Growing Hydrangeas

Brighten up a shady spot with these easy-care shrubs for long-lasting colour from spring to autumn

Growing Hydrangeas

Hydrangeas create a colourful garden border and make a striking cut flower. Image: Getty Images 

They may make you think of your gran but she was onto a good thing with hydrangeas. Not only can they be grown just about anywhere in Australia they also flower prolifically in blue, pink, red or white. 

Hydrangea macrophyllais the most widely recognised species. The mophead type has big round flower clusters while lacecaps feature long, flathead open blooms with bud-like flowers in the centre. 

Older varieties tend to be larger, while the newer are smaller, with an extended flowering time and brighter colours. There are also miniature types that get to about 300mm high.

Anthony Curnow of Plants Management Australia says that hydrangeas are simple to plant but need nutrients to thrive.

Says Anthony, ‘Make sure you dig plenty of organic matter into the soil. Be aware that, depending on what you add and the soil type, the colour of the hydrangea may change over time.’ 

Colour change

It’s true that Hydrangea macrophyllaflowers can change colour, depending on the acidity of the soil. More acid soils give blue flowers, alkaline soils red or pink and neutral purple, while white stays white regardless of soil pH.

Anthony says it’s best to accept the colour you have but to change the blooms, add lime to the soil for pink flowers or aluminium sulphate for blue. 

You need to change the soil pH before the flower buds form so it’s best to treat the soil after August. 

Prune for health

The only common mistake in growing hydrangeas is not pruning them. 

‘Many gardeners typically don’t prune their plants,’ says Anthony. 

‘Which means that they will continue to grow but due to the amount of competition between each branch for nutrient and water, the flower size can sometimes be smaller than if you do prune.’

Anthony says to wait until after flowering to prune your plants. 

‘You’ll notice the buds beneath flowers begin to shoot. Prune back the plants to about seven buds below the flowerhead, or lower if you would like to keep your plants slightly shorter. 

‘Another thing you’ll notice is new shoots without flowerheads coming from towards the base of the plant.

‘These shoots are those that will flower first the following year, so be sure not to prune these back or you’ll remove any chance of flowers.’

In the garden

Here’s a complete guide to growing healthy hydrangeas at home. 

POSITION hydrangeas in a location with semi-shade. They prefer moist conditions but tolerate full sun in cool areas and some do well in full shade. 

Protect plants from northerly winds and strong afternoon sun, as this can burn the leaves and flowers. 

Hydrangeas grow well in most free-draining soils but benefit from the addition of well-rotted compost, dug through before planting.

PLANT by digging a hole twice as wide and only as deep as the container the hydrangea came in. 

Remove the plant from the container and gently tease out any parts of the rootball to encourage the root system to grow out into the soil in which it’s being planted. 

Fill in the base of the hole enough for the soil level to match the area surrounding the new planting.

CARE for plants with deep watering once a week in warm weather. 

Apply a liquid fertiliser containing seaweed emulsion during the growing season or slow-release granules in June. 

Mulch with well-rotted animal manure or sugar cane mulch to protect their fibrous roots, which grow close to the soil surface. 

‘They’re excellent at telling you when they need a drink, as their large leaves fall and become limp as a result of thirst,’ says Anthony. 

WATCH FOR the occasional caterpillar attack in spring and summer, and pick them off by hand. 

Powdery mildew can be a real problem in hot humid conditions and for plants with erratic watering. To prevent it, water regularly at soil level.

For small amounts, just remove infected leaves. Spray infestations with fungicide at the recommended rate, or a mix of one part milk to
10 parts water every 10 days.  

PROPAGATE by snipping off softwood cuttings, the new growth, in spring. Remove most of the foliage but keep about two to four of the top leaves. 

Dip the cut end of the softwood cuttings in rooting hormone and plant in a damp propagating mix. 

After about five months they should have developed roots and can be planted into the garden in a spot with semi-shade. Or grow in a pot for a season in a protected sunny spot.

Choosing a variety 

Hydrangeas are hardy shrubs native to southern and eastern Asia. There are more than 100 species of deciduous and evergreen plants in the genus. TIP Grow them in containers if space is an issue but use a nutrient-rich mix. 


Macrophylla 

Also called florist’s hydrangea or bigleaf, this deciduous species has big shiny leaves and its mophead and lacecap flowers mainly bloom on old wood. The blooms are often left to dry on the plant and cut for use as a long-lasting dried flower. 

macrophylla plant, handyman magazine,
This deciduous species has big shiny leaves and its mophead and lacecap flowers mainly bloom on old wood. Image: Getty Images

Arborescens

A deciduous shrub called smooth hydrangea, it has deep green leaves and flat cream-coloured flowerheads in summer. It blooms on new wood, so can be pruned hard. The blossom colour isn’t altered by soil pH, but the flowers go pale green as they age. 
 

arboscens, handyman magazine,
Arborescens looms on new wood, so can be pruned hard. Image: Getty Images 

Quercifolia

The commonly named oakleaf hydrangea displays autumn colour on both foliage and old flowers and is an easy-to-grow shrub that blooms even in deep shade. It flowers on old wood but isn’t as sensitive to frost as other varieties.

quercifolia, handyman magazine,
The commonly named oakleaf hydrangea displays autumn colour on both foliage and old flowers. Image: Getty Images 
 

This article originally appeared in the April 2013 issue of Australian Handyman magazine 

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