When to prune grape vines – expert advice to get the ‘critical’ timing right

Pruning grape vines is an important part of growing these perennial climbing plants, and keeping them healthy and productive year-after-year.

Grapes love warmth and sunshine and can be grown either outdoors or indoors. Where you grow grape vines will be dependent on your climate, and this will play a part in when to prune them.

It is important to understand when - as well as how to prune grape vines - as there are potential implications to pruning at the wrong time. This includes a reduced yield, an increased risk of damage or disease, and a lower overall quality of fruit.

The best times to prune grape vines

The best time to trim grape vines is during their dormancy period, as pruning while the vines are growing can cause them to bleed sap, which will stress the plant.

Grapes that are grown in a backyard greenhouse will start actively growing earlier in the year than those outdoors as part of kitchen garden or vegetable garden. Grapes are popular outdoor crops in warmer areas to grow on walls, or up a pergola, as well as being good plants to grow in a greenhouse in colder climates. For example, in a walled garden I ran in the UK, the grape vines I looked after grew happily in a greenhouse, but would not have thrived outdoors.

Always clean and sharpen tools before and after doing any pruning. Using dirty or blunt tools is a pruning mistake that, like trimming at the wrong time, has the potential to damage the health of plants and spread diseases. 

We hear from gardening experts about the best times to head out with pruning shears and give your grape vines a trim.

Winter pruning

If you are growing grapes outdoors, they can be pruned through winter and early spring, when they are fully dormant during the colder months. The common months for pruning is from January through to March. You ideally want to time the pruning just before the buds are set to break, so the most appropriate time may be dependent on your local climate.

Stefano Watson, from Avio Vineyards and Winery, recommends that pruning is done ‘after the last hard freeze’, which he does in around mid-February in Northern California. 

He adds: ‘Timing is critical; pruning too early can lead to issues like die-back from freezing or the entry of diseases. It's essential to prune when the sap starts to flow, allowing the vine to naturally seal the wound.’ 

This window for pruning is smaller when grapes are growing indoors in a greenhouse; it starts in winter and only runs for a small amount of time. For many indoor grape growers, late November through December is the best time to prune grape vines.

‘Early January is the last chance to prune grape vines before growth starts again,’ says Ruth Hayes, a fruit growing expert and gardening writer. ‘This is the last chance to prune grapevines before they start back to growth. If left any longer, they will start to bleed sap.’

Ruth Hayes

Ruth is horticulturally trained, with a qualification from the Royal Horticultural Society. She writes regularly for Homes and Gardens and was gardening editor of Amateur Gardening magazine. Her work involved matching gardening tasks with each season.

Summer pruning

Some grape growers lightly prune their vines in summer to remove excess growth that has occurred during the season. This needs to be done carefully and can be useful to control the density of the canopy, promote the ripening of fruit, and help to control diseases, including fungal issues like downy and powdery mildew.

Stefano Watson says: ‘Thinning is a practice that reduces the crop load on the vine, preventing excessive fruit production. Leafing, which involves reducing the number of leaves on the vine, also enhances air circulation and sunlight exposure for the crop.’

Thinning shoots is best done in early summer when they are smaller. Removing leaves can be done throughout summer and the fruits will then benefit from the increased amount of sunshine that can penetrate into the centre of the canopy.

Only prune these fast growing flowering vines lightly during the growing period, as fresh pruning cuts during warmer and more humid periods can leave vines increasingly susceptible to diseases. Being too heavy-handed with summer pruning can also reduce the production of fruit and affect your eventual yield of grapes.

Stefano Watson

Stefano Watson is the owner of Avio Vineyards in Sutter Creek, California. He currently cultivates 30 acres of grapes and has over two decades of experience in growing wine grapes.

FAQs

If you want to add these great climbing plants to your garden, then you do need to be able to provide them the warmth they enjoy. A great option is to grow muscadine grapes, a type native to the southern US that perform well in zones 7-10. There are many varieties of muscadine grapes, of which some are self-fertile and capable of pollinating themselves - making them a great option for small backyards.