I've grown boysenberries in DC for several years; they are one of many rubus (blackberries, raspberrries, etc.) hybrids. every berry I've harvested (not many; they don't seem well adapted here) has been mouthpuckeringly sour, no matter how ripe. perhaps loading them up with syrup would help! I throw mulch over the canes in winter, as I suspect they're marginally hardy in zone 7.

If you are interested in berries or other edible plants, but don't have much experience growing them, I recommend that you start by looking at Edible Landscaping of Afton, Virginia (near Charlottesville). They specialize in edible plants that are well-suited for the Mid-Atlantic climate. Also, they provide potted plants, not just bare-root like some other edible plant nurseries. They don't carry any boysenberries, but in Rubus (blackberries, raspberries, and other brambles) they do carry: thornless and thorny blackberry, "wyeberry", red and black raspberry.

(Only please don't order the wineberry, it's very invasive and I can assure you we have enough already, also the stems are nastier to touch than any other Rubus.)

Here is a link that might be useful: Edible Landscaping

got mine from Burnt Ridge nursery online. I searched and they have great ratings (on Gardenwatchdog) and low prices. My whole order was excellent and the only thing that will prevent me from ordering from them year after year will be lack of space for planting..

No, I have no affiliation.

Here is a link that might be useful: Burnt Ridge Nursery