How to Grow and Care for White Orchid Tree (Michelia alba) in the North? Detailed Methods and Techniques
Michelia alba, also known as huanggelan, belongs to the Magnoliaceae family as an evergreen broadleaf tree, generally grown in subtropical regions; in northern areas it can only be cultivated as a potted plant. But quite a few northern gardening enthusiasts say Michelia alba is hard to care for and may even die entirely if not handled properly. Here is how to grow and care for Michelia alba in the North.
I. Choice of Potting Soil
When choosing potting soil for Michelia alba, two points should be noted: first, Michelia alba has fleshy roots and prefers soil with good permeability; second, Michelia alba is a southern flower and prefers acidic soil. In view of these two points, the author once used two groups of soil for a cultivation comparison. The first group used the plain sandy soil commonly used in northern areas, and the second group used a cultivation soil made by mixing coarse river sand, sandy loam and leaf mold in a 1:1:1 ratio. Observation showed that, under the same conditions of plant status, water, fertilizer, light and temperature, the second group grew better. It should be noted that northern soil is relatively alkaline, so when mixing the cultivation soil, an appropriate amount of ferrous sulfate or sulfur powder should be added to increase the acidity of the soil.
II. Water and Fertilizer Management
When cultivating Michelia alba in northern areas, watering is crucial. That Michelia alba likes a humid environment essentially means the air humidity is high but the soil water content must not be too high. According to the author's experience, when watering Michelia alba, in spring it can be given a thorough watering once a week, in summer a thorough watering once each morning and evening, in autumn a thorough watering once every 4 to 5 days, and in winter indoors a thorough watering about once every 10 days; on cloudy or rainy days in summer, water less or not at all. It must never be exposed to rain; if it does get rained on, the accumulated water in the pot should be poured out promptly, and the plant placed in a shaded, ventilated spot; after the potting soil is slightly dry, the soil should also be loosened to help water evaporate. In daily care, note also that no matter the season, as long as the surrounding temperature is above 10°C, the leaves should be misted with water, as follows: once every 2 to 3 days in winter, once every 1 to 2 days in spring and autumn, and once each morning and afternoon every day in summer. Northern water is relatively alkaline, and long-term use easily makes the soil alkaline, so use rainwater, snow water or ferrous sulfate water. But rainwater and snow water are not easy to store; if tap water is normally used, watering with ferrous sulfate water at regular intervals (about every 10 days) will also prevent the plant from getting chlorosis.
When fertilizing Michelia alba, two principles must be grasped: first, balanced nutrition; second, frequent application of thin fertilizer. Balanced nutrition means applying different fertilizers according to the plant's different needs at different stages; if this point is not grasped well, it is not conducive to plant growth and flowering. For example, some gardening enthusiasts apply nitrogen fertilizer during the summer flowering period, causing excessive growth of branches and leaves and a lack of phosphorus, making it difficult to form flower buds. When fertilizing Michelia alba, in early spring nitrogen fertilizer should be dominant, and in summer and autumn phosphorus and potassium fertilizers should be dominant. In addition, when fertilizing, organic and inorganic fertilizers should be used alternately, and they can also be mixed. Long-term application of inorganic fertilizer easily makes the potting soil compact and affects root respiration. For organic fertilizer, sesame paste residue, chicken manure, pigeon manure, and the commonly used base fertilizer horseshoe slices can be chosen. Frequent application of thin fertilizer means the amount applied at one time should not be too large; apply less but often. According to the author's experience, for inorganic fertilizers such as urea, the amount at one time is 5 grams to 10 grams; sesame paste residue, chicken manure and pigeon manure can be applied at 50 grams at one time; alum fertilizer water and horseshoe water should be diluted with clear water at a 1:1 ratio of stock solution to water. It should be mentioned that organic fertilizer must be fully decomposed and fermented before use; raw fertilizer very easily burns the plant's roots. As for the frequency of fertilization, generally speaking, once every 15 days in spring and autumn, once every 10 days in summer (flowering period), and generally no fertilization in late autumn and winter.
III. Light and Temperature Control
Michelia alba is not strict about light, but overly strong or insufficient light is unfavorable to plant growth. Too strong light easily scorches the leaves, while insufficient light makes it difficult to form flower buds, and even if there are flowers, they are not fragrant. In spring, after the Mid-Autumn Festival and in winter, it should be placed in a sunny spot to receive light. In summer and early autumn, it should be placed in a semi-shaded spot, with 50% of the light blocked, so that it receives sunlight before 9 a.m. and after 6 p.m., avoiding direct exposure to the strong midday sun.
Michelia alba likes a warm environment. When cultivated in the North, it should be moved out of the shed in spring after the temperature stabilizes around Grain Rain. In summer, as long as there is no strong light exposure and water can keep up, Michelia alba is not afraid of high temperatures. After mid-October it should be moved into the shed promptly, because Michelia alba cannot tolerate low temperatures below 5°C. In winter the indoor temperature should be kept between 5°C and 15°C. If the temperature is too low, damage easily occurs; if the temperature is too high, it is not only unfavorable for the plant's dormancy, but also affects flowering the next year and easily exposes the plant to pests and diseases. Some gardening enthusiasts, too eager to love their flowers, fear the flowers will freeze to death and place them near a heat source, only to get the opposite result: the newly sprouted tender leaves easily fall off due to insufficient light, water and fertilizer, which both consumes nutrients and prevents normal growth. If the indoor temperature cannot meet the overwintering requirements, the method of covering the flowerpot with agricultural film can be used to solve the problem and help the plant overwinter.
IV. Repotting and Pruning
Michelia alba is generally repotted once every 2 years, and each repotting should use a pot one size larger; repotting can be done in spring after the plant is moved out of the shed. New pots should be subjected to a de-firing treatment, and the bottom of the pot should be given a drainage layer of broken tiles; on the drainage layer spread about 3 cm of cultivation soil, then place 3 to 4 horseshoe slices as base fertilizer, then spread another layer of cultivation soil; knock the plant out of the original pot, cut off dead roots and rotten roots, place it in the new pot, fill in soil layer by layer and press firmly, then immediately water thoroughly once.
Michelia alba has poor sprouting ability, so vegetative branches are generally not pruned, but it is necessary to cut off dead branches and diseased or pest-infested branches. Properly removing some leaves during the bud stage helps flower bud formation, can make the flower buds larger, and can prolong the flowering period.
V. Pest and Disease Control
Common diseases of Michelia alba include anthracnose, leaf spot and chlorosis, and the main pests include red spider mites, scale insects and aphids. In daily care, besides strengthening water and fertilizer management to improve the plant's disease resistance, attention should also be paid to ventilation. If pests occur, when the number is small they can be removed by hand; when the number is large, 40% dicofol 1000-fold solution can be sprayed to kill red spider mites, and 40% omethoate emulsifiable concentrate 1000-fold solution can be sprayed to kill scale insects and aphids. For anthracnose and leaf spot, broad-spectrum agents such as chlorothalonil and carbendazim can be used for control. For chlorosis, foliar spraying with 1/800 ferrous sulfate water can be used for control.