Are you sure they bolted? Beets are a biennial, never seen one bolt until their second year. They do get woody after being in the ground too long especially if stressed. April planted beets will rarely last through June. They like high pH but it is possible that your soil is too acidic (low pH) They do require water and reasonable fertility. Some varieties being more difficult than others.
{{gwi:27618}}

I have experienced beets bolting the first year. I read up on it and found that the most likely cause is the beets being exposed to a prolonged period cold (not necessarily below freezing) weather as seedlings. Since you seeded in April in the PNW, this seems reasonable.

Thanks, both of you. I can assure you that they're bolting. The prolonged-cold hypothesis seems likely to me because, even though some of them were volunteers (further evidence of first-year bolting) we had a miserably cold May and June.
I planted some early last July, however, and they bolted pretty quickly too. Also, I was backward about the PH. Our soil is acidic here, so it must be low PH. I'm thinking I should put some lime in the soil, too.