How to Grow Grapes: Prune Hard, and Prune in Winter

There is one thing to understand about grapes, and everything else follows from it: fruit comes on shoots that grow this year, from buds on wood that grew last year.

That means every winter you cut nearly all of last season’s growth away. People find this alarming and prune timidly, and the result is always the same — a magnificent vine with almost no grapes on it.

Site and soil

Grapes want sun, heat and shelter, and they want them more than almost any other fruit you can grow in a temperate garden.

A south or south-west facing wall is ideal — it adds heat during the day and radiates it at night, and in a marginal climate that is often the difference between ripe fruit and sour fruit. Under glass is better still.

Soil should be free-draining and not rich. This is the counter-intuitive part: grapes are deep rooted and thrive on stony, poor ground. Rich, moist soil gives you vigorous leafy growth, poor fruiting, and more disease. Vineyards on gravel are not making a virtue of necessity.

Support first

Build the structure before the vine goes in, because it will be there for thirty years.

• Three or four horizontal galvanised wires, spaced about 12 inches apart, lowest at roughly 18 inches.
• Strained tight between posts, or on vine eyes if you are training against a wall — the eyes hold the wire a few inches off the surface, which is important for airflow.

The first two years: build a trunk

1. After planting, cut the vine back hard to two or three buds. This feels destructive and is correct.
2. Let the buds shoot, then select the single strongest and remove the others. That shoot becomes the permanent trunk.
3. Tie it in as it grows, and pinch out side shoots.
4. Remove every flower in years one and two.

A vine allowed to fruit in its first two years never builds a decent framework, and it pays for that for the rest of its life.

Winter pruning: the annual reset

For most garden vines, spur pruning is the right choice. In midwinter, cut every shoot that grew last season back to one or two buds from the permanent arm. You are left with what looks like a bare skeleton with stubs on it. That is correct.

Summer pruning is a different job

Winter pruning sets the structure. Summer pruning controls light and energy, and it is what actually ripens the fruit.

• Thin the shoots in spring when they are a few inches long, leaving them 6 to 12 inches apart.
• Pinch each fruiting shoot back to about two leaves beyond the bunch.
• Shorten side shoots to one leaf.
• Remove some leaves shading the bunches in late summer — but not all of them, since the fruit can scorch in strong sun.

The purpose is not tidiness. Every leaf beyond what the bunch needs is competing with it, and shaded bunches do not sweeten.

Thinning and harvest

Remove surplus bunches so the vine ripens what remains — one or two per fruiting shoot is a reasonable target for table grapes. A vine carrying everything it sets ripens none of it well.

For dessert grapes, thinning individual berries within a bunch with narrow scissors gives larger, less congested fruit that does not rot in the middle. It is fiddly and it works.

Harvest by taste, not by colour. Grapes stop accumulating sugar the moment they are cut, so there is no ripening on the counter. Colour changes weeks before the sugar arrives. Taste a berry from the bottom of the bunch, which ripens last.

Common problems

Powdery mildew — white dusty coating on leaves and fruit. Airflow, summer pruning and resistant varieties. See powdery mildew.

Downy mildew — yellow oily patches above, white growth beneath, in wet weather. Improve airflow; avoid overhead watering.

Botrytis — grey mould in dense bunches. Thin the bunches and remove shading leaves.

Birds and wasps — net the bunches, or bag individual ones, from the point where they begin to colour.