Pruning Hydrangeas

Pruning Hydrangeas
All you need to know about Hydrangeas.
There are 5 main types of Hydrangeas. Hydrangea macrophylla, paniculata, arborescens, quercifolia & petiolaris. The most popular Hydrangeas are macrophylla, paniculata & serrata.
  • Hydrangea macrophylla are divided into 3 types: mopheads, lacecaps & mountain hybrids. Mophead hydrangeas are the most popular with flower heads of blue, pink or purple. The flower colour depends on soil conditions. Lacecaps are identical to mopheads in every way except for the shape of the flowers. The little buds in the centre of a lacecap flower are fertile flowers whilst the larger flowers around the outer edge are sterile flowers. Hydrangea macrophylla serrata (Mountain hydrangea) is the least common variety. It produces much smaller flowers but is extremely hardy & can survive very harsh winters & harsh climates.
  • Hydrangea paniculata (Panicle Hydrangea)- are known for their large cone-shaped flowers. The flowers usually start white & might turn shades of pink. This variety is a taller grower & can grow into a tree. Hydrangea paniculata ‘Grandiflora’ grows best in cooler temperatures. They are very hardy. They are good for all year round interest with flowers from midsummer until the end of the year then attractive dried flower.
  • Hydrangea arborescens (Smooth or wild Hydrangea) – Grows well in both warm & cold climates. The most well known is Hydrangea arborescens ‘Annabelle’ which produces attractive large white flower heads that age to green. It is a most showy Hydrangea, the flowers can grow up to 30 cm (1’) across & grow whiter as summer progresses. It looks like a mophead variety. It is hardy & will tolerate cold conditions.
  • Hydrangea quercifolia (Oakleaf Hydrangea) – Very attractive foliage with leaves shaped like those of an oak tree that change to wonderful shades of orange, red & mahogany in autumn. Will tolerate light shade but is much better planted in sun & must have hot sun to flower well. It doesn’t grow well in soil that is permanently moist.
  • Hydrangea petiolaris (Climbing Hydrangea) – A unique Hydrangea as it can climb up structures & it has large flowers.
The Hydrangea arborescens varieties are much hardier than the ‘macrophylla’ varieties.  The ‘lacecaps’ & ‘mopheads’ require little maintenance as you only need to cut off the dead flowerheads in spring cutting down to a pair of buds. Hydrangea paniculata varieties add wonderful late summer & autumn interest only coming into flower in summer. Their flowers last well into autumn & then turn brown with a paper-like texture. They can be left on the plant for added interest in the winter garden or cut off & used in the house. These plants require the least maintenance only needing to be pruned back around March. Hydrangea paniculata ‘Limelight’ produces the most abundant flowers with a profusion of conical white flowerheads tinged with green that slowly age to reddish-pink.
Hydrangea quercifolia are actually the easiest shrubs to grow provided that they are planted in well-drained soil with a little shade in hot weather.
 Hydrangea seemanii is one of the petiolaris group. It is an evergreen with sweet smelling flowers towards the end of spring/beginning of summer.& climbs like a vine. It can grow up trees without damaging the tree or cover up unsightly walls.
The more recently introduced ‘Endless Summer’ series of Hydrangeas are repeat flowering.
Planting – Dig a hole a little bigger than the root ball then plant at the same depth as the plant was in the pot. They need fertile, well-drained  soil  with plenty of moisture. Add well-rotted manure or compost when planting. This will ensure that you grow a strong, healthy plant. If the plant is overwatered or planted in soil that is too wet the leaves will turn yellow. If the leaves look dry & start to go brown more water is needed.
Growing conditions –Think carefully about where you want to plant a Hydrangea & check out the best growing conditions required for each variety. Hydrangea macrophylla varieties prefer early morning sun & shade in the afternoon. Some varietiesof Hydrangea do well in less or more sun. The macrophylla varieties will produce fewer flowers if grown in too much shade. Some Hydrangeas will wilt if planted in direct sunlight for the whole of the day.
Pruning – Most varieties of Hydrangea don’t need to be cut back every year, except the Hydrangea  paniculata varieties.  The plant will still flower but the volume & appearance of the flowers won’t be as good as if it had been pruned. Pruning reduces the number of resources a plant needs. More energy & nutrients are available for the plant. This increased energy goes into the remaining growth causing flowers to look fuller, larger & more beautiful. Dead wood can be cut out at any time of year. Some varieties flower on both old & new wood, other varieties flower on either new or old wood. Most plants should be pruned even if only occasionally as pruning encourages new growth & improves health. Most varieties of Hydrangea are deciduous & look dead all winter.
Hydrangea quercifolia only ever needs a light prune as it flowers on the old wood. If you want to prune it hard back do so immediately after flowering. Hydrangea macrophylla varieties do not require pruning but are  grow best if deadheaded. Deadheading  triggers the plant to put energy into the root & new flower growth instead of producing seed.
 Hydrangea paniculata varieties do require pruning every year to ensure that they produce their magnificent conical flowerheads. In spring, around March, cut out any weak, spindly stems & any damaged or dead stems. Prune the remaining strong stems back to just above 2 buds from the base. If you don’t do this the plant will not produce the beautiful large flowerheads. Instead it will produce lots of small flowerheads. If you prune it as required the following year it will again produce large, stunning flowers.
All varieties of Hydrangea can be cut back to ground level & will still grow again. The flowers grow from buds which remain on the plant all year. The buds start to grow very soon after the current year’s flowers shrivel. If you want to cut out some stems do this immediately after flowering before the new buds form. This will ensure that you don’t cut off next year’s flowers.
Deciduous Hydrangeas can be cut back to ground level to reduce the plant if it is getting too big but next year’s flowers will not be as large. Old growth should be cut back after the flowers begin to go brown. Any very old stems should be cut off at ground level.
Be aware that after pruning the newer stems will not be as strong & so they will be more susceptible to wind damage or trampling so if you live in a windy spot some protection might be best.
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