If you are interested in keeping other parts of the hydrangea to grow as one or more additional bushes, remove as much dirt from the plant’s root ball as possible. The key is to expose the roots and base of the plant so you know where to make the cuts. Make sure the sides of your tree are well supported by good roots so you have a better chance of survival and success.
Best Types of Tree Hydrangea
There are different types of tree hydrangeas:
- Hydrangea paniculata ‘Grandiflora’ grows to 25 feet with a 10-foot spread and has pure white flowers.
- Hydrangea paniculata ‘Limelight’ grows 6 to 8 feet tall and 5 to 7 feet wide and has a greenish color in its flowers.
- Hydrangea paniculata ‘Big Ben’ grows 6 to 8 feet tall and 5 to 7 feet wide and is valued for having flowers of a deeper pink color.
- Hydrangea paniculata ‘Bobo’ is a dwarf variety, growing only about 3 feet tall and wide.
- Hydrangea paniculata ‘Pinky Winky’ grows to a maximum height and width of 8 feet and is known for its bicolor flower heads (pink on the bottom, white on the top).
- Vanilla Strawberry: 7-10 feet tall
Pruning
With clever pruning, this plant can be trained into a small tree. However, it is at its best when grown as a large shrub with multiple stems. Flowering occurs during the growth of the current season (new wood). So, prune as needed between late winter and early spring. Pruning too early may result in the loss of some flowers that growing season. When kept in shrub form, the shrub will produce larger flower clusters if thinned out to five to ten main stems.
To teach a plant to grow like a tree, choose a main stem and attach it to a sturdy stake. Trim competing ground stems. Remove any buds protruding from the main stem until the stem is about three-quarters of the way above the ground. Keep looking for buds around the base of the plant and remove them as they appear. Your main trunk keeps growing and has leaves on top so it looks like a tree trunk. It may take two years or more to achieve the correct tree shape.
Propagating Tree Hydrangea
Tree hydrangeas can be propagated by cuttings. The best time to do this is in spring or early summer, before the plants start to bloom. Cuttings are not only an inexpensive way to grow more plants, but they also allow you to grow more of your favorite tree hydrangea variety.
- Select a healthy stem that has not yet bloomed, and use sharp sterile pruners to snip a section about 6 inches long.
- Remove the leaves below the cuttings and cut the other leaves in half lengthwise.
- Dip the cuttings in rooting hormone and immediately plant them in small containers filled with vermiculite, coarse sand, or a combination of both.
- Water the cuttings, making sure the soil is moist but not too wet. Place a plastic bag or dome over the container to keep moisture in. Be careful not to let the plastic touch the cutout.
- Place the container where it receives bright but indirect light. Keep the soil slightly moist, but not soggy. Expect the cutting to take about a month to develop a root system. Then it can be transplanted.
How to Grow a Hydrangea Tree from Seed
Although it is possible to grow hydrangeas from seeds, keep in mind that this can be difficult to do. Therefore, most gardeners choose to propagate by cuttings.
If you decide to propagate by seed, allow a few flowers to develop on the plant. After a few months, the flowers are harvested in paper bags. This gives them time to dry. Store the flower heads in the bag for another week to ensure they dry out. Then shake the bag well. This will separate the tiny seeds from the flower heads. Keep in mind that these seeds are about the size of a grain of salt or pepper, so they can be difficult to find.
You can sow the seeds directly into the ground in the fall, or let them survive the winter and start sowing indoors in early spring. Fill the container with potting soil, then spread the seeds over the surface. Do not cover them with soil. Keep the soil slightly moist. Place the container in full sun and expect the seeds to germinate within a few weeks.
Potted and Repotted Tree Hydrangeas
Container-grown hydrangeas may need to be repotted every two years as they grow, depending on the size of the pot. The best time to repot a hydrangea is spring, when the plants are no longer dormant but not yet stressed by the summer heat. You can also repot the hydrangea in winter to give it more time to adapt to the new environment.
Choose a container that is a few inches larger than the previous container. The best container material is unglazed clay, which allows excess soil moisture to evaporate through the container walls. If it is the first time to pot tree hydrangea, please choose a flower pot with a diameter of 20 to 30 cm. The best growing medium is compost mixed well with a fertilizer suitable for hydrangeas. When planting, cover the roots and stems with soil. Place the container in the shade for the first few days, then gradually expose it to more sunlight to allow the plant to acclimatize to light and humidity. Keep the soil moist but not soggy.
To help the plant survive the winter, keep the soil moist until it freezes. Cover the roots with 3 to 4 inches of mulch, making sure to remove it after the temperature warms.
Light
Paniculatas enjoy full sun and part shade. Your local climate helps determine whether your hydrangea needs more sun or more shade.
In cooler climates, hydrangea trees grow best in more sun, while in warmer climates they do better in partial shade.
Ideally, they should receive at least 4 hours of full sun each day. Buds tend to last longer when not exposed to the hottest sun during the day.
Water
All kinds of hydrangeas prefer moist to moderately moist soil. Never let the soil dry out completely, or the leaves will droop and wilt.
While your hydrangeas will naturally get plenty of moisture during spring and summer when rainfall is good, it’s important to keep your soil watered during summer and summer heat waves.
The best way to water hydrangeas is with a hose and only water the roots so the water doesn’t reach the leaves.
If water sits on the leaves for too long, it can promote fungal and bacterial diseases. Therefore, it is best to water in the morning and let the leaves dry until evening.
Soil
Hydrangeas prefer slightly acidic soil, although hydrangeas will grow in alkaline soils as long as they are rich in organic matter and well-drained.
It is very important to provide good drainage, otherwise the roots of the hydrangea will get stuck in the water and start to rot.
Temperature humidity
You can grow hydrangeas in hardiness zones 3 through 8. Compared with other breeds, they are very vigorous. They grow well in average humidity and benefit from shade in warm climates.
Fertilizers
Hydrangeas don’t need much fertilization. Fertilize once in early spring and once after flowers fade in autumn. Adding compost to the soil in summer is also good for hydrangea trees.
Hydrangea fertilizers can come in different formulations with different dosage recommendations. Some weaker solutions may need to be applied every two weeks.
To avoid fertilizer burn and associated crop damage, be sure to follow the dosage.