A Detailed Guide to the Planting Techniques and Cultivation Management Methods of the Tree of Heaven (Ailanthus altissima)
The tree of heaven, also known as Ailanthus bark, big-fruit ailanthus, and other names, is a tree plant of the genus Ailanthus in the family Simaroubaceae. Its trunk is straight and tall, and its crown is round and neat like a hemisphere, quite spectacular. Its leaves are large and its shade is dense, and in autumn the whole tree is full of red fruits. Although the leaves and flowers have a slight odor when they bloom, it is not serious, so it is still a very good ornamental tree and shade tree. Let us take a look at the planting techniques for the tree of heaven below!
Ecological Habits of the Tree of Heaven
The tree of heaven likes light and does not tolerate shade. It has strong adaptability. Except for clay, it can grow in all kinds of soil and in neutral, acidic and alkaline soils. It is suitable for growing in deep, fertile and moist sandy soil. It is cold-resistant, drought-resistant, and not resistant to waterlogging. Long-term water accumulation will cause root rot and death. It is a deep-rooted species and has strong resistance to smoke, dust and sulfur dioxide, with relatively few pests and diseases. In China, it is distributed in all areas except Heilongjiang, Jilin, **, Qinghai, Ningxia, Gansu and Hainan, and it is widely cultivated around the world.
Propagation Techniques for the Tree of Heaven
The tree of heaven is generally propagated by sowing. When the samaras mature, cut them off together with small twigs, dry them in the sun, remove impurities, and store them dry. The germination capacity can be maintained for 2 years. Before sowing, soak the seeds in 40°C warm water for a day and a night, which can advance germination by 5-6 days. The sowing rate is 5-8 kg per mu, with row sowing at a row spacing of 25-40 cm, covered with 1-1.5 cm of soil, and the germination rate can reach 85%. The suitable temperature for seed germination is 9-15°C, and sowing is generally carried out from early March to late April. One-year-old seedlings reach 60-100 cm in height, with a ground-level diameter of 0.5-1.5 cm. In addition, it can also be propagated by suckers and root cuttings. For large seedlings used as street trees, the trunk is required to be straight and the branching point high. Generally, stumping can be carried out in the spring of the second year of seedling cultivation, and afterwards side buds should be removed in time so that the trunk continues to extend. After reaching the trunk-setting height, side branches are then allowed to develop to form the crown. Spring transplanting should be carried out when the strong buds on the upper part of the seedling swell into a spherical shape, and it should be planted appropriately deep.
Planting Techniques for the Tree of Heaven
1. Seedling afforestation: Planting can be done in both spring and autumn. The key is to grasp the suitable timing and deep planting. For spring afforestation, it is best to plant early, when the strong buds on the upper part of the seedling stem enlarge and become spherical. The planting depth should preferably exceed the root collar by 2-3 cm. On hillsides, level ditches or fish-scale pits can be used for land preparation. In areas without uneven terrain, hole-shaped land preparation is mostly used. The planting density should not be too large. The common plant and row spacing is 1×2 m. The root holes are 40 cm in length, width and depth. In dry and windy places, truncation afforestation is suitable. In early spring, bury to a depth exceeding the root collar by 15-18 cm, with the upper end level with the soil surface or exposed 1 cm above the surface.
2. Direct seeding afforestation: For direct seeding afforestation, site selection on shady slopes and semi-shady slopes gives a high survival rate. Afforestation is carried out in the three seasons of spring, the rainy season and autumn. Spring sowing generally emerges in the rainy season, and seeds that have not undergone pre-germination treatment are likely to survive. For spring sowing, seedlings emerge in the rainy season. Although the aboveground parts may wither in winter, in the following spring strong shoots can still sprout from the root collar. For reverse-slope fish-scale pits, a ditch is opened near the outer edge parallel to the outer edge. In the inner-ditch outer-platform method, a ditch is opened on the outer platform for sowing. The ditch is 5-6 cm wide and 3 cm deep, with 40-50 seeds sown per ditch, covered with 1.5-2.0 cm of soil, lightly compacted, and the sowing rate is 0.5 kg per mu.
3. Tending and management: After afforestation of the tree of heaven, stumping is carried out once each autumn or spring within 1-2 years. In that year the tree height can reach 2-3 m. In April-May, select and retain one strong sprout, and carry out bud removal and tending year after year. When the tree height reaches the required height, stop removing buds, so that height growth gradually weakens and diameter growth at breast height is promoted. In the third year of direct seeding afforestation, the young trees derived from the trees compete for light, nutrients and so on. To ensure the rapid growth of superior plants, weak seedlings must be removed as early as possible. Generally, where site conditions are good, seedlings grow quickly, so thinning should be done early and with greater intensity; conversely, thinning should be done later and with less intensity.
4. Pest and Disease Control
① Ailanthus silkworm: In winter and spring, look for cocoons on treetops and trunks to destroy the pupae. Inspect the insect feces under the trees and the damage symptoms on the trees. When larvae are found, shake the branches manually to knock them down and kill them. During the larval stage, spraying can be used for control with 20% fenpropathrin emulsifiable concentrate at 2000 times dilution, 2.5% beta-cypermethrin emulsifiable concentrate at 2000 times dilution, 2.5% deltamethrin emulsifiable concentrate at 2000 times dilution, etc. Use light traps to kill adults.
② Spotted lanternfly: In cold winter, scrape off the egg masses on the trunks. In pure forests with severe damage, build mixed forests. Protect and utilize natural enemies such as parasitic wasps of the insects. For adults and nymphs, spray with 20% phosphamidon emulsifiable concentrate at 1500-2000 times dilution, or 50% monocrotophos water-soluble agent at 2000-3000 times dilution, or 50% phoxim emulsion at 2000 times dilution, or 40% dimethoate emulsifiable concentrate at 1500-2000 times dilution.