How to Grow and Care for Hydrangeas?

The Hydrangea is a classic flowering shrub, with lush glossy foliage and dense blooms of colourful, delicate flowers.This beautiful deciduous perennial will make a fantastic addition to any Summer garden. 

Hydrangeas are easily one of our favourite flowering shrubs here at Diacos, and they’re highly popular with our customers at this time of the year. That’s why we’ve put together a comprehensive guide to help you grow and care for these stunning plants. 

You can also check out our Quick Guide to Hydrangeas to view this information in a shorter format, or learn how to Make Your Own Hydrangea Wreath for the Christmas holidays 

Planting a Hydrangea

Hydrangeas are flowering shrubs native to Asia and The Americas. This hardy plant will continue to grow and blossom for many years when kept in the right conditions. Some of the most popular varieties include the common Mophead, the Lacecap and the Evergreen.

Hydrangeas have developed a reputation as popular summer plants, with their exotic blooms bursting into life from late November through to early February. However, these durable shrubs can actually be planted in your garden at almost any time of the year, except during the peak of a harsh winter.

The best time to plant is usually in late Spring or early Summer, just in time for the flowering season to begin. Planting towards the end of Autumn, when conditions are mild, can also yield good results if the plant is mature enough to withstand the colder weather.  

Lightly break up your soil first for extra drainage, before planting the roots to around the same depth as the pot they came in. Water your plant in well if the conditions are dry. Otherwise, a good soaking of Spring rain should get the job done nicely.

Soil and Drainage

We recommend preparing your soil before planting your Hydrangeas. This will help to create the best possible conditions for those stunning seasonal blooms to arrive.

These shrubs will need a rich and fertile environment in order to flower successfully. A well-aerated, loamy soil mixed with around 10% organic matter (like humus or compost) will create an ideal environment for your shrub to produce flowers.

For dense clay soils, try adding Gypsum to help break up the dirt and improve aeration. If your soil is sandy, adding Peat Moss or Mushroom Compost can help to absorb more moisture. The aim is to try and strike the right balance between allowing moisture to drain while still letting the plant absorb enough water to survive.

Adding a good quality Slow-Release Fertiliser after planting can also help to increase the nutrient levels in your soil. It’s a good idea to fertilise annually at the beginning of Spring. This is one hungry shrub, and the top-up of nutrients will help it to produce better flowers. Avoid nitrogen-heavy fertilisers, as they tend to encourage more foliage growth instead.

Watering

It’s all in the name – ‘Hydra’. These lush green plants love a drink of water, and they can become especially thirsty in the dry summer heat. Generally, a Hydrangea should be watered every few days, though this may differ slightly depending on your soil quality.

As mentioned earlier, drainage is one of the most important factors for creating a large healthy bloom. While this shrub does require a moderate to high level of watering, it’s still possible to overwater your plant if the moisture has nowhere to go. Moist soil is ideal, but soaking wet soil will contribute to poor blooms and create an environment for rot and fungus.

If you find that your soil is staying wet for a long time, reduce your watering frequency immediately and try to improve drainage. On the other hand, you may find yourself watering frequently but struggling to maintain moisture levels in the heat. In this case, adding a layer of Mulch will help to retain that moisture longer and reduce the time you spend watering.

Sunlight

Placement is another very important factor when caring for these plants. Ideally, you want to find somewhere with good sun exposure in the morning and filtered shade in the afternoons. 

This dappled shade will help to protect your flowers from drying out too much during the harsher summer temperatures. Bigleaf varieties like the Evergreen Hydrangea (Dichroa Versicolor) are even more tolerant of partial shade conditions, making them ideal for those tough shady spots like corners, fencelines or tree-canopy areas.

One other thing to consider when choosing a position is providing suitable airflow, and not just so you can watch them sway gently in the breeze! While strong winds may damage the brittle stems, the occasional light wind blowing through will stop moisture from collecting in the dense flowerheads and help to prevent potential rot and fungus buildup.

Hydrangeas can change colour.

Hydrangea flowers are well known for their peculiar ability to change colour. This is especially common with popular Mophead varieties and the intricate Lacecap flower.

This colour change certainly isn’t a random occurrence. In fact, it’s got everything to do with the acidity (pH level) of your soil. This means that it’s something you can easily control by adding popular garden additives. It’s important to note that when altering your soil, pH levels will change gradually – you won’t see a difference overnight .

Adding Garden Lime will lower the acidity of your soil by raising the pH level of your garden beds. Meanwhile, decomposing compost and mulch will naturally start to lower pH and increase acidity. Adding small amounts of coffee grounds or even sulphur are also popular ways to increase acidity.

For blue flowers, aim for acidic soil with a pH level of below 5.5. Meanwhile, pink flowers will grow in more alkaline soils with a pH of 5.5 or over. White and purple flowers are typically unaffected by any acidic changes.

Pruning and Maintenance

Light pruning is necessary to keep your shrub well maintained, and it will encourage new flower growth for the next season. Though many people may feel hesitant to give flowering plants the chop, removing the dead flowers when summer is over will help the plant to redistribute important resources towards the new shoots.

When removing the dead flowers, look for a pair of buds located on the stem. You want to make the cut around 5cm above these for the best chance of promoting new growth. When doing a late Summer prune, try not to remove more than 30% of the plant at any given time, otherwise you may risk sending it into shock.

It’s also important that you don’t touch any new shoots that are coming up from the base of the plant. These will become the start of next year’s bloom, and pruning them early may cause the flowers to bloom sporadically or even stop them from flowering at all.

Some parts of the foliage will start to wilt and die off in late winter as the plant recovers from the dormant season. This is a good time to prune your plant back a little bit harder, removing any leaves that look like they are dying, diseased or otherwise gangly and unproductive.

Pest & Disease Control

Unfortunately, the foliage of Hydrangeas are susceptible to common garden pests. These include Aphids, Scale insects (which can be identified by clusters of small white eggs) and Slugs. All of these infestations can be easily removed with common pesticides.

Other common issues include rot, fungus and powdery mildew, all of which can arise from this shrub’s shady location and the potential for overwatering. Remove and dispose of any leaves that appear to be infected and apply a good quality fungicide to the shrub. Fungicides are formulated to kill diseases quickly without causing any serious harm to your plant.

Propagation

Another great thing about Hydrangeas is that they are very easy to propagate from cuttings. In the Summer, soft tips or stem cuttings of around 5-10 cm can be used for propagation. In the Winter months, you can use 10 cm cuttings of hardened wood instead.

In all of these cases, propagation is as simple as dipping your cutting in Rooting Hormone or cutting gel and placing it in a pot of Propagating Mix. Keep it moist and well sheltered in a full shade position. In 2-4 weeks, your cutting should start to take root.

You’ll know that rooting has begun when the plant resists being gently tugged on. New leaf growth should also begin to appear. At this stage, your shrub is ready to be transported to a larger pot and moved to a filtered shade location.

This has been our comprehensive guide to growing and caring for Hydrangeas. When the right conditions are met, this gorgeous and easy-to-care for shrub will bloom year after year, bringing colour and happiness to your garden.

If you’ve got further questions about growing Hydrangeas, feel free to ask our friendly and knowledgeable team. Our Diacos staff are expert gardeners who are happy to help you solve any gardening issues. We also provide advice & quotes for planning and landscaping.