What are the management key points for unrooted hydrangea seedlings?

Hydrangea (scientific name: Hydrangea macrophylla), also known as hydrangea or ajisai, is a plant of the genus Hydrangea in the family Saxifragaceae. The flowers of hydrangea are pure white and full, large and beautiful, and their color can be red or blue, making them pleasing to the eye and refreshing to the mind. It is a common potted ornamental flowering shrub. China cultivated hydrangea relatively early, and hydrangea was planted in the Jiangnan gardens built during the Ming and Qing dynasties. The parks built in the early 20th century also could not do without the arrangement of hydrangea. Modern parks and scenic areas all plant them in masses to form landscapes.

1. Preparation before arrival

1. Greenhouse conditions

A solar greenhouse or modern glass greenhouse is acceptable, but there must be heating and cooling facilities such as fans, water curtains, and heating.

2. Plug trays

Use 50-cell or 35-cell plug trays.

3. Substrate

Generally, the growing medium is required to have good aeration, water-holding capacity, and buffering performance, and to be relatively stable. Substrate mixtures that do not contain peat and clay can all be used for production. The seedlings treated with a perlite and humus soil mixing ratio of 1 to 2 are the most robust. Red and pink varieties require a substrate pH of 5.5 to 6.0. Blue and white varieties are suitable for a pH of 3.5 to 4.0.

4. Water

Rainwater (or a mixture of tap water and rainwater) is the ideal irrigation water (pH around 7).

2. Cuttage

Hydrangea takes about 35 weeks from unrooted seedling to market, and finished products for New Year's Day market need to be cut in late March or early April of the previous year. It is ideal for cuttings to root in seedling trays or single seedling bags. But the key to success lies in the selection of the substrate, and it must be ensured that the selected substrate is not too hard, so as to facilitate the rooting of the cuttings. Hydrangea is very sensitive during the rooting stage.

3. Rooting conditions

1. Temperature

During rooting, keeping the temperature at 18°C to 20°C and a high-humidity environment is relatively ideal, especially after cuttage. Because if the substrate temperature is too high, the root growth rate will slow down or even stop; while if the air temperature is too high, it will cause the plant stems to become slender and weak, and the root system may also stop growing accordingly.

2. Light and humidity

After cuttage, proper shading should be provided and management strengthened. Generally, the relative air humidity is 80% to 90%. When the seedlings have grown for 20 days to 25 days and the root system has filled the nutrition pot or plug tray, they can be potted.