A Detailed Guide to the Cultivation Techniques and Management Methods of Oleander

Oleander (Neriummdcum), also known as willow-leaf peach and half-year red. Apocynaceae, genus Nerium. It gets its name because its flowers resemble peach blossoms and its leaves resemble bamboo. The flower colors are gorgeous, either pink, like peach blossoms, plump and vivid; or pure white, bright and clean as snow, crystal clear and dazzling, appreciated by people since ancient times. It is cultivated everywhere, and is an excellent flowering shrub that blooms in summer and autumn and can resist pollution.

(1) Morphological characteristics and varieties

Evergreen large shrub, plant height can reach 4 m to 5 m, crown spreading, branches upright and smooth, clumping, young branches angular, strong branching ability, mostly growing in a three-forked pattern. Leaves lanceolate, usually 3 to 4 leaves whorled, middle and lower parts of branches mostly opposite, thick leathery, midrib obvious, entire margin, with short petiole, a small amount of milky sap in branches and leaves. Cymes terminal, corolla funnel-shaped, 5-lobed, petals wrinkled, lobes twisted to the right, pink to deep red, most are double and semi-double. Flowering period long, from June to October, with flowers appearing successively. Fruit oblong, horticultural varieties very many, common ones include white-flowered oleander, red-flowered oleander, etc.

(2) Ecological habits

Oleander is native to India, Iran, and Afghanistan. It prefers a warm and humid climate and is not very cold-hardy. It can be planted in the open ground in areas south of the Yangtze River Basin in China, but in Nanjing the branches and leaves are sometimes frozen and withered, and young seedlings may even freeze to death. In the north it can only be grown in pots for ornamental purposes, overwintering indoors. The white-flowered variety is slightly more cold-hardy than the red-flowered variety. Oleander is not tolerant of waterlogging, and planting sites should be chosen that are high and dry with good drainage. It likes light and fertilizer, and can also adapt to a relatively shady environment, but when planted in shade, the flowers are fewer and the color is pale. Its ability to resist air pollution is relatively strong, and its resistance to toxic gases such as sulfur dioxide, chlorine gas, and smoke dust is very strong, and its absorption capacity is also relatively strong, so it is an excellent tree species for greening and decoration in industrial and mining areas and railway platforms. It has strong sprouting ability, and the tree body recovers easily after damage.

(3) Propagation methods

Cuttage propagation is the main method, and division and layering can also be used. Cuttage can be carried out in both spring and summer. Soak the base of the cuttings in clean water for about 10 days, keep the soaking water fresh, and after planting they will root earlier and the survival rate will also be high. The specific method is: in spring, cut 1- to 2-year-old branches into stem segments 15 cm to 20 cm long, tie about 20 of them into a bundle, soak them in clean water with the submerged depth being 1/3 of the stem segment, change the water at the same temperature once every 1 to 2 days, keep the temperature at 20C to 25C, and when adventitious roots are found on the soaked part, they can be cut. When cutting, make holes in the cutting medium with bamboo chopsticks to avoid damaging the adventitious roots. Because the sprouting ability at the base of old oleander stems is very strong, a large number of young shoots are often produced, and these branches can be fully used for summer softwood cuttage. Select semi-lignified cuttings, keep the top 3 small leaves, insert them into the substrate, and pay attention to timely shading and water management; the survival rate is also very high. When propagating by layering, first scarify or girdle the part to be buried, bury it in soil, and after about 2 months it can be cut from the parent plant and transplanted with soil the following year.

(4) Cultivation techniques

Oleander has strong adaptability, and cultivation and management are relatively easy, whether planted in the ground or in pots, and both are relatively extensive. In places where it is planted in the ground, transplanting should be done in spring, and heavy pruning should be carried out when transplanting. Pay attention to protection in winter. Branches and leaves are easily damaged by scale insects, so attention should be paid to prevention and control.

For potted oleander, in addition to requiring good drainage, sufficient fertility is also needed. In spring, shaping and pruning are needed when it sprouts. For leggy branches and weak slender branches in the plant, they can be cut off from the base, and for overly dense inner branches, part of them should also be thinned so that the branches are evenly distributed and the tree shape remains full. After 1 to 2 years, repot once, and repotting should be done after pruning. Summer is the period of vigorous growth and flowering for oleander, and the water requirement is large. In addition to watering once each morning and evening every day, if the potting soil is seen to be too dry, an additional spraying should be added to prevent young branches from wilting and to avoid affecting the lifespan of the flowers. After September, water should be withheld to inhibit continued growth of the plant, make the branch tissues mature, increase nutrient accumulation, and help it overwinter safely. The overwintering temperature needs to be maintained at 8C to 10C; below 0C, it will shed leaves.

Oleander is a fertilizer-loving plant. For potted plants, in addition to applying sufficient base fertilizer, a topdressing of fertilizer should be applied once a month during the growing period.

(5) Ornamental value and applications

In the season when few flowers bloom in summer, oleander blooms for nearly 4 months, making it a rare summer flowering tree species. It can be planted on both sides of buildings, in parks, green spaces, roadsides, poolside, and other sections, and is even more suitable for planting in industrial and mining areas and along railway lines for pollution resistance.

The stems and leaves are toxic, so attention should be paid during pruning and cuttage.