How to select and plant hydrangeas

What are hydrangeas?

Hydrangeas are woody shrubs that produce large circular or conical clusters of flowers. They’re renowned for their versatility and come in an extensive colour palette that includes vibrant pinks, blues, purples and whites. They’re a great way to add colour to your garden, whether in a feature area or next to some fencing.

Hydrangeas are one of the few plants that can thrive and flower in the shade, which makes them a favourite with gardeners. These beauties are low-maintenance and don’t need much attention to produce their impressive, billowy blossoms. Hydrangea breeders have come up with new colours, sun-loving types and scaled-down varieties for pots, which means there’s bound to be a hydrangea that's right for you.

Types of hydrangeas

There are more than 75 species of hydrangea, with something to suit every gardening style. Among the most popular are the mophead or macrophylla hydrangeas, known for their large, globe-like clusters, growing up to a maximum height of around 2m.

If you’re looking for something drought-tolerant, oak leaf hydrangeas have a whimsical conical shape to their clusters and lush, green, oak leaf-shaped foliage. Hydrangeas also come in climbing varieties, which can be planted to creep across trellises or archways, giving height to your garden and adding that fairytale cottage feel.

Colour-changing flowers

Hydrangeas have a special party trick: they change colours, depending on the soil pH level. Hydrangea flowers naturally occur in a range of colours, with blue, pink and white being the primary hues. Blue hydrangeas typically emerge in acidic soil conditions (pH below 7), where aluminium availability increases. In contrast, pink hydrangeas thrive in alkaline soil (pH above 7), where aluminium availability decreases, resulting in pink petals. White hydrangeas stay white irrespective of soil pH due to the absence of aluminium and the presence of other compounds.

You can adjust your soil's acidity by incorporating coffee grounds, lawn clippings, and vegetable peelings. Adjusting the pH should be done prior to the formation of flower buds, typically in winter, as it can take a few months before any noticeable change occurs. If you don’t want to mess around with different colours, don’t worry – there are many varieties that have stable coloration and won’t change. 

How to grow hydrangeas

Soil

Hydrangeas thrive in moist, free-draining soil that’s rich in organic matter, no matter the pH. Before planting, be sure to add some compost and organic mulch to boost the soil quality and draining ability.

Hydrangeas can also thrive in clay soil, provided you’ve incorporated a good amount of gypsum and compost before planting. Mixing these into the clay will increase the drainage and keep the roots happy.

Sun

Hydrangeas need a good balance of sunlight and shade. They generally appreciate some morning sun, especially in cooler climates, and benefit from partial shade in the heat of the afternoon. It’s a good idea to plant them near a fence or tree (avoiding any tree roots), near larger plants or shrubs, or beneath pergolas. This dappled or filtered sunlight helps prevent the plants from wilting or drying out when it gets too hot. If you live in a hotter climate, you’ll get the best results by placing your hydrangeas in areas with more shade, protecting them from the intense midday sun. Some hydrangea varieties will tolerate full shade or even full sun, and understanding the sunlight preferences for your hydrangea variety will help ensure their wellbeing.

For more advice on growing hydrangeas...

Learn how to maintain healthy hydrangeas.