Tree hydrangea (Hydrangea paniculata) is a quick-growing upright shrub with a coarse texture. Unlike more bushy hydrangeas, these plants provide later summer blooms when few other bushes are in bloom. They are popular landscape plants for massing or grouping in mixed shrub borders or woodland gardens. They also work well as specimen plants or in hedges. The natural habit is a shrub with multiple stems, but tree hydrangeas are sometimes pruned to look like trees. Taller forms are sometimes planted by community park boards as boulevard plants in place of taller trees.
These easy-to-grow bushes are well-suited to USDA hardiness zones 3 to 8. This is one of the most winter-hardy of all the hydrangeas, and it has excellent tolerance for polluted urban environments.
This shrub typically grows eight to 15 feet tall, although some forms may grow as tall as 25 feet. The plant has oval, dark-green leaves and blooms from mid-summer to fall with sharply pointed flower clusters that are six to nine inches long. The large, cone-shaped flower heads (or "panicles") are widest where they meet the stem and taper down from there. The white "blooms" are actually mainly sterile sepals (petal-like plant parts). As such, they last much longer than true blooms. The flower heads take on a pinkish color over time before fading to tan or brown for the winter.
|Botanical Name||Hydrangea paniculata|
|Common Name||tree hydrangea, panicle hydrangea, peegee hydrangea|
|Plant Type||deciduous shrub or small tree|
|Mature Size||8 to 15 feet tall; 8 feet across|
|Sun Exposure||full sun to part shade|
|Soil Type||organically rich, medium-moisture, well-drained soils|
|Soil pH||tolerates a wide range of soils, from acidic to alkaline, although slightly acid soil is best|
|Bloom Time||July to September|
|Flower Color||white, pink|
|Hardiness Zones||3 to 8|
|Native Area||eastern and southern China, Japan, Sakhalin|
How to Grow Tree Hydrangea
Grow Hydrangea paniculata in medium-moisture, well-drained soil that is rich in organic material. Choose a full-sun to part-shade location. This plant can be trained as a small tree by judicious pruning but achieves its best form if grown as a large shrub with multiple stems. The best form is achieved by keeping it in the six to ten-foot range.
To train as a tree, choose a main shoot and secure it to a sturdy stake. Prune away other shoots, and remove any side shoots on the main stem up to a level about three-fourths of the total shrub height. Continuously check for suckering shoots around the base of the plant, and keep them trimmed away.
Bloom occurs on current season’s growth (new wood), so prune as needed in late winter to early spring. Frequent pruning is necessary to keep the plant shaped correctly, and it may require two or more years before the true tree shape is accomplished. When grown in shrub form, larger flower clusters are achieved if you thin the plants down to five to ten primary shoots.
Feed the plant twice a year, once in early spring (immediately after pruning is a good time) then again just after it finishes blooming.
Tree hydrangea grows well in full sun to part shade. These plants require more sunlight than standard hydrangeas. In warmer climates, some shade can be advantageous.
The best soil will have medium moisture, good drainage, and be high in organic material. Any pH level will suffice, but a slightly acidic soil is ideal.
Soil needs to be consistently moist to prevent wilting.
Temperature and Humidity
Tree hydrangea tolerates a wide range of temperatures. It is more cold-hardy than most hydrangeas but may benefit from some shade in hotter climates.
Feed tree hydrangeas twice a year, in early spring and in fall, immediately after flowers have faded. During summer, application of compost is all the feeding that is necessary.
Varieties of Tree Hydrangea
- Hydrangea paniculata Grandiflora grows to 25 feet with a 10-foot spread. Flowers are pure white.
- H. paniculata Limelight grows six to eight feet tall and five to seven feet wide and has a greenish color in its flowers.
- H. paniculata Big Ben grows six to eight feet tall and five to seven feet wide and is valued for having flowers of a deeper pink color.
- H. paniculata Bobo is a dwarf type, growing only about three feet tall and wide.
- 'H. paniculata Pinky Winky grows to a maximum height and width of eight feet and is known for its bicolored flower heads (pink on the bottom, white on the top).
Rigorous pruning is necessary only if the plant is to be trained as a tree. This is done by selecting a main stem, staking it in place, then systematically removing competing ground stems and shoots emerging from the "trunk" of the tree.
On shrub forms of the plant, the size and vigor of blooming can be increased by cutting away all but five to ten main shoots.
Pruning should be done before spring growth begins, or after flowering is completed for the season. Untimely pruning may remove the new wood from which flower shoots emerge.
Tree hydrangeas have almost no serious insect or disease problems. There is some slight susceptibility to bud blight, bacterial wilt, leaf spot, rust, and mildew. Aphids and mites sometimes appear on the plants.