This berry is well worth growing as the flavour is intermediate to Blackcurrant and Gooseberry. However, it is a very big plant and requires a lot of space. Even with pruning, allow a 2 m x 2 m by 2 m high space. It is a true hybrid being a blackcurrant / gooseberry / ribes divericatum cross, bred by the Max Plank Institute in Cologne, and released to the Public in 1977. It is spineless and self-pollinating.
A good guide in identifying the Jostaberry apart from Blackcurrants, is to crush a few leaves in the hand. Jostaberry leaves have no scent, except a normal “leafy” smell. However, Blackcurrant leaves have a definite blackcurrant smell. In addition, Jostaberry flowers have a reddish tinge, as visible in the photo. Identification can come in handy if you take over an allotment or garden, and are not sure whether you have got a Blackcurrant or a Jostaberry.
The great advantage of the Jostaberry is that it is resistant to American Gooseberry Mildew, gall mite, blackcurrant leaf spot, and the White Pine Blister Ant. The fruits are the size of a large Blackcurrant, and are high in vitamin C. As it flowers early, it can suffer frost damage in frost prone locations, though I have never seen frost damage in Glasgow.
Plant it in fertile, well drained soil allowing a 2 m space all round. It may take a couple of years to produce a good crop of fruit, but eventually will produce large fruit crops.
The fruit will be fully ripe when it turns to a dark blue-black and each fruit has a slight “give” to it. Lift up the end of the branch with one hand and pick the string of berries with the other hand. As the fruit does not seem to ripen all at once, several pickings may be required in July and August.
Storage of Jostaberries. They will store for a few days in a fridge. For long term storage, try freezing and bottling, after preparing the fruit by rinsing and pulling off the stalks.
Suggested uses for Jostaberries, are in pies, crumbles, ice creams, jams, wine and liqueurs. More and more, I am finding that this is a more useful berry than Blackcurrants or Gooseberries.
Pruning. Remove weak and crossing branches in the early Winter, once the leaves have fallen and you see what you are doing. In the Summer, say in June, shorten the new growth to prevent the plant getting too big and completely out of control. This should also encourage the formation of fruiting buds for the next year. After several years, it may be a good idea to rejuvenate the bush by cutting out some of the oldest branches from the base, allowing new branches to grow and eventually fruit.
Pests and diseases as indicated previously, are not generally a problem, but do net against the birds.