
Growing up in Ireland, I had the pleasure of first going "blackberrying" at age 7 in a country lane lined with rows and rows of bramble bushes filled with the juicy dark fruit.
In San Francisco, blackberry bushes are few and far between. It may have something to do with the foggy weather, or just the fact that there is not a lot of open space. I saw a woman picking blackberries on the trail from Fort Mason to Aquatic Park one year, but I've never associated Bernal Heights with blackberries.
Well, I'm happy to report there is quite a big and healthy bramble bush with both sweet and unripe berries on Bernal Hill. Walk in past the sign on the north side that says "Bernal Heights Park" on Bernal Heights Blvd. (there is also a small parking lot there and a wooden bulletin board with local notices). Just opposite the board, there is a big, tangly bush with surprising amounts of fruit available. Perhaps the hawks keep the type of birds that would feed on these berries away?
Looks like the berries will be ripening and available for picking for another few weeks. But if you want to make jam, get thee to a farm where you can pick as much of your own fruit as you need.