September heat wave! Temps are forecasted in the 90s all this week, after a pretty mild August. We still have a good amount of stubborn green peppers and green tomatoes in our greenhouse, so hopefully these hot days will encourage them to ripen up.

Heat can be tricky for leafy crops, though. First there's the issue of harvesting them before the day gets too hot. On a cool or cloudy day we can harvest leafy greens any time, but on a hot sunny day they really need to be cut before 9 or 10 am, so if we start at 6:30 it only gives us a window of a few hours to get it all out of the field, washed, and in the cooler. On that kind of day we can spend the hotter part harvesting non-wilty crops like tomatoes, peppers, eggplant, carrots, etc. Or just weeding, planting new stuff, or any of the million other things there are to do on any given day on the farm.

The next problem with heat is that the leafy plants get stressed. The laid-back leafy guys like kale and chard don't mind much, they can just wait until the next cool morning. But lettuce is pretty high-strung and if it gets too hot it will bolt, meaning it's transitioned permanently from the leafy growth stage of life to the reproductive seed-forming stage, making it tough and bitter. So we'll need to cut the nice baby lettuce leaves we have this week first thing Monday morning to prevent that from happening.

Another problem with heat has to do with row cover. These are large pieces of white cloth that we put over the plants that have very small holes like a screen, so that light and rain can get through but not bugs like flea beetles and cabbage moths. It also makes the plants hotter though, which can be an advantage if a frost is coming but a liability if the weather gets really hot. Lettuce doesn't need row cover because bugs don't like it, but cabbage family crops like kale, collards, arugula, and mustard greens do need that protection, so they sometimes need to be uncovered to prevent bolting or heat stress that leads to a very bitter taste (or in the case of arugula a too-spicy taste).