You prune grapes in summer by regularly removing the laterals (the side shoots growing out of the leaf axils), pinching out the tips of the fruiting shoots, and thinning the leaves around the bunches. That gives the bunches more light and air, they ripen faster and sweeter, and mildew gets far less of a chance. Start in June and repeat every two to three weeks into late summer.
Sounds like a lot of work? It is not that bad once you know what to look for. In this article I will walk you through exactly what you cut off, what stays, and when. With practical rules of thumb, the differences between a greenhouse, a wall and a pergola, and the mistakes most people make.
Summer pruning or winter pruning: what is the difference?
You prune a grapevine twice a year, and those two rounds do completely different jobs.
Winter pruning is the structural prune. You do it when the plant is bare and dormant, roughly from December to mid February (so before the sap starts rising). You cut the fruiting side shoots back to two buds (“eyes”) and that sets the shape of the plant and the places where next year’s bunches will hang.
Summer pruning is green pruning. Here you cut away soft, growing shoots and surplus leaves while the plant is in full leaf. The aim is not shape but ripening: you steer the energy into the bunches instead of into leaf, and you make sure light and air reach the grapes.
In short: winter pruning decides how many grapes you get, summer pruning decides how good they turn out.
Why does summer pruning matter so much?
A vine you leave alone in summer grows like mad. Long trailing shoots, a dense canopy, bunches buried in shade. That costs you in three ways:
Less sweet, less ripe. Grapes need sun to build up sugars. If a bunch is hidden under the leaves, it stays sour and small.
More fungus. A dense, damp canopy dries slowly after rain or dew. That is exactly the climate powdery mildew and downy mildew thrive in (source: Groei & Bloei, Gardeners World). More air around the bunches means less fungus.
Wasted energy. Every shoot without a bunch and every surplus tendril costs the plant energy that is not going into your grapes.
Summer pruning solves all three. You take the brake off and steer the plant so the strength goes into the bunches and the sun can get in.
What are “laterals” on a grapevine?
Laterals are the side shoots that grow out of the leaf axils, so in the angle between a leaf and the main shoot. You will also hear them called side shoots, sub-laterals or water shoots. They do exactly what the Dutch name for them suggests, which is “thieves”: they steal sap and energy from the bunches (source: Groei & Bloei, directplant.nl).
You recognise them by their fast, floppy growth with no bunches on them. They shoot up incredibly quickly in summer and turn the plant into an impenetrable thicket within a few weeks if you let them.
How and when do you remove laterals?
You remove laterals with your fingers or with clean secateurs. As long as they are young and soft, you just pinch or snip them out.
A handy rule of thumb for how far to cut back:
- High up in the plant, near the bunches: remove the laterals completely. That is where you want light and air, not extra leaf.
- Lower down, away from the bunches: cut the laterals back to roughly one or two leaves instead of removing them altogether (source: directplant.nl, BetuweBomen.nl). Those leaves still pull their weight in photosynthesis without shading the bunches.
You do not remove laterals once, you do it all season. Go over the plant every two to three weeks (source: snoeien.info). Do it while they are young: then it is a quick pinch rather than sawing off thick shoots.
How do you thin a grapevine in summer?
Thinning is the second half of the job. Alongside the laterals, this is where you deal with the fruiting shoots, the bunches themselves and the leaves around them.
1. Limit the number of bunches per shoot
A shoot carrying too many bunches spreads its energy over too many grapes. The result: lots of small, moderately sweet bunches instead of a few good ones.
Rule of thumb: keep one to two bunches per fruiting shoot and take the rest off (source: Intratuin, Gardeners World, directplant.nl). If a shoot has more bunches on it, pick the best and fattest ones and snip the smaller ones away. On a young plant (the first few years) you can be stricter still, so the vine builds up strength first.
2. Pinch out the tips of the fruiting shoots
Pinching out means nipping off the growing tip of a shoot so it does not keep growing forever. That stops the plant making leaves and sends the energy into the bunch.
The rules of thumb differ a bit here, so watch the distinction:
- Fruiting shoot (with a bunch): leave a few leaves beyond the last bunch and then pinch out the tip. Some garden sources keep about two leaves past the last bunch (source: Gardeners World, directplant.nl).
- Shoot without a bunch: you can keep that one much shorter or remove it entirely. If you want to leave it for extra leaf, pinch it out at around five or six leaves (source: Intratuin, snoeien.info).
The leaves you leave close to the bunch feed the grapes. The leaves far beyond the bunch barely do, and they only take up room and light.
3. Take leaves away around the bunches
This is probably the most underrated job of the lot. Once the bunches form and start to colour up, take away the leaves that are shading them (source: Groei & Bloei, ELEO, BetuweBomen.nl).
Here is how to go about it:
- Only remove the leaves that genuinely put the bunch in shade, usually a handful of leaves on the sunny side.
- Do not strip the bunch bare: a bit of leaf protects against scorching in fierce sun.
- Do it gradually over a few weeks in late summer, so the grapes do not go from shade to full sun in one go.
More light means faster, more even ripening. More air means the bunches dry off quicker after rain, and that makes a huge difference to the risk of fungus.
4. Thinning the berries: optional but worth it
Berry thinning means thinning out the grapes inside a bunch, so the remaining ones grow bigger and the bunch sits looser. It is especially worthwhile on greenhouse vines and large bunches.
Do it while the berries are still small (around June to July, when the little stalks are clearly visible). With a fine pair of scissors, snip out the smallest, the innermost and the unpollinated berries. Reckon on taking off roughly half of them (source: Gardeners World, Intratuin). Sounds drastic, but what is left gets bigger, sweeter and less prone to rot because the berries are no longer squashing each other.
When and how often do you prune grapes in summer?
Summer pruning is not a one-off job, it is a rhythm. Here is a handy overview.
| Period | What you do |
|---|---|
| May / early June | Go over the first shoots. Take off shoots without bunches, pinch out laterals. |
| June | The main moment: reduce bunches to 1 or 2 per shoot, pinch out the fruiting shoots. Thin the berries if you want. |
| July to August | Remove laterals every 2 to 3 weeks, keep on top of new growth, keep the plant compact. |
| August to September | Gradually take leaves away around the ripening bunches for light and air. |
The common thread: go over your vine every two or three weeks and keep on top of it (source: snoeien.info). Small, regular rounds are far easier and far better for the plant than one big scalping.
What tools do you need?
You do not need much, but clean and sharp really does matter here.
- Sharp, clean secateurs for the thicker shoots. Sharp blades give a smooth cut that heals over quickly; blunt ones crush and damage.
- Fine scissors for thinning between the berries.
- Your fingers for young laterals and growing tips: you just pinch those out.
Disinfect your secateurs between plants and after any diseased spot, for example with methylated spirits or surgical spirit on the blades. Grapes are prone to fungal diseases, and dirty blades will carry them from one place to the next in no time. Prune on a dry day if you can, then the cuts dry off quickly and fungus gets less of a chance.
Preventing mildew with the right pruning
Grapes have two notorious enemies: powdery mildew and downy mildew. Pruning is your best preventive measure, well before you start thinking about sprays.
Powdery mildew shows up as a greyish, white powdery coating on leaves, shoots and berries. It thrives in warm, close weather with little air movement.
Downy mildew gives yellowish, oily patches on the top of the leaf with a white, downy coating underneath. It likes warm and wet.
What they have in common: both benefit from a dense, damp, poorly ventilated canopy. And that is exactly what you tackle with summer pruning. By removing laterals, thinning the leaves around the bunches and keeping the plant open, everything dries off faster and the fungus gets far less of a chance (source: Groei & Bloei, Gardeners World). Clear up fallen and infected leaves too, because that is where the fungus overwinters.
The difference between grapes in a greenhouse, on a wall or over a pergola
The pruning principles are the same everywhere: laterals off, pinch out, thin. But the conditions differ, and that calls for some nuance.
In a greenhouse. Here you have the most control over warmth and therefore the sweetest grapes, but also the biggest fungus risk because the air stands still. Be extra strict with thinning and open windows and doors for ventilation. Berry thinning pays off most in a greenhouse, because the bunches there often get full and large.
Against a wall. A warm south-facing wall works like a radiator and gives beautiful ripening. Tie the shoots in as a fan or horizontally against the trellis or wires, so the bunches hang well spread out and all catch sun. Keep the shoots growing away from the wall short.
Over a pergola or an arch. Lovely for shade and looks, but be warned: this is where the temptation to let the plant run riot is greatest. Right above your head is exactly where you miss laterals and surplus leaves. Make a point of going over it regularly, or before long the bunches will be hidden in a roof of leaves.
Common mistakes when summer pruning grapes
- Starting too late. Wait until the plant is a jungle and you end up cutting away thick shoots, losing far more energy than you needed to. Start in June and keep on top of it.
- Stripping everything in one go. Especially the leaves around the bunches: take it all off at once and the grapes will scorch in full sun. Do it gradually.
- Removing low laterals completely. Lower down the plant, the side shoots should actually stay at a leaf or two so they can help feed the vine.
- Leaving too many bunches on. More bunches is not more harvest, it is lots of small, sour grapes. Dare to be selective.
- Working with blunt or dirty secateurs. That crushes the shoots and spreads fungal disease. Sharp and clean, always.
- Mixing up winter and summer pruning. Hard cutting back to the buds belongs in winter, not in summer. In summer you prune green and light.
Frequently asked questions about summer pruning grapes
When should you prune grapes in summer?
Start in June, as soon as the little bunches are visible, and repeat every two to three weeks into late summer. The main job (reducing bunches and pinching out shoots) falls in June, and removing leaves around the bunches is something you do in August and September.
What are laterals on a grapevine?
Laterals are the side shoots that grow out of the leaf axils, also called side shoots or water shoots. They carry no bunches and steal energy from the plant. Up near the bunches you remove them completely, lower down you cut them back to a leaf or two.
How many bunches do you leave per shoot?
As a rule of thumb you keep one to two bunches per fruiting shoot. You snip the rest off, so the plant puts its energy into a few good bunches instead of lots of small ones.
Can you remove the leaves around grape bunches?
Yes, and it helps a great deal. In late summer, gradually take away the leaves shading the bunches so sun and air get in. Do not strip the bunches completely bare, because a bit of leaf prevents scorching.
Does pruning prevent mildew?
To a large extent, yes. Both powdery and downy mildew like a dense, damp canopy. By removing laterals and thinning out, you keep the plant open and dry and cut the risk of fungus considerably. Always clear up infected leaves.
Do you prune greenhouse grapes differently from outdoor ones?
The actions are the same, but in a greenhouse you are extra strict with thinning and ventilating because the fungus risk is higher when the air stands still. Outdoors, against a warm wall, the emphasis is more on tying in and spreading the shoots neatly.
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