What are the methods for growing magnolias in pots?
Magnolias are fresh and elegant, and are important plants for beautifying courtyards. In magnolia cultivation, note the following: Magnolia is a spring-flowering tree valued for both color and fragrance. When planting, the timing must be well controlled, neither too early nor too late. The most suitable time is 10 days before bud break in early spring, or after the flowers fade but before the leaves unfold. When transplanting, regardless of the size of the seedling, the roots must be kept with a ball of soil, and care should be taken not to damage the root system as much as possible, to ensure survival. Before planting, apply plenty of fully decomposed organic fertilizer in the hole as a base fertilizer. After planting, firm the soil and water thoroughly in good time.
Magnolias prefer fertilizer, but dislike heavy fertilization; during the growing season, applying fertilizer twice is generally enough to favor flower bud differentiation and promote growth. One application is in early spring, and the other in May-June. The fertilizer is mostly fully decomposed organic fertilizer. Newly planted saplings need not be fertilized; wait until after leaf drop or the following spring to fertilize. The magnolia root system consists of fleshy roots and does not tolerate waterlogging. During flowering and growth, the soil should be kept slightly moist. After autumn begins, watering should be reduced to delay root growth, promote the ripening of the branches, and help the plant overwinter. In winter, generally do not water, and water only once if the soil becomes too dry. Magnolia branches and trunks have poor wound-healing ability, so pruning is generally not carried out. However, for a reasonable tree shape, water sprouts, dead branches, diseased and pest-infested branches, and branches that spoil the tree's appearance should still be cut off in the early leaf-unfolding stage. In addition, after the flowers fade, if seed is not wanted, the spent flowers and follicle clusters should also be cut off to avoid consuming nutrients and affecting the next year's flowering.
Magnolias are mostly grown in the ground; when potted, they are best trained as bonsai-style specimens.
Magnolias can be propagated by grafting, layering, cuttings, sowing and other methods, but the two most commonly used are grafting and layering.
The white magnolia (Magnolia denudata) likes a sunny and humid environment and is not suitable for long-term growth in alkaline soil. For planting, choose a spot sheltered from wind, facing the sun, with good drainage and fertile soil. Before flowering, there should be sufficient water and fertilizer to promote large, fragrant flowers. Magnolia branches are not numerous; apart from dead branches, diseased and pest-infested branches, and branches that spoil the tree shape, pruning is generally unnecessary. After the flowers fade, if seed is not wanted, the fruit should be cut off to avoid consuming nutrients. The white magnolia is fairly cold-hardy and can overwinter outdoors in North China and the southern part of Northeast China.
For potted magnolias, wiring and bending can be done: that is, after sprouting in April, as the new shoots grow, wire and bend them at any time into curved shapes to limit the trunk from growing tall. Also, because magnolia has a deep root system and tends to weaken after long periods in a pot, after the flowers fade the main roots should be trimmed and the plant grown in the ground, then repotted before flowering; only in this way will the flowers be abundant and vivid.
If propagated by seed, the maturity period of the seeds must be well judged: collect them when the follicles turn red and split open. Collecting too early means they will not germinate; collecting too late means they easily fall off. After collecting the follicles, spread them out thinly, soak the fruits with the red outer seed coat in cold water and rub and wash them, remove the outer seed coat completely, take out the seeds, dry them in the shade, stratify them in sand storage, and sow in February-March the following year. One-year-old seedlings can reach about 30 cm in height. Those growing larger seedlings should transplant them the next spring, appropriately cut the main root, apply heavy base fertilizer, and control density; in 3-5 years, qualified seedlings with a complete crown, occasional flower buds, and a plant height of more than 3 m can be produced. Two to three years after planting out, they enter full bloom. Such seedlings grow vigorously and have strong adaptability, and their results are no inferior to grafted seedlings.
Cuttings are the main propagation method for the purple magnolia (Magnolia liliiflora). The cutting time has a great influence on the survival rate; it is generally done in May-June, and current-year shoots from young trees give the highest survival rate as cuttings. Soaking the base in 50 ppm naphthaleneacetic acid for 6 hours can increase the rooting rate.
Layering is a traditional propagation method, suitable for preserving and developing famous and superior cultivars. The purple magnolia is best propagated this way. Select a well-growing plant, take 1-2 year old branches 0.5 cm to 1 cm thick as layers; if there are side branches, they can be layered on the branches. The layering time is February-March. Roots form the same year after layering, and the longer the layer remains connected to the mother plant, the more developed the root system and the higher the survival rate. Two to three years after planting out, it can bloom.
In recent years, tissue culture has been used, with buds of the Yulan magnolia (Magnolia x soulangeana) as explants, and successfully cultured in test tubes. This method is of special significance for preserving and developing new types bred through bud sports and hybridization.