I planted a dwarf everbearing blackberry ("Baby Cakes" cultivar) in a container this past spring. After growing vigorously through the summer to fill a 30-35 gallon trough, it flowered voluminously on the primocanes in the fall, but none of the flowers developed into fruit.
Why might this have happened, and is there anything I can do to encourage fruiting in the future? I have read that blackberries can suffer from incurable "sterility," in which plants reliably flower but never fruit. Is that a likely explanation in this instance?
Additional (possibly irrelevant) background: I am in zone 7a. The plant is on a roof deck in full sun. There is abundant pollinator activity where it is planted, although the blackberry plant does not seem to be the bees' favorite. Right after that plant was planted in the spring, it produced a single bloom on a floricane, which did develop into a berry.
UPDATE: With the benefit of another growing season of experience, it is clear that the plant is not sterile. In the spring/summer after I wrote my question, the bush set abundant fruit.
However, it once again did not produce much fruit in the fall. The blooms from the late summer/early fall generally failed to develop into fruit. In the mid-fall, a decent number of blooms did start to develop into fruit, but those fruit were a week or two short of maturity when the cold weather hit. This seems possibly consistent with the theory given below that the plant is not truly everbearing in my climate, at least when it is young, although its modest success in setting fruit this past fall could be a good harbinger for future years.