Everything You Need to Know About Hydrangeas

AlanGardenMaster
Published on August 22nd 2020
180
Hydrangea lace-cap flowers
Hydrangeas are wonderfully easy to grow and have plenty of variety. They're the focus of a lot of plant breeding and selection and a common part of many gardens.
In this article, I'll go through some of the more common varieties and everything you need to know to grow Hydrangeas successfully!
Woman is cutting a bouquet of flowers hydrangeas with hedge clippers

Mop-Headed

Perhaps the most widely grown and familiar Hydrangea, the mop-headed is also called 'Hortensia'.
These grow to between 1.2-1.8 m height, but can reach almost 3m when sheltered or under trees.
Although the leaves are large and lush looking, it is the blooms that make this kind of Hydrangeas so popular. These appear in mid-summer and last well into the autumn.
Most varieties have pink or red blooms, but on lime-free soils, some produce flowers that are vibrant blue or purple.
Other varieties will produce white blooms perfect for lightening up shady areas.
The blooms are made up of sterile florets (the showy petals) and smaller, fertile flowers.
This attracts insects without the costs of creating large, showy and fertile flowers.
A large purple Hydrangea flower in a garden

Lacecap

Just like the mop-headed Hydrangea, the lacecap is easy to please, will grow to a similar size and lose their leaves in winter.
The key thing that distinguishes these apart is that lacecaps only have sterile florets around the perimeter of each bloom, so are arguably more subtle and less attention-grabbing!
Hydrangea White Wave flower

Arborescens and paniculata

Unlike most Hydrangea, these flower on the new wood (this year's growth), and although the colour range is restricted to white, they are fabulous garden plants!
Annabelle, an arborescens type, is extremely popular because of its football-size cream blooms.
Limelight, a paniculata type, is almost as popular, with a greenish hue to the cone-shaped blooms.
Hydrangea arborescens Vanille Fraise flowers

Aspera and oak-leaf

Less widely planted, these varieties of Hydrangea aspera, distinguished by their felt-like leaves are underrated in my opinion.
Hydrangea aspera Villosa Group is a favourite of mine and is excellent for planting close to a shady wall. Requiring little to no pruning, this plant will be covered with lilac lacecap blooms throughout the second half of summer without fail.
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Roy Lancaster with Hydrangea aspera Villosa
World-famous plant authority Roy Lancaster in my garden with Hydrangea villosa.
Oak-leaf hydrangeas produce white, cream or sometimes pink-tinged ice cream cone-shaped blooms. They get their name from their unusual leaf shapes, which often have vibrant autumn colours before falling in autumn.
Hydrangea quercifolia Harmony

Serrata

If your garden is small, then Hydrangea serrata could be for you. These plants rarely exceed one metre in height and are often narrower than they are tall.
Most have lacecap-like blooms with a good choice of blue, pink, red and white shades. However, 'Preziosa' is a perfect mop-headed form that changes colour as summer progresses. The blooms start as a soft pink and gradually darken through to a deep brick red.

Climbing

Climbing Hydrangeas are beneficial garden plants and relish the shade. They are self-clinging and need no elaborate trellis or wires for support. They produce aerial roots in the same way that ivy does and will have no trouble steadily climbing to the top of a two-story building.
Hydrangea anomala ssp. petiolaris is the most common, but I've taken a shine to a variegated form called 'Miranda'. This is just becoming more widely available here in the UK and may require a bit more sunshine than its parent. However, that's just my suspicion!
Climbing Hydrangea anomala ssp. Petiolaris

Growing conditions

Hydrangeas love rich soils! This includes soils with a high organic matter content, so will happily take all the garden compost that you can put under their branches.
Some are prone to late frosts, which can burn the soft new leaves as they emerge in spring. Plants usually recover quickly, but it's a reminder not to plant this shrub where late frosts are likely.

Moisture

Hydrangeas relish cool places in the garden where the soil is moist. Moisture can be aided by adding copious amounts of organic matter like root mulch. Best applied in winter, a mulch will retain moisture through to summer.

Shade

These plants like shade but, dry shade is to be avoided. Shade from deciduous trees or buildings is perfect.
Hydrangea Annabelle in shade

Coastal planting

Being remarkably salt and wind tolerant, you will often see Hydrangeas planted near the coast.
Hydrangea bushes

Blue blooms

With blue roses and blue orchids all the rage, blue flowers seem to be all we want at the moment.
Hydrangeas, unlike other plants, offer the real deal, rather than some un-naturally doctored blue. The key lies in having slightly acidic soil with a pH below 6.5. This allows the plant to take up more of the naturally occurring aluminium in the ground.
Not all varieties will produce blue blooms in acidic soil, so you'll need to check before buying.
You can help create the right conditions by watering on a proprietary blueing agent - or colourant.
Alternatively, you can throw a handful of rusty nails or other ferrous metal in the bottom of the planting hole. This is a cheap way to increase soil acidity and encourage blue blooms.
Hydrangea blue flowers

Pruning

Hydrangea arborescens and paniculata varieties need a hard prune in winter. This is because they flower on current season's wood. So cut them back to the main stem or the basic branch framework.
By contrast, the aspera, climbers and oak-leaf varieties need minimal pruning and just a bit of reshaping.
However, the majority of the others - mop-headed, lacecap and serrata - need to be pruned very lightly and only when winter is over. Just remove last year's dead flowers and a few inches of the stem by cutting just above a pair of fat buds. It helps if you also wholly remove weak and very old shoots.
dead hydrangea

Propagation

There are two main ways to multiply your plants. Softwood and hardwood cuttings are the best ways, and softwood is by far the best.
They are quick and easy to root and do not need sophisticated equipment. Hydrangea will rot on a bright windowsill.

Forced pot plants

You might wonder about Hydrangeas as houseplants. Started outside and then forced with heat in a greenhouse, these are often less hardy than garden varieties.
Hydrangea pot plants

Pests and diseases

Remarkably few pests and diseases attack Hydrangea species. Occasionally greenfly (aphids) might need to be controlled, and powdery mildew might be a problem if inappropriate growing conditions stress plants.

Drying

As if their performance in the garden were not enough, Hydrangeas have one final card to play! The flowers dry well and make long-lasting blooms for indoor winter displays.

Some popular Hydrangea plants:

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