Hydrangea trees can add a stunning vertical element to a garden – discover how to train and trim one with tips from a hydrangea expert

Hydrangea trees are shrubs trained and trimmed to look like a tree. They bring a vertical element to any space with their large, showy blooms atop tall stems, and can be underplanted with smaller shrubs or flowers.

They may sound potentially daunting, but hydrangea trees are simple to maintain. If you have experience with growing hydrangeas, you can have success with shrubs trained in tree form as the planting, watering, and feeding requirements remain the same.

Pruning and training are the ways they differ from regular shrubs, particularly if you want to train a shrub into a hydrangea tree rather than buy a pre-formed hydrangea tree. I spoke to a leading hydrangea expert about how to prune and care for hydrangea trees, plus what types of hydrangea are best suited to being grown in this unique way.

What is a hydrangea tree?

The term hydrangea tree may be misleading. It is not a special hydrangea variety that grows as a tree but describes a hydrangea shrub that has been trained to grow and take on the form of a tree. These types of hydrangea have their much-loved large flowers sitting on top of single trunks and strong side stems to give a tree-like appearance.

You will find that all types of hydrangea trees are formed from flowering shrubs in the panicle (Hydrangea paniculata) species. This is because panicle hydrangeas cope best with being grown in a tree-like form, with strong central stems and side shoots. It is common to see hydrangea varieties such as 'Limelight', 'Firelight', and 'Quickfire' sold as standard hydrangea trees in garden centers, nurseries, and online.

Lorraine Ballato, author of Success with Hydrangeas, claims the benefit of hydrangea trees being panicles is that ‘they are foolproof’ and easy to maintain, as well as their strong stems. But can other types of hydrangeas be grown as a hydrangea tree?

‘You could do this with other hydrangea species, but the side stem strength is the key issue. It must be able to hold up the flowers without breaking the stem,’ adds the hydrangea expert.

On why you should consider growing a tree type when landscaping with hydrangeas, Lorraine adds: ‘Tree hydrangeas are useful in a garden design as they contribute a vertical element plus you can underplant them either with other hydrangeas, annuals, or perennials, for season-long color.’

The easiest way to add a hydrangea tree to your backyard ideas is to plant hydrangeas that have been trained and trimmed to grow as a standard. If you have patience, you could shape an existing shrub into a hydrangea tree - but it will take several years to get that tree form.

Shop types of hydrangea tree

How to prune a hydrangea tree

Attempting to train and trim a young hydrangea to grow as a hydrangea tree means several years of training and hydrangea pruning. But it is possible and the result is a glorious full-sized standard specimen.

Let’s first look at this method of hydrangea tree pruning. To get started, Lorraine Ballato recommends: ‘Choose the stem that looks strongest and straightest to make that your trunk. Cut all other stems that are growing from the base.

The new trunk will require a sturdy stake to keep it upright and straight. Regularly remove any emerging growth from the lower three-quarters of the central trunk with clean and sharp pruning shears for the first two years.

Lorraine Ballato then says it comes time to ‘work on the top of the plant’. She adds: ‘This encourages it to produce new stems/growth that you can further trim into an umbrella-like form.’

Prune the main leader once it reaches at least 36 inches from the ground to promote branching and that tree-like growth habit. You can choose any height you want to fit your garden. From the following spring onwards, pruning the hydrangea annually will encourage new wood to grow that will carry that year’s flowers.

‘You do have to work to keep that umbrella-like shape each year when you prune in the spring,’ adds Lorraine. ‘I like to think of them as lollipops. Since this plant flowers on new growth, even hard pruning won't discourage it.’

Established hydrangea trees will need pruning in early spring to remove last year’s blooms and maintain the compact rounded shape at the top of the stem. This keeps the overall size and prevents the issue of too much weight once the shrub is in full bloom. Also, continue to remove side shoots that grow in the crown and on the trunk.

Lorraine Ballato

Lorraine Ballato is a hydrangea expert and the the author of the international best selling book 'Success with Hydrangeas', available at Amazon. She is also an in-demand speaker throughout the US and the resident hydrangea expert at the New York Botanical Garden.

How to care for a hydrangea tree

The maintenance requirements for a hydrangea tree are the same as for growing any shrub form. This includes planting them in partial shade, where they get protection from the sun in warmer climates, and a fertile, well-draining soil type.

Keep the soil consistently moist, but not waterlogged, and fertilize hydrangeas twice a year with slow-release feeds - once in spring and again in summer.

‘Fertilizing is important as you want to ensure solid, healthy growth, even though you will cut off many stems,’ says Lorraine Ballato. ‘That will simply stimulate the plant to produce more.’

Mulching annually will help retain moisture in the soil and can be a useful way to protect the roots from freezing temperatures and help winterize hydrangeas in colder climates.

FAQs

What is the best month to plant a hydrangea tree?

The ideal times to plant a hydrangea tree are in fall or spring, as the weather is mild and the ground moist at this time of year. The best time to plant container-grown hydrangeas is in spring once the danger of frost has passed, which ranges from February to May depending on your US hardiness zone. Alternatively, plant them in the fall, after the peak of the summer heat and well before the first frost.

How big do hydrangea trees get?

It will depend on the type of hydrangea, but hydrangea trees can reach 15-25 feet tall. However, most hydrangea trees are trained and trimmed to grow between six and ten feet.

When growing hydrangeas, you want as many of those glorious large flowers as possible. It can be a headache to see hydrangea flowers turning brown prematurely and ruining the display.

There can be several reasons why this may happen. It is usually a case of hydrangeas not getting enough water but browning blooms can also be caused by too much heat or sunlight.

This is one reason why hydrangeas prefer partial shade, as the flower petals can get damaged by too much intense sunlight.