When it comes to pruning hydrangeas, many amateur gardeners are unsure because different pruning rules apply to different types of hydrangea. Here we explain what to look out for and how to make the shrubs bloom magnificently.
Hydrangeas are easy to care for and flower for a very long time – what’s more, their inflorescences are still attractive even when withered. No wonder, then, that hydrangeas are among the most popular garden plants and can be found in almost every garden. When it comes to pruning hydrangeas, however, many amateur gardeners are unsure – for good reason, because hydrangeas are pruned to different degrees depending on the species they belong to. If you prune incorrectly, the flowers may not bloom the following year. The plants are therefore divided into two pruning groups.
Pruning hydrangeas: The most important at a glance
- Pruning for all hydrangeas is at the end of February
- Only remove old blossoms and frost-bitten shoots from farmers’ hydrangeas
- Always cut just above the first pair of green buds
- For panicle and ball hydrangeas, prune old flower shoots to one or two bud pairs
- If the shrubs are very dense, cut out individual old shoots completely
Hydrangeas of cutting group 1
The plants of cutting group 1 include all varieties of the farmer’s hydrangea (Hydrangea macrophylla) and the plate hydrangea (Hydrangea serrata) as well as the giant leaf hydrangea (Hydrangea aspera ‘Macrophylla’), the velvet hydrangea (Hydrangea sargentiana), the oak leaf hydrangea (Hydrangea quercifolia) and the climbing hydrangea (Hydrangea petiolaris). All these hydrangea species have one thing in common: they lay the new shoots for the next year, including the terminal flower buds, already in the previous year. If you carefully open a bud of the farmer’s hydrangea in autumn, you can already see the new inflorescence and the new leaves inside.
This means that hydrangeas in pruning group 1 should be cut back only slightly to protect the new shoots. As a rule, remove the old inflorescence just above the first intact pair of buds and, if necessary, thin out the entire plant a little more by cutting off the oldest shoots at ground level. You can, of course, prune the hydrangeas mentioned more in spring, but then you will have to do without the beautiful flowers for a year.
When should hydrangeas be pruned?
The best time to prune hydrangeas in pruning group 1 is early spring. Most hydrangea species in this pruning group are somewhat sensitive to frost. Therefore, remove all the shoots that froze in winter along with the old inflorescences. Here too, all shoots should be cut off at the height of the first healthy buds. Tip: If you are not sure whether a shoot of your hydrangea is frostbitten or still alive, you should simply scrape off a little of the bark with your thumbnail. If bright green tissue appears underneath, then the shoot is still intact. The bark tissue of dead shoots is usually already somewhat dried up and has a yellow-green hue.
Special case Hydrangea “Endless Summer”
From a botanical point of view, the hydrangea ‘Endless Summer’ is very close to the classic farmers’ hydrangeas, but it has a special characteristic: heavily cut back flowering branches from the previous year sprout again and, unlike the normal farmers’ hydrangeas, still bear flowers in the same year. This is why you can cut back the blue ‘Endless Summer’ and the white ‘The Bride’, which comes from the same breeding line, as much as you like in spring. In principle, however, you should only remove the faded flower heads from these varieties, otherwise the new flowers will start relatively late.
Tip: If you remove the first flush of flowers in summer immediately after the hydrangea has faded, the plants will form new flowers on the shoots. It is therefore worthwhile, as with the more frequently flowering roses, to reach for the pruning shears every now and then in summer.
Hydrangeas of cutting group 2
Pruning group 2 includes all hydrangeas that form their flower buds on the new shoots only in the year of flowering. This includes only two species: the snowball hydrangea (Hydrangea arborescens) and the panicle hydrangea (Hydrangea paniculata), including all varieties. Hydrangeas in pruning group 2 are pruned like classic summer bloomers: in late autumn or spring, simply prune all the shoots that have emerged in the previous season to short stubs, each with a pair of eyes. In the coming season, the remaining eyes will sprout vigorously and long new shoots with large terminal flowers will emerge.
With this pruning technique, the number of shoots doubles year after year, as two new shoots emerge from each old one. If the crowns become too dense over time, you should therefore remove weaker or unfavourably placed shoots or individual “twig brooms” completely.
Important: Do not cut back these plants too late, otherwise flowering will also start relatively late. You should have pruned the shrubs by the end of February. In sheltered locations, it is also possible to prune much earlier – for example, in late autumn – because the plants are more frost-hardy than hydrangeas in pruning group 1.
Officially, hydrangeas are classified as slightly poisonous, and contact allergies in the form of skin irritation can occur in particularly sensitive people during care work. If you know that your skin is sensitive to contact with plants, it is better to wear gloves for all care work on hydrangeas.