White ash (scientific name: Fraxinus chinensis Roxb), a deciduous tree of the Oleaceae family, has grayish-brown bark with vertical fissures. The buds are broadly ovate or conical, covered with brown soft hairs or glandular hairs. The branchlets are yellowish-brown, rough, hairless or sparsely covered with long soft hairs, soon becoming smooth, with small, inconspicuous lenticels. The terminal leaflet is nearly equal to or slightly larger than the lateral leaflets, with a sharp to acuminate apex, a bluntly rounded or wedge-shaped base, and evenly serrate leaf margins; the upper surface is hairless, the lower surface is hairless or sometimes covered with white long soft hairs along both sides of the midvein, and the midvein is flat on the upper surface. The persistent calyx is closely appressed to the base of the
nut, often deeply cleft on one side. The
flowering period is April-May, and the
fruiting period is July-September.
White ash is mostly cultivated, with a long cultivation history in China and a very wide distribution. It is also found in mixed mountain forests at an altitude of 800-1600 m. The plant has strong sprouting ability, straight grain, rapid growth, and is soft and tough, used for weaving various utensils; the bark is also used medicinally.
Propagation Methods
Seed collection: White ash flowers in April-May and matures in September-October. Select superior plants that grow vigorously and are free of pests and diseases, and pick the samaras when they turn from green to yellowish-brown and the seed kernel becomes hard. The seeds do not fall after maturity, so the fruiting branches can be cut off, sun-dried to remove the wings, and cleared of debris; then the seeds are placed in containers and stored indoors in a disinfected, low-temperature, dry, and ventilated room.
Seed treatment: White ash seeds have a long dormancy period, so spring sowing must be preceded by pre-germination treatment. The methods of pre-germination treatment include low-temperature stratification and rapid high-temperature pre-germination.
Sowing and seedling raising: Spring sowing should be early, generally from late February to early March. Drill in furrows, using 3-4 kg of seed per 667 sq m, at a depth of 4 cm, with even depth; open the furrow, sow, and cover with soil as you proceed, with a soil cover thickness of 2-3 cm. To make the soil and seed closely contact, press down after covering with soil.
Cutting propagation: Carry out from late March to early [month] in spring. Before cutting, prepare the land carefully and apply enough base fertilizer so that the soil is loose and has sufficient moisture. Select 1-year-old sprout branches from vigorous young mother trees that grow rapidly and are free of pests and diseases; generally the branch thickness is more than 1 cm and the length is 15-20 cm, with a flat cut at the upper end and a horseshoe-shaped cut at the lower end. Insert 2-3 cuttings per hole, spread them apart, with a row spacing of 40 cm and a plant spacing of 20 cm. Spring cuttings should be buried deep, firm, and with little exposed top; insert 4000 plants per 667 sq m.
tending and management:
1. Irrigation: During the seed germination period, the seedbed surface should be kept moist, and irrigation should be done in small amounts but frequently; after the seedlings emerge completely and the cotyledons fully unfold, they enter the vigorous growth period, when irrigation should be greater in amount and less frequent, once every 2-3 days, each time watering thoroughly and sufficiently. Irrigation is best done in the morning and evening. Drain promptly during the rainy autumn.
2. Loosening the soil: Following the principle of "remove early, remove small, remove completely," pull out weeds after rain or irrigation; loosen the soil when the seedlings enter the peak growth period, shallow at first and slightly deeper later, as long as the seedling root system is not damaged. During the seedling hardening period, to promote lignification of the seedlings, stop loosening the soil and weeding.
3. Topdressing: Apply chemical fertilizer as a supplement during the vigorous growth period of the seedlings. Apply nitrogen fertilizer at the seedling stage; during the rapid growth period of the seedlings, apply more nitrogen fertilizer, potassium fertilizer, or a combination of several fertilizers; in the late growth period, stop applying nitrogen fertilizer and apply more potassium fertilizer. Topdressing should mainly use quick-acting fertilizers, in small amounts but frequently.
Cultivation Techniques
Planting
White ash can be planted in both spring and autumn. Spring planting is advocated as more suitable, but spring planting also requires choosing the best time. For white ash in spring, late planting is also suitable, with mid-April being preferable, that is, when the sap of the seedlings has already begun to flow and most buds on the branches have begun to swell into small spheres, the survival rate of planting is highest. When planting, first dig the tree hole; the size of the tree hole depends on the diameter at breast height of the sapling. Generally, the diameter of the tree hole should not be less than 15 times the diameter at breast height of the sapling, and the depth of the tree hole should not be less than 3/4 of the tree hole diameter. A tree hole that is too small is not conducive to root growth and also makes the tree prone to wind damage. If the soil does not meet the requirements, replace it with foreign soil. First fill in the subsoil and firm it; the base fertilizer should be thoroughly mixed with the backfill soil. Place the sapling in the tree hole and straighten it, check whether any roots are exposed or not smoothly arranged, and after adjusting, fill soil in 2 stages and firm it layer by layer. If it is a small bare-root seedling, after filling the soil, gently lift the seedling so that the roots spread out. When planting, attention should be paid to the planting depth of the sapling. If the planting site conditions are good and the soil is relatively moist, the planting depth can be slightly 2-3 cm above the original soil mark; if the soil at the planting site is dry and not easy to water, it can be buried 8-10 cm deeper. Depending on the size of the sapling, if support is needed after planting, a support frame should also be set up immediately to prevent wind and human shaking. In addition, it is particularly emphasized that when transplanting white ash with a diameter at breast height of more than 8 cm or full-crown white ash trees, planting with a soil ball is advocated, as this can greatly improve the survival rate of the saplings.
Water and Fertilizer
After planting, water the first 3 times in time as required, especially the 1st watering, which should be thorough and firm; water the 2nd time again after 4-5 days, and then water the 3rd time according to conditions. In the year of planting, keep the soil moist as much as possible to help the saplings recover their growth as soon as possible. In late autumn, water thoroughly for freeze protection; in early spring of the 2nd year, water well for green-up. April-May is the spring drought period, and in northern China spring winds are strong, rain is scarce, and the period lasts a long time, so water 1-2 times. White ash is a water-loving tree species; where conditions permit, watering lightly 1-2 more times in June-July is even better, so that the white ash has sufficient water supply and thus maintains the saplings in a vigorous growth state. In the 3rd and 4th years, manage in the same way. The number of waterings should be flexibly controlled according to weather conditions. White ash tolerates poor soil; although it is not strict about soil fertility, it must still meet the nutrients required for normal growth and development of the saplings. In addition to applying enough decomposed and fermented barnyard manure in advance to newly planted saplings, apply 1 topdressing of nitrogen-phosphorus-potassium compound fertilizer to the saplings after mid-to-late June; where conditions permit, applying cow or horse manure once more in late autumn together with the freeze water is even better. In the following spring, apply 1 topdressing of nitrogen-phosphorus-potassium compound fertilizer, and in late autumn apply 1 additional farmyard manure; for later management, only additional farmyard manure in late autumn is needed. Sufficient fertility can not only accelerate the growth rate of the saplings, but also enhance their stress resistance, especially improving their resistance to pests and diseases.
Pruning
Pruning and shaping are a very important technical link in bringing saplings to standardized management, and are easily overlooked. First, pruning the root system before planting the sapling is crucial. The main task is to cut back damaged roots so that the root wounds are smooth and facilitate the formation of callus tissue, while also preventing root rot. In addition, the sapling needs trunk truncation before planting, which can be flexibly controlled according to the size of the sapling and project needs; generally, the trunk is headed at a height of 2.8-4 m, and after sprouting, it can be allowed to grow freely. During pruning in early winter, select 3-5 evenly distributed and vigorously growing branches on the trunk as main branches, remove all other lateral branches below the branching point, note that the cut should be flat, and shorten the retained main branches by retaining a length of 40-50 cm. The next year, 2-3 lateral branches can be retained on each main branch, and all other lateral branches should be removed; the retained lateral branches must be strong in growth. This ensures a full crown and also ensures ventilation and light transmission, reducing the occurrence of dead branches and the incidence of pests and diseases. After the basic trunk framework is formed, in subsequent years only dense branches, dead branches, pest- and disease-damaged branches, and drooping branches need to be removed.