Cultivation and Management Techniques for Yulan Magnolia in North China
Yulan magnolia (Magnolia denudata) is a deciduous tree of the genus Magnolia in the family Magnoliaceae, native to Jiangxi, Zhejiang, Hunan and other places, and is also widely cultivated in areas south of Beijing. Its flowers are pure white, large and fragrant, making it an important early-spring flowering tree species in gardens. Its cultivation and management techniques in North China are described below.
Growth habits of Yulan magnolia
Yulan magnolia likes light and is slightly shade-tolerant, and can be planted under conditions of lateral shading, but should not be planted under large trees or in shady spots; Yulan magnolia is relatively cold-hardy, and in sheltered, sunny spots in the Beijing area it can overwinter safely in the open ground without measures such as wrapping the trunk; it likes fertile, moist, slightly acidic soil, but can also grow normally in mildly saline-alkaline soil (pH 7 to 8.2, salt content below 0.2%); Yulan magnolia has fleshy roots and fears waterlogging, so the soil at the planting site should have good permeability, with sandy loam being preferable.
Selection and planting of seedlings
The selection of seedlings is directly related to the survival rate of planting and the future ornamental effect, so the selection of seedlings must be strictly controlled. In addition to determining the specifications of the seedlings according to greening needs, the following points should also be grasped when selecting seedlings: First, the seedlings must not have pests or diseases; when selecting seedlings, carefully inspect the tree body to see whether there are mycelia, disease spots or decay, and carefully check whether there are insect holes, live insects, eggs or cocoons; if so, try not to select them. Second, choose seedlings with a good tree shape; the main trunk of the seedling should be straight, the main branches and lateral branches should be evenly distributed, there should be no uneven crown, and the top shoot should remain intact. Third, pay attention to checking whether the tree body has bark injuries; if there are bark injuries or splits, they will affect the transport of nutrients and water, which is not conducive to the survival of the seedling. Fourth, after selecting the seedlings, when lifting them the plant must have a soil ball, and the diameter of the soil ball should be 8 to 10 times the diameter at breast height; after the soil ball is dug, it should be tied well with straw rope to prevent it from breaking apart during transport.
In order to ensure the survival rate of the seedlings, the following aspects should also be given more attention during planting. First, the best planting time is before flowering in early spring. Second, the tree pit should be large rather than small; if the tree pit is too small, it is not only troublesome to plant, but also unfavorable to root growth. Third, if the soil is too clayey or the pH value is too high, the soil should be replaced with imported soil. Fourth, the subsoil is best if it is matured soil and should be mixed evenly with base fertilizer. Fifth, the planting depth should be appropriate; generally speaking, the planting depth of the seedling can be slightly 2 to 3 cm above the original soil ball; too deep and it is prone to bud suffocation, too shallow and the roots will be exposed. Sixth, large seedlings should be promptly supported to prevent them from being blown askew by the wind. Seventh, after planting is completed, the first watering should be done immediately, the second watering three days later, and the third watering five days later. Eighth, if the planted seedling has flower buds, the flower buds should be cut off to prevent the plant from consuming a large amount of nutrients through flowering and fruiting, which would affect the survival rate.
Water and fertilizer management
Yulan magnolia likes moisture and fears waterlogging, and this principle should be strictly grasped in cultivation and maintenance. However, in practice many people think that because Yulan magnolia fears waterlogging, it should be watered as little as possible. They do not realize that fearing waterlogging does not mean liking drought; Yulan magnolia itself likes a moist environment, so how should this degree be controlled? The author believes that during cultivation, the soil should be kept moist but not waterlogged. During maintenance, the surface soil of newly planted Yulan magnolia must remain moist, which is also an important measure to ensure its survival rate. After entering normal management procedures, the green-up water in early spring and the antifreeze water in early winter are indispensable. In other seasons, whether to water can be determined according to soil moisture and rainfall conditions, and in the rainy season the soil should also be loosened in time to preserve moisture. During dry periods in the rainy season, irrigation should also be carried out in time; lack of water will not only affect vegetative growth, but can also cause flower buds to drop or shrink. It should be mentioned that for Yulan magnolia planted in poor site conditions, especially in environments with a large hardened area and a small green area, under continuous high temperature and drought weather, foliar spraying should be carried out while watering the roots; attention should be paid to the degree of atomization during spraying, and the higher the degree of atomization, the better the effect; the best spraying times are before 8 a.m. and after 6 p.m., and spraying cannot be carried out at noon when light intensity is strong.
Yulan magnolia likes fertilizer. In addition to applying base fertilizer at planting, topdressing should be carried out every year; sufficient fertilizer can make the plant grow vigorously, with more and larger flowers and a longer flowering period. Yulan magnolia can be fertilized 4 times a year, namely: apply a nitrogen, phosphorus and potassium compound fertilizer once before flowering; this fertilization can improve the quality of flowering and benefit spring growth. Apply a nitrogen fertilizer once after flowering, which can increase the plant's growth amount and expand the nutritional area. Apply a phosphorus and potassium compound fertilizer once in July and August; this fertilization can promote flower bud differentiation and improve the degree of lignification of new shoots. Before winter, apply a fully decomposed and fermented barnyard manure once together with winter watering; this fertilization can improve soil activity and can effectively raise ground temperature. In addition, for small seedlings planted in the same year, if their growth is poor, a 0.2% potassium dihydrogen phosphate solution can be used for foliar spraying, which can effectively improve tree vigor.
Overwintering management
Yulan magnolia planted in the same year should have overwintering management strengthened. In addition to timely and thoroughly watering the freezing water, the tree pit should also be treated by covering with grass, covering with film or hilling soil, and the tree body can be treated by whitewashing. For Yulan magnolia that has survived planting for many years, only antifreeze watering and whitewashing are needed.
Pest and disease control and pruning and shaping
Yulan magnolia is a tree species with relatively strong resistance. Its main diseases include black spot, chlorosis and leaf scorch. Black spot is caused by infection by Deuteromycetes; if it occurs, broad-spectrum fungicides such as 70% mancozeb 500 times solution and 75% chlorothalonil 800 times solution can be sprayed on the leaves for control. In daily maintenance, attention should also be paid to ventilation and light transmission, and water and fertilizer management should be strengthened to improve the plant's disease resistance. Chlorosis is a physiological disease, mainly caused by overly alkaline soil; for this disease, ferrous sulfate (0.2% solution) can be applied to adjust the pH, and more farmyard manure should be applied. Leaf scorch has many causes, mainly poor site conditions (such as a large hardened area, small green area, etc.), long periods of high temperature and drought, soil alkalinization or excessive flowering, etc.; comprehensive control measures such as increasing the number of waterings, applying more fertilizer and whitewashing the trunk can be adopted. Yulan magnolia occasionally suffers from pests such as bagworms and Psilogramma menephron in North China; if they occur, 20% diflubenzuron 8000 times solution or 50% zinc phoxim 1000 times solution can be sprayed for killing.
Because the healing ability of Yulan magnolia branches and trunks is relatively poor, pruning is generally not done unless necessary. If the tree shape is unattractive or relatively messy, diseased and pest-damaged branches, dried branches, drooping branches, water sprouts, overly dense branches and useless branches can be removed according to the actual situation, so as to facilitate ventilation and light transmission and produce a beautiful tree shape. The pruning time is before leaf expansion in early spring. Yulan magnolia is generally not headed back, so as to avoid cutting off flower buds.