All about Hydrangeas
Hydrangea are easy to grow and need only minimal pruning which makes them a low maintenance shrub. They are also not so fussy about soil types and conditions and some, particularly the climbing Hydrangea, will even grow in shade. Generally speaking most Hydrangea are large shrubs from 1.5m - 3m (3-10ft) and so need a fair amount of growing space.
Hydrangea make great border plants and are grown for their lovely showy flower heads, predominately flowering pink, mauve, blue , cream and white. Hydrangea are (mainly) deciduous and a summer flowering shrub which require little maintenance, and will grow in most soils including chalk, with a preference for sun but Hydrangea will also tolerate partial shade. In some varieties the flower colour can be affected and changed by the pH of the soil; which is whether the soil is acid or alkaline. Growing in an acid soil the Hydrangea flowers blue and in alkaline pink; the white flowers are unaffected. Hydrangea are a woodland plant with a preference for moist but well drained soil in sun or semi shade. As a woodland plant, they are best planted with some shade and avoiding the full afternoon sun as Hydrangea will thrive in the cooler part of the garden. As always, it is a question of the right plant right place, which means avoid planting where there is hot afternoon sun or cold easterly winds. Generally Hydrangea is tolerant of most growing conditions.
There is a very attractive climbing form of Hydrangea, H. petiorlaris will tolerate a higher degree of shade and can be useful to grow up a shady wall. This really is a lovely climber, relatively fast growing and so tending to be vigorous but beautiful flowers and I have seen grown to great effect on a large semi shaded wall where it can be left to grow unchecked and form a mass of white flowers in the spring. It is self supporting but does need a reasonably large space.
There are also some varieties of Hydrangea which have scented blooms, such as Hydrangea paniculata 'Wim's Red' and also some compact varieties H. panciulata Little lime ('Jane') and Hydrangea with beautiful delicate colours such as pink turning to white as in Hydrangea paniculata Vanille Fraise ('Renhy')
Hydrangea macrophylla come in two forms: 'Lacecaps' see illustrated below a lovely delicate bloom, and 'Hortensias (mop head ) with rounder flower heads.
When selecting a Hydrangea for the garden many grow to around 3m, such as H.Paniculata 'Unique', Serrata the popular ''Blue bird' smaller around 1.2m and there are many Macrophylla varieties around 1.5m. a useful size for most gardens.
Pruning is not essential to Hydrangea, both Mopheads and Lacecaps will flower without pruning. The benefit of pruning is to keep the shrub in shape and pruning can improve flowering.
The time for pruning Hydrangea, with the exception of the climbing Hydrangea H.Petiolaris, ( see below,) Hydrangea should be pruned in later winter or early spring.
With Mopheads, if you garden in a cold or exposed area, there is benefit in terms of frost protection to leave the flower head over winter. In early spring remove the old flowers pruning down to a pair of strong healthy buds. Sometimes in spring, if there is a bad frost, it can damage the new growth, cut back further to a pair of healthy buds. Also remove any spindly weak stems and on older plants remove a few, 2/3 older stems from the based which will encourage new growth later in the spring.
Lacecaps this type of Hydrangea needs a light prune in February remove the top of the stems with last season's flower head in place and cut down to just above a green bud which will be showing by now. Do not prune harder, or lower, to do so is a mistake which can prevent the Hydrangea flowering later in the summer.
To prune the climbing Hydrangea this should be immediately after flowering to restrict it's growth cutting back long shoots. It can be pruned harder if needed, but if you are pruning hard it is best to stagger over more than one year because if it is pruned hard all at once, there maybe significantly less flowers the next year.
Hydrangea paniculata and H. arborescens need more attentive pruning, (which maybe why they are less popular) each spring prune back to a framework which means cutting back stems to a pair of buds. These varieties flower best if pruned harder so can be cut back to the lowest pair of buds which may result in the plant, post pruning, only being 25cms but you can of course leave several buds on and prune less hard.
This image shows how to prune Lacecap and Mophead Hydrangea. In early Spring cut off the flower heads as illustrated. Should a frost stike and damage the new growth prune again as shown. Periodically you can thin out and cut back the old growth from the based of the shrub to promote new growth
Types of Hydrangea
This is Hydrangea Paniculata which needs some pruning and flowers best if regularly pruned in the spring. It flowers in the late summer producing white or cream flowers.
Prune as detailed above to maintain flowers otherwise Hydrangea is usually trouble and disease free but comes with a size warning - they can grow quite large up to 7 meters and 5 meters wide,
Hydrangea Petiolaris the climbing hydrangea
The climbing hydrangea Petiolaris is vigorous, which means fast growing and needs plenty of space. The image left shows how easily it covers most of a wall which means you need a big space for this and it will reward you with fantastic fresh green foliage in spring, ( it is deciduous) and lovely delicate flowers in early summer . If you need to cover a large wall, particularly if it is partially shady, this is a great choice and it can be contained, to some extent, by hard pruning.
As it is summer flowering, hydrangea Petiolaris should be pruned after it has flowered as it produces flowers on the current year’s growth. A vigorous, deciduous climber which is fully hardy and self clinging.
The common Hydrangea which group is divided into two groups: Lacecaps and the Mopheads. Some varieties of Hydrangea Serra are also described as lacecaps. It is very confusing buy and plant what you like.
Image is Hydrangea macrophylla 'merveille browning' Prune in the spring cutting down to flower buds.
Hydrangea Macrophylla Hortensias is also known as mophead. All Macrophylla are affected
by the PH of the soil acid soils produce blue flowers alkaline pink.
To be precise, a Ph of less than 5.5 produces blue flowers, more than 5.5 pink.
The fading blooms of Hydrangeas are very attractive and last for weeks. Left is Hydrangea Paniculata where the limey white blooms are fading through pink to pale white.