A Detailed Guide to Oleander Propagation Methods and Key Management Points
Propagation Methods Oleander can be propagated by three methods: cuttings, division, and layering, among which cuttings are the most commonly used propagation method.
Cuttings can be taken in both spring and summer. If, before planting, the base of the cutting is soaked in clear water for 7 to 10 days, keeping the soaking water fresh, roots can form earlier after planting and the survival rate increases. The specific method is: take 1- to 2-year-old branches cut in spring, cut them into stem segments 15 cm to 20 cm long, tie about 20 of them into a bundle, and soak them in clear water with the submerged depth being 1/3 of the stem segment, changing the water at the same temperature once every 1 to 2 days, keeping the temperature at 20°C to 25°C, and once adventitious roots appear at the submerged part, they can be planted as cuttings. When planting cuttings, a bamboo chopstick should be used to make a hole in the cutting medium to avoid damaging the adventitious roots. Because the base of old oleander stems has a very strong sprouting ability and often sends out large numbers of tender shoots, these branches can be fully used for softwood cuttings in summer. Choose semi-lignified cuttings, keep the top 3 small leaves, and insert them into the substrate; with timely shading and water management, the survival rate is also very high. Water propagation alone can also be used: soak the base of the cuttings in water, maintain a water temperature of about 20°C, change the water frequently, and after rooting, transplant them into a seedbed for care; the results are also very good. Then plant the rooted cuttings in the seedbed for cultivation, but it is best to provide shade.
Oleander is also very easy to propagate by layering. Layering is generally done in the rainy season. In spring, girdle a 1 to 1.5 cm wide strip of bark at a suitable spot on a 2-year-old branch, then bend it down and bury it in another pot of soil. After that, pay attention to watering and keep the pot soil moist. By late summer or early autumn, it can be separated from the mother plant.
When taking oleander cuttings, the following issues need attention:
1. Selection and treatment of the seedbed
As far as possible, choose a plot sheltered from the wind and facing the sun, without standing water, with few soil diseases, pests, and weeds, sufficient fertility, and easy management as the seedbed. Generally the seedbed should run east-west. No matter which method is used for cutting propagation, the soil must be finely prepared. Generally, the depth of cultivation should reach 25-30 cm, the bed width should be 1 m, the length should be suitable, and the path width should be 50 cm. When the soil is sticky and heavy, sand can be mixed in appropriately, and attention should be paid to soil disinfection.
2. Selection and treatment of cuttings
1. Selecting shoots
As mother plants for collecting cuttings, they must have conditions such as excellent quality, vigorous growth, and no pests or diseases. On the same plant, cuttings should generally be chosen from current-year branches on the middle and upper parts facing the sun, with relatively short internodes, thick and strong branches and leaves, and plump buds. On the same branch, for hardwood cuttings, branches from the middle and lower parts are generally used; the cut should be smooth, with the upper end cut flat and the lower end cut at a slant. When cutting branches, choose thick and strong branches with a diameter of 1-1.5 cm; the cutting length should be 15-20 cm, and the cutting must have two or three buds, with the upper cut about 1.5 cm from the bud, and remove the lower leaves. When pruning branches, separate the red- and white-flowered varieties.
2. Treatment of cuttings
Separate the cuttings by flower color and variety, and do the collecting, cutting into lengths, and planting as they are taken. To improve the survival rate of cuttings, when planting, tie dozens of cuttings neatly into bundles, soak the cuttings in 100 ppm ABT Rooting Powder No. 1 for 2-8 hours, or soak them in 30-100 ppm Rooting Powder No. 6 for 1-8 hours. Generally, 1 gram of rooting powder can treat 3000 cuttings.
3. Cutting method and density
Before cutting, the soil should be disinfected and the cutting bed watered thoroughly. Insert the treated cuttings at a row spacing of 5 x 5 cm. Pay attention to the upper and lower ends of the cuttings; they must not be inserted upside down. The cut end of the cutting must be in close contact with the soil, and care must be taken to avoid scraping the cortex at the lower cut end of the cutting. For this reason, first make holes in the cutting bed with an iron rod or similar tool, then insert the cuttings, but the depth of the holes should be slightly shallower than the length of the cuttings so that the cuttings can be inserted into the soil. The cutting depth should generally leave one or two buds above ground, and after cutting, make marks and records.
4. Management after cutting
The temperature required for most flower and tree cuttings to root is 20°C-25°C, with a relative humidity of 80%-85%; generally roots form 15-20 days after cutting. After cutting, water must be sprayed sufficiently so that the soil and cuttings are in close contact. To prevent the midday temperature from being too high, it is best to provide shade. According to soil moisture conditions, spray water once each morning and evening, but the amount of water sprayed must not be too much, otherwise it will affect the healing and rooting of the cuttings. To prevent disease, spray a fungicide solution about once every 10 days. Transplant in the spring of the following year.
Cultivation management
Oleander has strong adaptability and is relatively easy to cultivate and manage; whether planted in the ground or in pots, it is relatively undemanding. 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. The branches and leaves are easily damaged by scale insects, so attention should be paid to control.
Oleander has relatively high fertilizer and water requirements, so more fertilizers such as pig manure and soybean cake should be applied, and it should be watered frequently to keep it semi-moist. At Frost's Descent, move it into a cold cellar to overwinter. At this time, there is no need to fertilize, watering can be reduced, and soil should be mounded around the base to a thickness of 3-4 cm. When the weather warms in April, take it out of the cellar; it blooms from April to July. After flowering, pinch the tips to encourage branching and continued blooming. Oleander can sprout 3-4 times each year and grow more than 30 cm taller. The leaves are poisonous.
For potted oleander, in addition to requiring good drainage, sufficient fertility is also needed. Oleander is a fertilizer-loving plant. For pot cultivation, in addition to applying sufficient base fertilizer, fertilizer should be applied once a month during the growing period. 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 branches that are too dense inside the canopy, part of them should also be thinned out, so that the branches are evenly distributed and the tree shape remains full. After 1-2 years, repot once, and repotting should be done after pruning. Summer is the period of vigorous growth and flowering for oleander, and its water demand is high. In addition to watering once each morning and evening every day, if the pot soil is seen to be too dry, an additional spraying should be given to prevent tender 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, cause the branch tissues to mature, and increase nutrient accumulation, so as to help it overwinter safely. The overwintering temperature needs to be maintained at 8°C-10°C; below 0°C, it will drop its leaves.