The easy pruning of hydrangeas in 10 steps

How do you prune hydrangeas? We are talking about bushes that are among the most loved and easy to grow, yet their thinning puts even green thumbs in crisis. In fact, when hydrangeas are badly pruned – this is their botanical name – they do not bloom. The operation is not complicated at all, but it is essential to act precisely. To clarify how to proceed, we asked for advice from Rita Paoliformer nursery specialist in the cultivation of these plants, as well as author of the recent manual Hydrangeas together with Alberta Ballati And Valeria Galgani (Edagricole 2022).

1. When is the right time to prune hydrangeas?

“We are waiting for the past risk of frosttherefore we cannot prune when temperatures are close to zero and not even when the climate is mild if there is a possibility that they can still occur late frosts, because sub-zero temperatures could damage the plant by penetrating the plant tissues through the cuts. In Southern Italy, therefore, one can already proceed with the pruning in Januarywhile in the Center it is good to wait i early February and in the North and in the mountains it is advisable to wait for the end of the month or even i early March“, explains the expert. Furthermore, in February, the buds are already well developed, so it is easy to distinguish between the swollen and rounded ones – which will certainly give flowers – and those with a more elongated shape, from which green branches will grow.

2. We divide the hydrangeas into two groups

Exist 180 species of hydrangea in nature, plus thousands of man-made varieties. Talking about pruning, however, can be simplified by dividing hydrangeas into two categories. “The first group includes the plants that flower starting from June on the old branches, i.e. those grown in the previous summer. The common “ball” hydrangeas belong to this first group, i.e. Hydrangea macrophyllabut also H. serratasmaller than the former, with thin branches and elongated leaves, and more H. aspera, with large velvety leaves. These are the hydrangeas to pay more attention to, because if we mistakenly eliminate the branches with the largest buds, the bushes do not bloom.

On the other hand, the second group includes the varieties that blossom from July on the new branches, those born in spring; among them, H. arborescens And H. paniculataable to flower even when they are drastically pruned”, explains Rita Paoli. It is therefore essential to keep the label with the name of the plant to understand which pruning team our hydrangea belongs. That said, if we have space to grow them, we can also decide never to prune them: “Unpruned hydrangeas live well just the same, but they give smaller and more numerous flowers”.

3. How to prune classic hydrangeas

For the varieties of the first group, including the hydrangeas more classic, to be grown in the shade or in partial shade, proceed as follows. “We grab i dried flowers with one hand and cut off the branch that supports them one or two centimeters above the pair of larger, round and well swollen buds. Then they eliminate half of the hair right from the hairline older, woody branches, recognizable by the wrinkled bark, to rejuvenate the bush by giving rise to new branches from the ground. You don’t touch the rest”, recommends the nurseryman.

4. How to deal with full sun hydrangeas

Among the hydrangeas of the second group, which bloom on new branches, there are the varieties of Hydrangea arborescenslike the famous ‘Annabelle’, which forms big white clouds in summer, or H. paniculata, with clusters of flowers in the shape of a conical panicle. These hydrangeas are also known as hydrangeas on their own, because they require one direct exposure to sunlight for at least half a day. “However they are pruned, these hydrangeas manage to flower. For strong plants, we remove any broken or visibly dry branches, then prune some of the older, brown branches, finally shorten all the other branches by cutting them off above the third or fourth pair of gems, counting them starting from the bottom”, says Paoli.

5. How to treat oakleaf hydrangea

The Hydrangea quercifolia, or oak-leaf hydrangeas, can be recognized as the name suggests by the leaves, they grow in the sun and produce large white panicles in summer. They are scenic plants that turn red in autumn and often keep their leaves until winter. “They have twisted branches with reddish bark, beautiful even in winter, so it’s better not to prune them; it’s enough to remove the dried flowers. If we have to limit their size, we cut off the branches that bother us to give the plant back shape at the end of winter”, he says the nurseryman. Also for climbing hydrangeas, such as H. petiolaristhe same rule applies: the less you touch the better, eliminating only the dry.

6. In June, we shorten the most “overbearing” branches

Speaking of classic hydrangeas, it often happens that in June, in the moment of full splendour, some new and very vigorous branches grow more than the others, overpowering the flowers, especially on moist and well-fertilised soils. “These shoots can be trimmed by bringing their height below that of the flowers, to give the plant a new shape”, assures the expert. “New plants can be reproduced from the pruned branches; we cut segments with two nodes (the points where the leaves attach), remove the lower pair of leaves and put the cutting in a good soil. Then we place the pot in the shade and we water every day”.

7. The summer remorse: the most useful of all

“Everyone regrets pruning hydrangeas when they are still beautiful, yet the pruning that is done in July and August is the most effective, the favorite of nurserymen because it ensures plants with a harmonious and compact shape, which certainly flower every year. Always in the light of summer moreover, this one is hotter and drier summer pruning reduces transpiration of the plant and prevents the bush from succumbing to heat strokes and lack of water”. We intervene when the inflorescences they have lost the bright colors, although they are still beautiful. “We cut all the flowering branches at the desired height, giving the plant a nice shape; there’s no need to worry about where and how, because the buds that will be born in September will still be able to give flowers the following year”, guarantees Rita Paoli. Cut flowers with summer pruning can be dried to keep them beautiful all year round, as explained below.

8. The trick for drying hydrangea flowers

The inflorescences are harvested at the end of flowering (from August to October), when they change color and their consistency is thicker to the touch, as explained in the Hydrangeas manual. The branch is cut, the leaves are removed leaves from the stem and hang the bouquets upside down in a dry and dark place for at least 20 days. Alternatively, we can enjoy these flowers indoors by placing them in a vase with 10 centimeters of water; when the liquid is completely absorbed, the hydrangeas will certainly be dried.

9. How to handle the greenhouse hydrangeas received as a gift

In winter and early spring, pots of hydrangeas made to flower in the greenhouse are increasingly being offered, as if they were a bouquet of flowers. A purchase with a high environmental impact that we obviously do not recommend, but it can happen that you receive one of these “forced” plants to blossom in the middle of winter as a gift. These greenhouse hydrangeas they must be treated as if they were houseplants until the beginning of spring, keeping them in a cool environment (about 18°C) and bright and watering them regularly. After flowering, we prune drastically leaving only 2 or 3 pairs of nodes on each branch, to encourage the plant to resume its natural cycle, so we keep the pot in a cool place. In spring, we repot, fertilize and place the plant outside in the shade.

10. How to form a hydrangea sapling

Plants are often found on sale tree-shaped hydrangea, but by their nature these plants will tend to branch out a lot and return to bushes. The exceptions are Hydrangea paniculate which manage to maintain the set shape and develop like small trees, up to 3-4 meters in height. If we want to give it a try, we buy an already well-formed plant and select the most robust and regular branch, at least one meter long. Therefore, always in winter after the frosts, we eliminate all the other branches. Then a bamboo rod is placed alongside the main stem, fixing it with an elastic tie. In spring, we only let the shoots grow at the top of the branch, eliminating those born further down. Within two years, pruning as explained for the hydrangeas of the second group, we will be able to have a perfect tree.