How to Grow Hydrangea (Saxifragaceae) and Key Precautions

Hydrangea, also known as grass hydrangea or shade hydrangea, is a deciduous subshrub in the family Saxifragaceae. Native to southern China, it is a famous ornamental flower in the Yangtze River basin and regions to the south, and also makes an excellent potted flower in northern regions. So how do you grow hydrangea well? What precautions should you take?

How do you grow hydrangea well?

1. Soil

In early spring, rooted hydrangea seedlings from cuttings can be transplanted into pots. For potting, it is best to use a growing medium mixed from 4 parts leaf mold, 3 parts garden soil, 2 parts river sand and 1 part cake fertilizer; or a mixture of 4 parts compost soil, 5 parts sandy soil and 1 part cake fertilizer; or a mixed soil of 6 parts leaf mold, 3 parts sandy soil (or cinder) and 1 part cake fertilizer. After potting, water thoroughly and keep indoors for care, then move outdoors in early May. Hydrangea should be repotted once every 1 to 2 years in early spring, replacing the medium with fresh growing soil. When repotting, remove some of the old soil and rotten roots, and prune as part of the repotting.

2. Fertilizing

Hydrangea loves fertilizer. During the growing period, apply a diluted cake fertilizer solution about once every 15 days. To keep the potting soil consistently acidic, add 0.2% ferrous sulfate when applying liquid fertilizer, turning it into alum fertilizer water for irrigation. During the bud stage, apply 1 to 2 additional doses of 0.5% superphosphate soaking solution to promote larger, more colorful flowers.

3. Watering

Hydrangea leaves are relatively large and thick, so the plant needs a lot of water. In spring and summer, water frequently to keep the potting soil moist; during the high temperatures of midsummer, water once in the morning and once in the evening, and provide appropriate shade; in winter, water less, just keeping the potting soil humid; during the growing period, water thoroughly enough to keep the potting soil consistently moist, especially in summer, when ample water must be provided. From May to August, in addition to meeting the soil's water needs, spray the leaves once a day. However, hydrangea has fleshy roots, so do not overwater; too much water easily causes root rot. After September, as the weather gradually cools, gradually reduce watering so the branches grow strong and sturdy, which helps winter dormancy.

4. Light

Hydrangea prefers shade. After being moved outdoors in spring, it should first be placed in a semi-shaded environment for care; in midsummer, move it to a well-ventilated, cool place to prevent sunscald on the leaves. After September, as light intensity gradually weakens, move the pot to a brighter spot to promote flower bud differentiation.

5. Temperature

The suitable growing temperature for hydrangea is 18 to 28°C, and the winter temperature should not fall below 5°C. Flower bud differentiation requires 6 to 8 weeks at 5 to 7°C; a temperature of 20°C can promote flowering, and maintaining 16°C after the flowers appear can extend the viewing period. However, high temperatures make the flowers fade quickly.

6. Pinching

When new branches grow to about 10 to 15 cm, they can be pinched to encourage branching; when the branches reach 8 to 10 cm, pinch a second time to help the plant form a neat, well-balanced shape. Flower bud differentiation occurs after September; after the flowers fade, shorten the branches promptly to encourage new growth, and when the new branches reach 8 to 10 cm, pinch again to make the new buds plump, which benefits flowering the following year. Thereafter, every year in early spring in March, cut away diseased, dead and weak branches from the base, keep 3 to 5 vigorous main branches and shorten them, leaving 2 to 3 buds per branch to encourage new shoots and abundant flowering. Through pruning and shaping, the plant can be made compact, full, symmetrical, with many large, brightly colored flowers. Without pruning, the base of branches more than 3 years old has already become woody and does not readily sprout new growth, easily leaving the lower part of the plant bare and reducing its ornamental value.

Precautions for Growing Hydrangea

1. Hydrangea prefers acidic soil and does not tolerate poor, saline-alkaline soil. It grows poorly in alkaline soil, with yellowing branches and leaves, and does best in loose, fertile, humus-rich acidic soil. Its flower color is affected by pH and can change from white to red, and from red to blue.

2. Move it indoors in early to mid-October, control watering, and keep the room temperature at around 5°C to encourage dormancy. Before bringing it indoors, remove the leaves to prevent them from rotting. Starting in mid-December, move it to a sunny spot and keep the temperature at 15 to 20°C to promote the growth of branches and leaves, then move it outdoors in late April the following year.

3. During a year's growing period, the plant can generally be topped twice to encourage branching. After flowering, shorten the old branches to 1 to 2 nodes to control plant height and encourage new growth. After autumn, cut off the tips of new shoots to stop branch growth, which helps overwintering.

4. Cuttings taken in March can be moved into 10 cm pots after rooting, then planted in 16 cm pots in mid-June. Pinch for the first time in June. If pinched in early June, flower buds can form by mid-August. Cuttings taken in May to June can be planted in 16 cm pots in July to August; to encourage flower bud formation that same year, the final pinching must be done before September, otherwise no flower buds will form that year.

Main Value of Hydrangea

1. Hydrangea has full, large and beautiful flower heads, and its flowers can be red or blue, making it pleasing to the eye and refreshing to the spirit; it is a common potted ornamental flowering plant.

2. Cutting off the entire flower head and placing it in a vase indoors also makes an elegant decoration. Hanging the flower head inside a bed canopy feels even more refined and charming.

Note: Once hydrangea is eaten, abdominal pain appears within a few hours; other typical poisoning symptoms include skin pain, vomiting, weakness and sweating, and there are reports that patients may even experience coma, convulsions and collapse of blood circulation in the body.