Last night and this morning brought the first serious frost of the Winter to this part of the Desert Garden. Air temperature dipped down to around 30° here at The Ranch, but it didn't last for too many hours, and there was little damage to the Winter crops; the peppers, chiles, and eggplant, however, are on their way out after many months of good service.
Our little broad bean and his band of brothers looked pretty bad. The top picture to the left was taken just before dawn, and the plant is clearly frozen; the dark, wet-looking green to the top is a typical sign of frost, and the silvery coloration on the lower portion of the plant is ice crystal reflecting in the camera flash.
Fortunately, one of the things that makes the Fava Bean a good choice for the Winter Desert Garden is that it is fairly frost-tolerant; I would call it moderately hardy. In a light frost, as we had last night, it should recover just fine. If we were expecting a harder, longer freeze, I would give it some frost-cloth protection.
Most of the cool-season vegetables that we grow in the Desert Garden have some degree of hardiness, and will take at least a moderate frost, but the stage of plant growth can make a difference. Peas, for instance, are very hardy as seedlings and plants, but the flowers and pods are fairly frost tender. If you go out some frosty morning and find that your pea pods have a wet, dark green look to them, as in the foliage of the broad bean, above, your best bet is to harvest them right then and have them for breakfast. An even better idea is to protect them the night before.
Lettuces and endive can vary greatly in their hardiness, depending on variety. If you forget to put frost protection on your leafy greens and they freeze, here's an interesting trick you can try: cover the frozen plants first thing in the morning, before the sun hits them; anything that shades the leaves from the sun will work. Then, once the air temperature has come up well above freezing, remove the cover. It seems that frozen lettuce leaves that thaw suddenly, as when the sun hits them, will wilt and die. But frozen lettuce leaves that warm up slowly, as the air warms, will often recover and be fine.