Get better jostaberries

Several years down the line we have a large, vigorous shrub whose fruit are less plentiful than that of a gooseberry or blackcurrant.

Q Having read that jostaberries will grow in the shade, I planted a bush in a north-facing position about seven years ago. How can I persuade it to set a better crop of fruit?

Angela Hawkins, Stroud, Gloucestershire

A The thornless jostaberry (correctly pronounced ‘yostaberry’) is a hybrid created between blackcurrant and gooseberry. I was also attracted by the promise of picking sweet berries from disease/thorn-free bushes.

Although sweet enough to eat raw, the berries seem to lack the distinct flavor of either parent. On the plus side, the plant is healthy, sets fruit well on its own (with insect pollination), is vigorous, and responds well to pruning.