Pruning Blackcurrants: Take Out a Third of the Oldest Stems Every Winter

Where the fruit actually comes from

This is the fact the whole system rests on. A blackcurrant carries its heaviest crop on shoots that grew the previous summer. Two-year-old wood still fruits, but less, and with smaller berries on shorter strigs. Three-year-old and older wood carries very little worth having, and it takes up light, air and root energy that the young shoots need.

That makes blackcurrants completely different from red and white currants and from gooseberries, which fruit on short permanent spurs on a framework of old branches and are pruned to keep that framework. Prune a blackcurrant like a redcurrant, by shortening side shoots back to spurs on permanent branches, and you will cut off nearly all next year's fruiting wood while preserving the old stems you should have removed. It is the single most common mistake made on this plant.

If you inherit a bush and cannot tell which currant it is, crush a leaf. Blackcurrant leaves have a strong resinous smell that red and white currants do not. Prune to what the plant is, not to what the label says.

Telling old wood from young wood

You prune on stem age, so you have to be able to read it. Age shows in bark color and texture and in how much growth the stem made last summer. In the dormant season the differences are obvious once you have looked at a few, and they are far easier to see with the leaves off, which is one reason winter is the right time.

Work from the base of the bush, not the top. Follow each stem down to where it comes out of the ground or out of a low fork, and judge the whole stem by its oldest section. A dark, flaking stem with a young shoot on the end is still an old stem.

The winter cut, step by step

Prune in the dormant season, once the leaves are off and before the buds move. Late in the dormant season is fine and has one advantage: by then any buds swollen by gall mite are obvious, and you can take those stems out first. Use loppers or a pruning saw for the thick stems and pruners for the rest, and expect to remove a genuinely large pile of wood from a mature bush.

The target on an established stool is to remove about a third of the stems each winter, always the oldest ones, cutting them out flush at ground level rather than leaving stubs. Done every year, that means no stem is ever older than about three seasons, and the bush renews itself indefinitely from the buried buds you created by planting deep.

1. Take out dead, broken and lying-down stems first Anything dead, snapped, or arching so low that the fruit would touch the soil comes out before you start counting. This clears the view and often does a good part of the job on its own.
2. Identify the oldest third Look at the base of the stool and pick out the darkest, roughest, thickest stems. On a mature bush of nine to twelve stems that will be three or four of them. Mark them with a loop of string if it helps you keep track.
3. Cut them out at ground level Take each one right down to the soil, or to a strong young shoot low on the stem if there is one. Do not leave a 6 inch (15 cm) stub: stubs die back, harbor rot, and produce nothing useful.
4. Open the middle Remove any remaining stem that grows through the center or crosses another. You want an open, goblet-shaped stool where light reaches the base of every stem and air moves through the middle.
5. Leave the young shoots alone Do not shorten the strong new shoots that came from the base. Their whole length is next year's fruiting wood. The only tipping worth doing is trimming a weak, whippy tip that would bend to the ground under a load of fruit.
6. Clear and mulch Rake out every prunings and fallen leaf from inside the stool, then mulch generously with compost or rotted manure over the root area. Old leaves left in the crown carry mildew and leaf spot through to spring.

Burn or bin prunings from any bush with swollen buds or with mildew on the shoot tips. Do not shred them into a mulch that goes back under the bushes.

The first three years are different

A young bush has no old wood, so there is nothing to renew yet. The job in the early years is to build the stool: as many strong stems from below ground as the plant can make. That means cutting almost nothing, and feeding and watering hard so the shoots come.

The one exception is the cut at planting, when the whole bush goes back to two buds above the soil. After that, hands off, apart from removing anything weak, damaged or lying flat.

Renovating a neglected bush

An old bush that has not been pruned for years is a mass of black, flaking stems with a few short strigs at the top and nothing at the base. Provided the stool is healthy, it can be rebuilt, because the buried buds from deep planting are still there. Cut the entire bush to within 2 inches (5 cm) of the ground in the dormant season, feed heavily with nitrogen in spring, mulch, and water through the summer. You lose one crop entirely and get a full one two summers later.

Alternatively, spread the work over two winters: take half the stems to the ground in the first winter and the rest the following winter, so you keep a light crop throughout. That is gentler on the plant but slower to give you a properly renewed stool.

Do not renovate a bush that has swollen buds or has been showing reverted, narrow-lobed leaves and near-empty strigs. Those plants carry a virus that pruning cannot touch, and the correct action is to dig them out and start again on fresh ground.

Record how many stems you cut out of each bush and how many new basal shoots came the following summer. If a stool consistently gives fewer new shoots than the number of stems you removed, it is losing ground, and it needs more feed, more water and a heavier mulch rather than more pruning.