Announcing itself with bright flashes of lightening and loud claps of thunder, a hailstorm fell tonight. What a racket it made. Our poor cat was cringing in a chair, his eyes wide, tail tucked under. I was thinking about the plants. There was over an inch of snowy hail in pots on the porch. It was dark and cold, but I dumped the stuff out of the pots of plants I know aren't hardy to frost.
I wasn't sure of a couple of plants, so went upstairs to check their hardiness. Sunset's Western Garden Book was the first reference I picked up. Sunset zones are great for understanding the climate you live in. But when I tried to find out whether a particular plant can take the cold temperature it was just exposed to, I had to see which Sunset zone it is hardy to, then look up that zone and read through the text about it until I found out its coldest temperatures. (Click on the pictures to see them larger.)
Doing this a couple of times made me realize the value of the USDA Plant Hardiness Map. Simple. Easy to remember. USDA Plant Hardiness Zones consist only of the coldest temperature a plant can survive. Zone 10's average coldest temperature is 30 to 40 degrees F, Zone 9's is 20 to 30, and so forth, each one 10 degrees colder. Once you learn the zones, you know the coldest temperatures without further reading. (USDA Hardiness Zones appear in many books and plant catalogs.)
You can see the USDA Plant Hardiness Map at http://www.usna.gov.Hardzone/ This is in the site of the US National Arboretum. Click on "Go to the Map."
In any case, I will report on the condition of the plants in my garden tomorrow. One thing I know is that the chard, wild onion, and garlic chive leaves will be marked with little white dots--injury caused by the hailstones. How did your plants fare in this weather?