How to Grow Hydrangea? Master These Key Cultivation Techniques

Hydrangea, also known as bigleaf hydrangea, is a deciduous small shrub in the Hydrangea genus of the Saxifragaceae family, with emerald green leaves, bright flower colors, and a long ornamental period, and is deeply loved by people.

Plant Characteristics Hydrangea is native to China's Yangtze River basin and the provinces to its south, with a natural plant height of 1 to 2 m, and the potted height is mostly controlled at 30 to 50 cm. The leaves are opposite, obovate or elliptical, with serrated margins. The corymb is terminal, 20 cm in diameter, nearly spherical, with few and small fertile flowers and numerous and large sterile flowers. The flower color is variable, initially white, gradually turning blue or pink, with a natural flowering period from May to July.

Ecological Habits Hydrangea prefers a warm and humid environment, with an optimum growth temperature of 18°C to 28°C, and no lower than 5°C in winter. Light should be semi-shaded; too strong light will scorch the leaves and cause curling at the edges. It prefers loose and fertile soil, has a high water requirement, but dislikes waterlogging, and has strong resistance to harmful gases such as sulfur dioxide.

Common Cultivated Varieties Hydrangea macrophylla (V. hortensica): all flowers are sterile, with ovate sepals. Blue-edged hydrangea (V. coerulea Wils): flowers are bisexual, deep blue, with marginal flowers blue or white. Ziyang flower (V. otaksa Bailey): flowers are sterile, the inflorescence is large, up to 20 cm in diameter, the leaves are thick, the inflorescence is spherical, blue or light red, and it is mostly used in gardens. Silver hydrangea (V. maculata Wils): divided into fertile and sterile types, with relatively narrow and small leaves and white margins, used for foliage viewing.

Propagation Methods Hydrangea can be propagated by division, layering, cuttings, and other methods.

In a greenhouse, cuttings can be taken throughout the year. Generally, in May to June, this is done in combination with early spring pruning and post-flowering shaping. Select semi-lignified branches free of pests and diseases, each 10 to 15 cm long, retain 2 to 3 nodes and 1 to 2 leaves at the top, and insert them into a seedbed with river sand or vermiculite as the substrate, with appropriate shading. Keep the substrate moist and the air humidity above 80%, and rooting begins in about 18 days. After that, gradually reduce the frequency of misting and increase light, and transplanting can be done in about 1 month.

Cultivation Management After the cutting seedlings root, they should be potted in time. Hydrangea prefers loose, fertile, and well-drained soil, usually prepared with leaf mold, garden soil, and organic fertilizer in a 4:4:2 ratio. For large-scale production, it is advisable to use peat, perlite, and organic fertilizer in a 6:2:2 ratio, and disinfect thoroughly before use.

Fertilization Hydrangea prefers fertilizer, generally applying organic fertilizer once every half month. In the early growth stage, more nitrogen fertilizer is needed; during flower bud differentiation and flower bud formation, more phosphorus and potassium fertilizer is needed. You can also spray the leaves 2 to 3 times with 0.1% to 0.2% potassium dihydrogen phosphate, and stop fertilizing after the flower buds color up.

Watering The transpiration rate of hydrangea leaves is very high, so watering must be timely; even short-term water deficiency and wilting can cause dry leaf edges and necrotic flowers. Especially in summer, shading and cooling must be used to reduce transpiration, and air humidity should be kept above 60%. In addition, hydrangea flower color is affected by soil pH, usually appearing blue in an acidic environment and red in an alkaline environment. Therefore, the pH of the water should be determined according to the desired flower color.

Temperature Hydrangea is not tolerant of high temperatures and requires a temperature between 15°C and 25°C. High temperatures will make the plant shorter and the flower color lighter, reducing quality. After the flower buds color up, keep the temperature at 10°C to 12°C to improve flower color and preserve freshness.

Light Hydrangea is shade-tolerant, and direct sunlight can cause sunscald, so shading is needed. Generally, 60% shading is required during the growth period, and appropriate shading is also needed after the inflorescence colors up, so as to avoid the flower color fading and losing its luster.

Pruning Hydrangea has strong sprouting ability, and many vegetative branches will sprout from the base of the plant. To reduce nutrient consumption, they should be removed in time. If old branches need to be replaced, vigorous vegetative branches can be selected as reserve branches. After flowering, cut back promptly, retaining 2 to 3 vigorous buds to promote new branches.

Flowering Regulation To make hydrangea bloom during the Spring Festival, select vigorous 3- to 5-year-old plants, treat them at a low temperature of 2°C to 4°C for 14 days, then move them into a greenhouse for heating, maintain 10°C to 20°C, and they can bloom in 50 to 60 days. Pay attention to frequent ventilation, maintain good light conditions and relatively high air humidity, and apply an organic liquid fertilizer once every half month until flowering.