Detailed Explanation of Eucommia Seed Propagation and Cultivation Techniques

Eucommia (Eucommia ulmoides) is a plant of the family Eucommiaceae, also known as simianpi and siliampi, and has functions such as tonifying the liver and kidneys, strengthening bones and muscles, calming the fetus, and lowering blood pressure. It originated in China and has a cultivation history of nearly a thousand years. The growth rate of Eucommia is relatively slow in the early stage, and the rapid growth period appears at 10-20 years; from 20-35 years, the growth rate of the tree gradually slows, and thereafter it almost stagnates. The growth process of the bark is almost consistent with tree height, and bark yield varies with tree age and is also affected by environmental conditions. Eucommia is light-loving and has no strict requirements for soil and temperature; it can safely overwinter at -20°C. However, it grows and develops faster in humid and relatively warm areas. The seeds have a certain degree of dormancy; after 50-70 d of low-temperature stratification at 8-10°C, the germination rate can reach about 90%. The seed lifespan is relatively short, generally not exceeding 1 year, and after drying it more easily loses germination ability, so after seed collection it is advisable to sow immediately.

1 Nursery site selection

Select a plot with loose, moist, fertile soil and good drainage. Before raising seedlings, deeply plow and finely till the nursery land, remove weeds, and apply sufficient base fertilizer, applying cake fertilizer at 2 250-3 000 kg/hm2. At the same time, apply slaked lime at 150-225 kg/hm2 to disinfect the soil and kill underground pests. Then finely level the land and make fine beds 1 m wide.

2 Sowing

Propagation can be carried out by seeds, cuttings, layering, and grafting, with seed propagation being the main method in production. When collecting seeds, select trees over 15 years old growing on fertile soil in sunny locations as mother trees, and sow seeds that matured in the current year, are fresh, plump, yellow-brown, and glossy, in winter from November to December or from February to March when the monthly average temperature reaches above 10°C. Generally, warm areas should sow in winter, while cold areas can sow in autumn or spring, so as to meet the low-temperature conditions required for seed germination. Seeds should not be dried, so it is advisable to sow while fresh. If spring sowing is needed, the seeds should be stratified after collection, with a seed-to-wet-sand ratio of 1:10, or before sowing the seeds should be placed in 60°C water, allowed to cool naturally, kept at 20°C, and soaked for 2-3 d, changing the water 1-2 times per day. When the seeds swell and the seed coat softens, take them out, dry them slightly, mix them with plant ash and dry soil, and sow after mixing evenly. For drilling, the row spacing is 20-25 cm, and the seeding rate is 120-150 kg/hm2. After sowing, cover with grass and water thoroughly to keep the soil moist and facilitate seed germination. After the seedlings emerge, remove the covering grass on cloudy days, and 450 000-600 000 seedlings per hm2 can be produced.

3 Nursery management

3.1 Thinning seedlings Thin out seedlings that emerge too densely for transplanting elsewhere, keeping a plant spacing of 8-10 cm. It is best to transplant after the seedlings have basically emerged completely but before true leaves open, because before true leaves open the roots are almost without fibrous roots. On cloudy days or in the evening, gently pick them out with a hard bamboo strip (keeping as much soil as possible), transplant immediately after picking, water after planting, and after 7-10 d apply a very dilute human urine and feces or urea spot fertilizer once.

3.2 Weeding and loosening soil After the seedlings emerge, pull weeds as soon as they appear to prevent weed infestation; after 4 true leaves, loosen the soil and hoe weeds. Early hoeing can raise soil temperature and resist disease sources. The first 1-2 times should be shallow loosening; throughout the seedling stage, loosen the soil and hoe weeds 4 times. During the high-temperature period in August, only pull weeds without loosening the soil. It can also be combined with deep plowing of the land for forest-grain intercropping, using cultivation instead of tending.

3.3 Fertilization Fertilization at the seedling stage should be “small meals but more often,” preferably with farmyard manure and compound fertilizer. Fertilization should be light, preferably by dilute watering after each soil loosening. Ammonium bicarbonate should not be used to prevent fertilizer damage. After the seedlings are 30 cm tall, urea can be broadcast on rainy days, with each application at 60-75 kg/hm2. After the seedlings are 40 cm tall, urea can be lightly broadcast once every 15-20 d. Eucommia seedlings grow rapidly in autumn; if fertilizer keeps up, the larger ones can grow 1.0-1.1 m tall in the same year, thus producing high-quality seedlings. For topdressing, nitrogen fertilizer at 120-180 kg/hm2, phosphate fertilizer at 120-180 kg/hm2, and potassium fertilizer at 60-90 kg/hm2 can be used, or 25 kg of farmyard manure per plant, with ring-shaped furrows 15-18 cm deep, and soil covered after fertilization.

4 Field planting

When 1- to 2-year-old seedlings reach more than 1 m in height, they can be field planted after leaf fall or in the following spring. The plant and row spacing is 1.5 m × 2.0 m, the hole diameter is 70 cm, and the depth is 70 cm. Lift seedlings and transplant at the same time. In the year of transplanting, generally cultivate 3-4 times and combine with fertilization. Apply farmyard manure once before spring sprouting and once after leaf fall, and topdress with high-quality stable manure at 30.0-37.5 t/hm2. In northern regions, stop fertilization in August to avoid excessive late growth that reduces cold resistance.

5 Pest and disease control

The main pests and diseases include damping-off, root rot, leaf blight, and leopard moth. For damping-off control, during land preparation scatter ferrous sulfate powder at 105-150 kg/hm2 or spray 40% formaldehyde solution at 45 kg/hm2, then cover with grass for soil disinfection; when sowing, mix 50% carbendazim at 37.5 kg/hm2 with fine soil and scatter it on the seedbed or in the sowing furrow; in the early stage of disease, irrigate with 1 000-fold 50% carbendazim solution. In cultivated land with a high groundwater table or poor drainage, Eucommia is prone to root rot and the whole plant dies, so drainage should be strengthened; at the same time, dig out diseased trees and burn them, and disinfect the tree holes with 50% formalin. Leaf blight damages leaves and in severe cases causes leaves to die, so the nursery should be kept clean, and during the growing season spray 1:1:100 Bordeaux mixture for control. For leopard moth control, clean the field in winter; in early June, before adults lay eggs, brush the trunk with whitewash; during the larval hatching period, spray 40% dimethoate emulsion at 400-800 times on the trunk.

6 Harvesting and processing

Eucommia can begin to be peeled only after more than 10-15 years of planting, and peeling is carried out from April to June. Use a saw to cut a ring-shaped incision flush with the ground, deep to the xylem, and cut a second ring-shaped incision 80 cm above. Make a longitudinal cut between the two ring incisions, and gently peel at the cut to separate the bark from the xylem. After harvesting, scald the bark with boiling water, flatten it, place the inner surfaces facing each other in pairs, press tightly layer by layer, surround top and bottom with grass, and let it sweat. After about 7 d, the inner bark turns dark purplish-brown; take it out, dry it in the sun, and scrape off the rough outer bark.