planting & care
Feeding and fertilising
Mulch hydrangeas every year in spring, with leaf mould, well-rotted manure or compost. They don’t need feeding, as this encourages leafy growth at the expense of flowers.
Changing the flower colour of hydrangeas
You can change the colour of the flowers on lacecap and mophead hydrangeas and Hydrangea serrata from pink to blue by feeding with a fertiliser low in phosphorous and high in potassium. You can also grow your plant in a pot of peat-free ericaceous compost and water with rain water to keep the flowers blue. Changing hydrangea flowers from blue to pink is trickier. You will need to raise the pH by adding dolomitic lime.
Hydrangeas do best in moist soil and have a tendency to wilt in hot weather, so keep well watered during hot spells.
Lacecap, Mophead & Serratta.
Prune in mid-spring. They produce their flowers on old wood, so don’t prune them back hard, or this summer’s flowers would be lost. Traditionally, the old flowers are left on over winter as it protects the new growth beneath. Cut back the flower head to just above the top set of plump buds that are forming under the dead flower head. This is where the new flowers will form. If you have an overgrown plant, cut some of the stems off at the base.
paniculatA & aborescens
Cut back in early spring. Pruning is not essential, but left unpruned the plant will get taller with most of the flowers at the top. These two types of hydrangea produce flowers on new wood, which means that you can cut them back harder without losing this year’s flowers. Prune last year’s growth back to a healthy framework that’s between 30cm and 60cm high, depending on how tall you want your plant to be. Prune to just above a pair of healthy buds on each stem.
With older plants severe pruning may be needed to remove old, worn-out growths, or branches growing over windows or protruding outwards from the face of the building. Likewise, hard pruning maybe required where maintenance needs to be carried out on the structure supporting the plant. Drastically shortening back long branches, removing sections of older stems to just above a strong young branch or growth shoot lower down, or cutting completely back to a main branch, or even to ground level may be necessary. The end result should be a skeleton frame work of reasonably well-spaced branches.