How to Revive a Magnolia That Has Grown Poorly for Years

Growing Techniques Jan 1, 1970 0 views

Magnolia flowers

Magnolia is an important early-spring flowering tree species. Its flowers are pure white and elegantly understated, fragrant, and large, deeply loved by people, and widely used in landscaping. Recently, a special correspondent of China Landscape Web saw a weak-growing magnolia in a residential community, with pale yellow leaves and leaf spot disease, and thin, short, and sparse branches. It is understood that this magnolia had been planted for 12 years. Although its growth was not vigorous, it had survived tenaciously and bloomed every year, but the flowers were few and small, and the flowering period was relatively short. According to the greening worker responsible for maintenance, when this magnolia was first planted, its diameter at breast height was 6 cm. After many years of planting, it had not thickened, and its current diameter at breast height showed no obvious change from when it was planted, making it a veritable "small old tree."

What caused the magnolia to become a "small old tree"? A special correspondent of China Landscape Web, together with local technicians and maintenance workers, investigated the causes. According to the observations of the special correspondent of China Landscape Web, the magnolia was planted in front of a five-story building, in a typical sheltered, sunny location. Around it was cool-season turfgrass, in front of the magnolia was a big-leaf boxwood pattern planting, and beside the magnolia were planted elm-leaved spirea and yellow rose. Apart from the magnolia, all the other plants grew vigorously.

According to the greening maintenance staff, because the trees had been planted for many years, this green space was rarely fertilized, including the magnolia. Every year the trees were given thawing water and freezing water, and at other times the magnolia was watered only incidentally while the lawn was being irrigated; the magnolia was never watered separately. Considering that the magnolia's leaves were small and yellowing, we first started from the perspective of analyzing the soil. Through observation, the soil at the planting site was black soil, somewhat clayey, and rather compacted. Laboratory testing of the soil's salinity and pH value showed a salinity of 0.2% and a pH value of 8.8, belonging to mildly saline-alkaline soil. The special correspondent of China Landscape Web dug deeply into the soil and found no bricks, tiles, or other debris. According to the greening construction supervisor at the time, the base layer of the green space was very clean, and the original soil had already been reached. Based on this, we can judge that soil structure was not the cause of the magnolia becoming a "small old tree"; the soil being somewhat clayey, compacted, and having excessive salinity and pH value were the main reasons leading to the magnolia becoming a "small old tree."

Why is this said? First, magnolia prefers sandy loam with good permeability, and it also has requirements for soil fertility; it does not like poor, thin land. In addition, magnolia prefers acidic soil and can grow normally in neutral to acidic soil, but this plot of land belongs to mildly saline-alkaline soil, which therefore affected the magnolia's growth. Its yellowing leaves and relatively small leaves were both caused by the saline-alkaline soil.

Having found the reasons why the magnolia became a "small old tree," we formulated rescue measures. Everyone agreed that the magnolia had missed the best time for growth and that the tree would thicken very slowly, but through a series of measures the magnolia's growth could be restored, its crown made full and lush, and its flowering increased. First, soil management should be strengthened, with frequent loosening of the planting soil; when necessary, the surface soil could be replaced to a depth of up to 30 cm, and the replacement soil should be somewhat sandy. Second, freezing water and thawing water should be applied well each year; ordinarily the magnolia should be watered separately. During drought, it can be given one thorough watering every half month, and at other times one thorough watering per month. Third, fertilizer management should be strengthened: after flowering in spring, apply nitrogen fertilizer to the plant to promote branch and leaf growth; in autumn, apply phosphorus and potassium fertilizer; in late autumn, in conjunction with watering freezing water, use cow or horse manure or dried chicken powder, and also apply some leaf mold fertilizer. Fourth, irrigate the magnolia with alum fertilizer water once every two months.

How to Restore the Growth of a Magnolia Planted for Many Years

Magnolia flowers

China Landscape Web, August 29 news: Magnolia is an important early-spring flowering tree species. Its flowers are pure white and elegantly understated, fragrant, and large, deeply loved by people, and widely used in landscaping. Recently, a special correspondent of China Landscape Web saw a weak-growing magnolia in a residential community, with pale yellow leaves and leaf spot disease, and thin, short, and sparse branches. It is understood that this magnolia had been planted for 12 years. Although its growth was not vigorous, it had survived tenaciously and bloomed every year, but the flowers were few and small, and the flowering period was relatively short. According to the greening worker responsible for maintenance, when this magnolia was first planted, its diameter at breast height was 6 cm. After many years of planting, it had not thickened, and its current diameter at breast height showed no obvious change from when it was planted, making it a veritable "small old tree."

Magnolia Tree Planting Techniques

Magnolia, also known as white magnolia, Yutangchun, and wood flower tree, is a deciduous tree of the genus Magnolia in the family Magnoliaceae. It is native to Anhui, Zhejiang, Hunan, Hubei, Guizhou, Guangdong, Shanxi, and other regions, and is also widely cultivated in Beijing and areas to the south. Magnolia flowers are pure white, large, and fragrant, and it is an important early-spring flowering tree species in gardens, deeply loved by people. Planted together with crabapple, winter jasmine, tree peony, and osmanthus, it carries the meaning of good fortune and prosperity, and has the laudatory name of “Yutang spring wealth and honor.” The cultivation and management techniques for magnolia are introduced below for reference only.

Common ornamental species in the same genus

The genus Magnolia in the family Magnoliaceae has about 90 species, and China has about 30 species. Common species and cultivars in gardens include: yellow magnolia, purple magnolia, Yulan magnolia, soulangeana magnolia, purple-flowered magnolia, and so on.

Selection of planting environment

Magnolia prefers light; young trees are relatively shade-tolerant and not tolerant of strong light or west-facing sun. Too much light or west-facing sun can easily cause sunscald to the tree. Magnolia can be planted in an environment with lateral shading; planting it under large trees or in a shaded spot leads to poor growth, a thin and small tree form, sparse branches, small and yellowing leaves, and no flowers or small flowers. Magnolia is relatively cold-tolerant and can withstand a brief low temperature of -20°C, but it should not be planted in a wind gap, otherwise shoot dieback is likely to occur. In the Beijing area, in a sheltered, sunny spot, it can overwinter safely in the open ground without measures such as wrapping the trunk. Magnolia prefers fertile, moist, well-drained slightly acidic soil, but it can also grow normally in mildly saline-alkaline soil (pH value 8.2, salinity 0.2%). Magnolia has fleshy roots and fears waterlogging, so the planting site should be high; planting in low-lying areas can easily cause root rot and death. The soil permeability at the magnolia planting site should also be good; planting in clay soil leads to poor growth, while it grows best in sandy loam and yellow sandy soil.

Digging and planting of nursery stock

Magnolia is not tolerant of transplanting. Generally, transplanting 10 to 15 days before bud break or when the flowers have just faded but leaves have not yet unfurled is ideal. Four to five days before digging the seedlings, give them one thorough watering. This not only allows the plants to absorb sufficient water, which helps survival after planting, but also helps the soil form a ball when digging the seedlings. When digging, damage the root system as little as possible, and the wounds on broken roots must be smooth to facilitate wound healing. In addition, note that no matter what size the nursery stock is, it should be dug with a soil ball, and the diameter of the soil ball should be 8 to 10 times the ground diameter of the nursery stock. It must not be too small, or it will not protect the root system. After the soil ball is dug, it should be tied well with straw rope to prevent it from breaking apart during transport.

Before planting, dig the tree hole well. The tree hole should be large rather than small; if the tree hole is too small, it is not only troublesome to plant but also unfavorable for root growth. The bottom soil of the tree hole is best if it is matured soil. If the soil is too clayey or the pH value or salinity exceeds the standard, foreign soil should be brought in or the soil should be improved. The cultivation soil must have good permeability, and the soil fertility must be sufficient to supply the plant with adequate nutrients. There must also be no bricks, tiles, lime, or other debris in the soil. The planting depth should be appropriate. Generally, the planting depth can be slightly 2 to 3 cm above the original soil ball. Too deep and bud smothering is likely to occur; too shallow and the roots will be exposed and the tree can easily be blown over. Large-size nursery stock should be supported with stakes in time; a triangular support can be used to prevent it from being blown askew. After planting is completed, water immediately; after 3 days water a second time, and after 5 days water a third time. After the third watering, normal management can begin. If the planted nursery stock carries flower buds, the flower buds should be pruned off to prevent flowering and fruiting from consuming a large amount of nutrients and affecting the survival rate.

Water and fertilizer management

Magnolia is neither tolerant of waterlogging nor drought. In cultivation and maintenance, the principle that it “likes moisture and fears waterlogging” should be strictly followed. In the process of cultivation and maintenance, many people think that because magnolia fears waterlogging, it should be watered as little as possible. This understanding and practice are completely wrong, because magnolia fearing waterlogging does not mean it likes drought. It itself likes a moist environment, and in water management one must grasp the degree of keeping the soil neither too dry nor too wet. Through many years of cultivation practice, the author believes that during cultivation the soil should be kept moist without standing water. During maintenance, newly planted magnolia should keep the soil moist, which is also an important measure to ensure its survival rate. For magnolia that has entered normal management, the green-up water in early spring and the antifreeze water in early winter are indispensable, and they should be watered sufficiently and thoroughly. During the growing season, water once a month; watering should stop during the rainy season, and drainage should be carried out promptly after rain to prevent root rot caused by standing water. In addition, loosen the soil in time to preserve moisture. It should be noted that irrigation should also be carried out promptly during dry periods in the rainy season. Lack of water not only affects the plant's vegetative growth but can also cause flower buds to fall or shrink, affecting the next year's flowering.

In addition, for 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 at the same time as root watering. Attention should be paid to the degree of atomization in spraying; the higher the degree of atomization, the better the effect. The best spraying times are before 8:00 a.m. and after 6:00 p.m.; spraying cannot be done at noon when light is strong. For magnolia that has suffered waterlogging damage, it should be rescued immediately. First, the standing water should be drained promptly. Second, the tree should be shaded, especially to prevent west-facing sun. Third, some leaves and flower buds should be pruned off.

Magnolia likes fertilizer. In addition to applying base fertilizer at planting, it should be fertilized every year thereafter. Sufficient fertilizer can make the plant grow vigorously, with lush, thick green leaves, not only producing many flower buds but also large flowers, a long flowering period, and rich fragrance. Fertilize magnolia 4 times each year: apply a nitrogen, phosphorus, and potassium compound fertilizer once before flowering; this fertilization can not only improve flowering quality but also benefit spring growth. Apply a nitrogen fertilizer once after flowering; this fertilization can increase the plant's growth and expand its nutritional area. Apply a phosphorus and potassium compound fertilizer once in July and August; this fertilization can promote flower bud differentiation and increase the degree of lignification of new branches. Before winter, in conjunction with watering winter water, apply a fully decomposed and fermented barnyard manure once; this fertilization can not only improve soil activity but also effectively raise soil temperature, and the amount applied should be large rather than small. In addition, for 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 strengthen the tree's vigor.