Hydrangeas usually grow into shrubs with multiple stems, however, one hydrangea type, the Hydrangea paniculata, can be pruned to grow like a single-trunk tree.
The tree hydrangea starts blooming in mid-summer, producing a spectacular display of blooms, making them one of the most popular landscape plants.
If you’ve gotten yourself a hydrangea tree from a nursery, the care recommendations I’ve summed up below will help you successfully grow an impressive tree hydrangea.
Size & Growth
Before planting outside, it’s important to have all the necessary information of the size the hydrangea tree can reach maturity.
The average size hydrangea trees reach maturity is somewhere between 8 to 15 feet in height and 8 feet wide. Some Hydrangea paniculatas, like the Hydrangea paniculata ‘Grandiflora’ or Pee Gee, can even grow to become 25 feet tall.
You can grow this hydrangea as a shrub or, with pruning, you can grow it as a tree. Usually, nurseries will already prune them into a tree-like shape when the plant is still young.
Otherwise, you’ll need to remove side shoots as they appear or any suckering shoots at the base to train the hydrangea to grow as a tree.
Paniculatas enjoy full sun to partial shade. Local climate can be helpful in deciding whether a hydrangea needs more sun exposure or more shade.
In cooler climates, the hydrangea tree does best with more sun exposure, while in warmer climates partial shade is better.
Ideally, they should receive at least 4 hours of full sun per day. Blooms tend to last longer if they’re not exposed to the hottest sun during the day.
Hydrangeas of all types enjoy moist to medium-moist soil. You should never allow the soil to go completely dry, otherwise the foliage will start drooping and wilting.
While in spring and mid-summer, your hydrangea may naturally receive adequate water if there is enough precipitation, in summer and during summer heatwaves, it’s crucial that you irrigate the soil.
It’s best to water hydrangeas with a hose and to water deeply only at the root level, so that no water reaches the leaves.
When water sits too long on the leaves, it can promote fungal and bacterial diseases, so it’s best to water early in the morning, so the leaves have a chance to dry until night.
Hydrangeas enjoy slightly acidic soil, although the paniculata will grow even in alkaline soil as long as it’s high in organic matter and drains well.
It’s important to ensure proper drainage, otherwise the roots of your hydrangeas will sit in water and start to rot.
Therefore, if you have areas in your garden that naturally drain better, favor these instead of locations where water tends to pool and drain with difficulty.
Temperature & Humidity
You can grow the hydrangea paniculata in hardiness zones 3 to 8. They are cold hardy compared to other varieties. They do great with average humidity and benefit from shade in warm climates.
Hydrangeas don’t require much in the way of fertilizing. Adding fertilizer once in early spring and once after blooms fade in fall is all they need. Adding compost to the soil during summer will also benefit the hydrangea tree.
Fertilizers for hydrangeas can have different formulations and different dosage recommendations. Some weaker solutions may need application every 2 weeks.
To avoid fertilizer burn and associated plant damage, make sure to follow dosage recommendations exactly as prescribed by the label of the fertilizer.
Potting & Repotting
Because of its tall growth, the Hydrangea paniculata isn’t suitable for growing in a pot. If you want to grow a hydrangea in a pot, try Hydrangea macrophylla or the Mountain hydrangea.
As potted hydrangeas grow, they need to be transferred to a large planter to accommodate the roots, and make sure the pot doesn’t dry out too fast.
If you’re planting a hydrangea in your garden that comes from a nursery or a greenhouse, make sure it’s a variety that’s cold-hardy in your area.
Plant hydrangea trees in spring when there is no chance of a late frost destroying delicate green growths or buds.
In the first two years, your hydrangea tree may require some extra bracing or support until the main stem is strong enough.
The extra support will help it grow upwards and also prevent the plant from falling over in case of strong winds.
How to Propagate?
The hydrangea tree is easily propagated from cuttings. Cuttings should be harvested in spring when new growths appear.
Choose cuttings that are around 3-5 inches long and feature at least 3 leaf nodes. To root the cuttings, plant them in a moist potting medium that contains peat moss and perlite.
Make sure that at least two of the leaf nodes are covered by the potting medium. You should keep the cuttings out of direct sunlight, in bright indirect light. Keep the soil moist and in about 4-6 weeks, the cuttings will form roots.
After a couple of more weeks, after the roots get strong enough, you can plant the cuttings outside in your garden.
If your aim is to grow the paniculata as a tree, you’ll need to choose a main stem, stake it in place, then remove any competing shoots that emerge from the trunk.
You can grow any hydrangea paniculata variety as a tree. I mentioned how the ‘Grandiflora’ (or Pee Gee variety) is the tallest-growing one, but there are smaller varieties too.
The smallest-growing one is the Hydrangea paniculata ‘Bobo’ that stays at around 3 feet tall, followed by the ‘Limelight’ and ‘Big Ben’ varieties that grow to about 6-8 feet tall, and lastly the ‘Pinky-Winky’ variety that grows to 8 feet tall by 8 feet wide.
Regardless of the hydrangea tree variety, the care requirements are generally the same — full sun to semi-shade, moist to medium-moist soil, and good drainage.
The paniculata hydrangea can be grown both as a shrub and as a tree, although if you want to keep it as a tree, it needs a bit of pruning.