How to grow shrubby hydrangeas

Choosing a hydrangea

There are a number of different hydrangea types but they all enjoy similar growing conditions. They vary in size from small shrubs to sizeable, almost tree-like specimens so check the plant label when buying to get one that is suitable for your space.

Which hydrangea you choose will likely depend on your preferences for flower colour and/or shape.

Mophead and lacecap cultivars of Hydrangea macrophylla (and also Hydrangea involucrata and Hydrangea serrata) change colour depending on the acidity or alkalinity of the soil ( pH

This describes how acid or alkaline soil is, and is expressed as a number between 0 and 14. Soil with a pH of 7 is neutral, an acid soil has a lower value, and an alkaline soil has a higher one. Most plants grow best in soil that’s within a specific pH range, so it’s useful to know your soil’s pH. Testing kits are easy to use and widely available in garden centres and online. ) that affects aluminium availability. Those with blue or pink flowers tend to be blue in acid soils (high available aluminium levels), mauve in lightly acid to neutral soil

The acidity/alkalinity of soil is measured on a pH scale, which runs from 0 to 14. Soil classed as neutral has a pH between 6.5-7.0, even though a pH below 7 is still technically acid, because the widest choice of plants grow in this range. You can easily check your soil pH with a simple testing kit, widely available in garden centres or online. Many plants thrive in neutral soil, except those than need notably acid or alkaline conditions. conditions, and pink in alkaline conditions. White, red and green-flowered cultivars, remain white or green regardless of soil pH.

Different hydrangea species also have differently shaped flowers. For round flower heads, choose mophead cultivars of Hydrangea microphylla (hortensia) or Hydrangea arborescens. For flatter flowers select lacecap cultivars of Hydrangea microphylla,Hydrangea serrata, Hydrangea villosa or Hydrangea aspera. And, finally, for cone-shaped flowers go for Hydrangea paniculata or Hydrangea quercifolia.

If you want to see large plants before you buy, why not visit a garden with a hydrangea collection for inspiration.

Hydrangea Derby
Holehird gardens

Buying a shrubby hydrangea

The best choice of hydrangeas in garden centres is available from mid-summer when they are in flower, but containerised plants are available all year round.

Check the height on the label as some will grow into sizeable shrubs.
In garden centres they are usually sold in 3 litre pots at 30cm or more in height. Mail order plants may be sold as young cuttings

A method of growing new plants from parts of an existing plant, such as sections of root, stem, leaf or bud. When prepared correctly and planted in the right conditions, they can produce roots and eventually become independent plants. There is a wide range of different methods for taking cuttings, depending on the plant and time of year. in 9cm or 1 litre pots.

When to plant

Plant your shrubby hydrangea soon after purchase. The best time to plant is in spring or autumn. Containerised plants can be planted all year round as long as the soil is not frozen, too wet, or excessively dry in summer (but you can water them well if you really want to plant them then).

Soil preparation

Cultivars with blue flowers remain blue if they are growing in acidic soil ( pH

This describes how acid or alkaline soil is, and is expressed as a number between 0 and 14. Soil with a pH of 7 is neutral, an acid soil has a lower value, and an alkaline soil has a higher one. Most plants grow best in soil that’s within a specific pH range, so it’s useful to know your soil’s pH. Testing kits are easy to use and widely available in garden centres and online. 4.5-5). For more information on soil acidity see our guides on this and on how to acidify your soil.

Understanding and testing soil pH

Acidifying soil

Buy hydrangea colourant

Where the blue colouring proves unreliable (you are getting purple and pink shades), you can use ‘hydrangea blueing compounds’, which contain aluminium sulphate. Always follow the manufacturer’s instructions. If the soil is very alkaline, or if there are obvious pieces of chalk in the soil, this treatment will not work and planting in containers with peat-free ericaceous compost

Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. is the best option.

If you wish to enhance red or pink flowers, apply a dressing of ground limestone or chalk at a rate of 75-100g per sq m (2-3oz sq yd) in winter.

Hydrangeas thrive in evenly moist soil so after planting improve the planting area by mulching

Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. with organic matter, such as garden compost or a manure-based soil conditioner.

How to plant

• Water the plant well before planting
• Make your planting hole as deep as the rootball
  The roots and accompanying soil when a plant is removed from a container or lifted from the ground. and three times wider
• Plant your hydrangea so that the surface of the compost in the pot is level with the surrounding soil to avoid planting too deep
• Firm the soil around the rootball well by pressing with the heel of your boot/shoe
• Mulch
  Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. with a soil improver
  Any substance dug into the soil to improve its structure. This is usually organic matter, such as well-rotted manure, garden compost or leafmould, but could be an inert substance such as lime or gypsum. leaving, 10-15cm (4-6in) gap around the base, to reduce the drying out of the soil
• Water in to help establishment and aim to keep the soil damp in the coming weeks

Planting trees and shrubs

Where to plant

• Ideally, plant your shrubby hydrangea in light shade. However, you can plant in a sunnier spot if the soil is not too dry in summer
• Plant away from frost pockets or exposed spots to reduce late frost damage to the new spring growth
• Spacing will depend on the vigour of the chosen plants, ranging 90cm-2.4m (3-8ft). Check the plant label for eventual size

Hydrangeas in containers

• Grown more compact hydrangea cultivars, such as Hydrangea macrophylla ‘Red Hot Violet’ and ‘Altona’, in containers
• If you are gardening on alkaline soils and want to retain blue flowers, grow your hydrangeas in containers using ericaceous compost
• Otherwise use a mix of two parts of peat-free John Innes No.3 and one-part peat-free multipurpose compost

Container maintenance

Watering

• Water newly planted hydrangeas as needed during the first growing season
  The period of time when an individual plant is in active growth. This will depend on the local climate and light levels, and can vary between different plants, although it is broadly from spring to autumn. from spring to summer when we’ve had no significant rain for 7-10 days
• Even mature plants will benefit from watering during hot dry spells. To reduce moisture stress, regularly mulch
  Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. with organic matter, such as leafmould, garden compost
  Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. or a manure-based soil conditioner, to help the soil retain moisture

Mulches and mulching

• Check the moisture levels of containerised plants regularly and ensure they don’t dry out. Move containers to shadier spot in summer to reduce drying out
• Water blue-flowered cultivars preferably with rainwater to retain the flower colour but, if rainwater is in short supply, use tap water to prevent drought stress

Feeding

Regular feeding of established plants

Established plants have been in their current location for two or three years and so have well-developed root systems able to support strong growth with healthy foliage and flowers. is not generally needed. Too much fertiliser encourages excessive soft, leafy growth, with plants less likely to develop flower buds

A bud is a small, undeveloped shoot that contains the potential for new growth. Buds are typically found on stems, where they can be apical (found at the tip) or axillary (found between leaf axils) and may develop into leaves, shoots or flowers. and more at risk from frost damage.

Struggling shrubs growing on

Transferring young plants from one container to a slightly larger one, where they will have more room to grow and fresh potting compost. This encourages continuous, healthy growth. lighter, sandier soils may benefit of spring application of general fertiliser. Drought stress can also cause this problem so mulching

Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. may be more helpful.

Overwintering

Most hydrangeas are hardy throughout most of the UK, but the young buds may be susceptible to damage from late frosts. There is the option to move plants in containers to a more sheltered spot such as a cold greenhouse or against a sheltered, sunny wall to provide protection for the buds and new growth.

There is no need to wrap the pot, as this does not provide sufficient insulation to prevent the rootball

The roots and accompanying soil when a plant is removed from a container or lifted from the ground. freezing in an average winter.

You can place the pot on pot feet or a few bricks to improve drainage and so prevent waterlogging. In dry spells in winter, check that the compost does not dry out.

Deadheading mophead and lacecap hydrangeas (Hydrangea macrophylla)

• There is no need to immediately remove the faded flowers. The dead blooms can offer interest well into the winter and help protect the new tender growth below from frost damage
• Wait until mid-spring before cutting back the stems to the first or second strong healthy pair of buds
  A bud is a small, undeveloped shoot that contains the potential for new growth. Buds are typically found on stems, where they can be apical (found at the tip) or axillary (found between leaf axils) and may develop into leaves, shoots or flowers. down from the faded bloom
• If desired you can deadhead
  Deadheading is the process of removing spent flowers from plants to encourage more blooms and prevent seed production. This helps to redirect the plant's energy into producing more flowers rather than producing seeds. lacecaps after flowering, but mopheads should be deadheaded in milder areas only

Pruning established mopheads and lacecaps (Hydrangea macrophylla), and H. serrata

• Prune in mid-spring
• Prune lightly, but regularly. The flowers are formed on new shoots growing from the previous year’s stems, therefore heavy pruning will result in loss of flowers
• Cut out one or two of the oldest stems at the base to encourage growth of new, more floriferous replacement shoots
• Renovate overgrown or neglected shrubs by cutting off all the stems at the base. The new stems will not bloom until the following year

Pruning Hydrangea paniculata and H. arborescens

• Prune in early spring, before the shrubs start actively growing
• Regular pruning is not essential, but annual pruning of last year’s growth encourages more prolific and larger flowers
• Prune last year’s growth to the lowest pair of healthy buds, creating a low framework of woody branches. This usually results in a pruned framework of no more than 25cm (10in) high but, if more height is required, cut to about 60cm (2ft) tall
• Neglected plants generally respond well to harder pruning to restore the low framework

Pruning other hydrangea species

These include Hydrangea aspera, H. aspera Villosa Group, H. quercifolia and H. sargentiana

• Prune in spring
• Only minimal pruning is needed to remove dead and over-long stems

They are easily propagated from cuttings. The plants will take two to three years to start flowering.

Take softwood cuttings

Softwood cuttings are taken from spring to early summer (Apr-Jun), using material from the soft and flexible young shoot tips from this seasons growth, which root readily. Use for hardy and tender perennials, deciduous shrubs, climbers and some trees. from late spring to mid-summer, semi-ripe cuttings

A method of growing new plants from parts of an existing plant, such as sections of root, stem, leaf or bud. When prepared correctly and planted in the right conditions, they can produce roots and eventually become independent plants. There is a wide range of different methods for taking cuttings, depending on the plant and time of year. in mid-summer and or hardwood cuttings in winter.

Cuttings: softwood

Cuttings: semi-ripe

Cuttings: hardwood

Species hydrangeas can also be propagated from seed in spring.

Frost damage

New spring shoots are prone to frost damage. Prune back badly damaged shoots to just above the first undamaged pair of buds

A bud is a small, undeveloped shoot that contains the potential for new growth. Buds are typically found on stems, where they can be apical (found at the tip) or axillary (found between leaf axils) and may develop into leaves, shoots or flowers. on live, healthy wood.

Hydrangea scale

Most noticeable in early summer when stems and leaves are covered with white, waxy, flat ‘blobs’.

Hydrangea scale