Training, Pruning and Thinning out Grapes
There are two reasons to prune grapes:
- To form the basic skeleton (important in the early years);
- To encourage the development of new shoots in spring.
Pruning is not really necessary until the vine is 3-4 years old.
When the vine has reached this age, select a few long, strong branches, preferably branches with lots of side branches. Tie these down to a pergola, wall, fence or other support.
It is important for these branches to have plenty of light and warmth, so a south-facing wall is best.
The branches that have not been tied down should be removed completely. The branches that have been tied down form the basic skeleton of the vine. These are the leaders, or main branches.
Cut all side branches growing from the leaders down to about 10 cm. Repeat this every year in winter.
The leaders will continue to produce grapes for years. However, as the vine grows older it is advisable to tie down a young branch from time to time to create a new leader that can replace an older leader. This rejuvenates the vine. When creating a leader, all fruit should be removed from this branch in the first year. This should also be done in the case of a leader that is allowed to grow longer, with all grapes being removed from the new section at first.
Grape vines should be pruned in winter. November and December are the best months, as the sap begins to rise in early spring and pruning during that period will cause the vine to bleed. Even so, this rarely bothers the plant, so if you have forgotten to prune in November-December this can still be done up to March.
Young shoots (side branches) develop on the vine in early summer. Summer pruning can begin as soon as the bunches of grapes begin to appear, cutting back branches bearing fruit to the third or fourth leaf from the bunch. If a side branch has more than one bunch, the bunch(es) farthest from the main branch should be removed.
As the vine continues to grow and create new shoots, summer pruning is continuous and should be carried out every two weeks during the growing season. Some of the leaves around the bunches can also be removed to allow more sun to get through. Do not remove too many leaves. The more northern the climate, the more leaves are needed to give the grapes their sweetness.
Thinning out refers to the practice of cutting a few grapes from each bunch. This used to be common practice for greenhouse vines, as this encourages the development of the remaining grapes, although it is not really necessary for vines grown outdoors.
However, we do recommend that you remove some bunches completely in August. The more bunches you remove, the sweeter and tastier the remaining grapes will be. Wait until the grapes have finished growing before doing this. Once the growth period has ended, the ripening period begins, during which time the grapes do not become any larger but their sugar content increases. In June/July the grapes are still growing. Thinning out too early will make the grapes watery rather than sweet.
If you want to cover your vines with netting to keep out the birds, attach the netting at the sides rather than throwing it over the plants. This is because most birds approach from the side or from the ground.