Answer: French sorrel is a cool-season herb, so when temperatures begin to rise it "bolts," just like your other greens. Once greens start bolting, they're usually not too tasty, but that's up to you.
There are sorrels that are annuals, but most sold as "French sorrel" are perennial, so it should come back in the fall. Cool season herbs can look brown, woody, and almost dead during the summer, so give it a chance before pulling it out. Use several inches of mulch to help keep soil temperatures low. If it doesn't make it in your particular growing conditions, you can always treat it like an annual, and replant in the fall. You're right--it is a wonderful herb, but not many people seem to know about it!
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