Detailed Explanation of Key Techniques for Container Seedling Cultivation of Yew

The yew (Taxus) is an evergreen tree of the genus Taxus in the family Taxaceae, a national Class I key protected plant, a relict species from after the Quaternary glaciation, known as a "living fossil" of the plant kingdom and a rare and endangered plant worldwide; it is not only an important timber tree species and ornamental tree species, but also a precious medicinal plant. The branches, leaves, roots and bark can be used to extract the anti-cancer drug paclitaxel, giving it great value for promotion and utilization.

Yew can be propagated by cuttings or by seeds. Due to uneven resource distribution and difficulty in collecting scions, seed propagation is mostly used. Bare-root yew seedlings raised by conventional seedling cultivation have a relatively low survival rate after afforestation. To solve this problem, after several years of trials, container seedling cultivation has been summarized: the yew seedlings raised have a high afforestation survival rate (up to 95%), a long planting period, low cost, high benefit, simple operation, and are suitable for promotion.

1 Selection of seedling cultivation site

Choose a site close to the afforestation area, with flat terrain, convenient transportation, sufficient water source and easy management as the seedling cultivation site. Plots whose previous crops were vegetables, melons and fruits, tubers or corn should not be selected.

2 Land preparation and bed making

Use raised-bed seedling cultivation. The bed surface is 10 m long, 1.2 m wide and 20 cm high, with a walkway 40 cm wide. The bed surface should be leveled and compacted. The bed orientation should preferably be north-south. Dig drainage ditches around the seedling cultivation site so that internal water does not accumulate and external water does not flood.

3 Seedling substrate

A substrate made by mixing 70% forest humus soil and 30% loess (or turf soil) is relatively ideal. To increase substrate fertility, add 5 kg of superphosphate and 2 kg of urea per cubic meter of substrate. To prevent seedling diseases and insect pests, use 5 kg of ferrous sulfate per cubic meter of substrate for soil disinfection, and 20 g of phoxim can kill various pests.

4 Container filling and placement

For cultivating 2-year-old yew container seedlings, choose 7 cm x 12 cm bottomed container bags with holes. Before filling the substrate, thoroughly stir and mix the various ingredients and sprinkle an appropriate amount of water; the substrate moisture content should be 10%-15%. The container bags must be filled firmly, filling to 1 cm below the upper rim of the container. After the containers are filled with soil, they should be placed neatly and uniformly in the seedling bed. The containers should be pressed tightly against each other, and soil should be banked around the seedling bed to prevent the containers from collapsing.

5 Seed treatment

5.1 Seed collection

Collect red fruits from September to October, rub off the red false fruit skin and pulp, wash clean, soak the seeds in 0.5% potassium permanganate solution for 2 hours, and store mixed with moist sand.

5.2 Breaking the seed coat

Repeatedly rub the seeds with a shoe sole or waste tire on rough cement ground to wear the hard seed coat thin (never rub the seed kernel to pieces), so that the seeds are more permeable to water and air and germinate faster when sown.

5.3 Variable temperature treatment

The seeds have a relatively long after-ripening period, and the radicle and plumule have double dormancy characteristics. Under natural conditions, they can only germinate after 2 winters and 1 summer. The radicle needs about 1 month at a high temperature stage above 25 degrees C to break dormancy, and the plumule needs about 1 month at a low temperature of -3 degrees C to -20 degrees C to release dormancy. To promote seed germination, mix yew seeds with broken seed coats with moist sand, place them in a natural environment below -3 degrees C in the depth of winter for freezing for 25-40 days to release plumule dormancy; in early March, keep the seeds mixed with moist sand at suitable humidity, sprinkle water at night and mix evenly in a pile, spread them out evenly during the day without sprinkling water, and turn them frequently so that the seeds are heated evenly. With artificial heating to above 25 degrees C, after 30-40 days, radicle dormancy can be broken.

5.4 Accelerating germination

Begin accelerating germination in early April. Soak the seeds with the sand sifted out in 0.5% potassium permanganate solution for 2 hours. Control the indoor temperature at about 25 degrees C and the relative air humidity at 80%. Keep an appropriate amount of moisture on the seed surface, preferably so that moisture can be seen but no water is visible. Keep the room ventilated until the seeds show white.

6 Sowing

Spring sowing is the main method, and earlier is better than later. From late April to early May, when the air temperature rises above 15 degrees C, sow by dibbling. Select seeds showing white from the germinating seeds for dibbling. Sow 2 seeds per container bag and cover with 1-1.5 cm of soil. After covering with soil, spray 0.1% potassium permanganate or 1% ferrous sulfate solution at a rate of 2-3 kg per square meter, then spray clean water once again half an hour later (the amount of chemical used is the same as the amount of water). This not only disinfects the covering soil, but also brings the seeds into close contact with the soil, which is beneficial for seed germination. Finally, cover with a shade net 30 cm above the bed surface to keep the bed surface shaded and moist.

7 Seedling stage management

7.1 Control of birds, animals, diseases and insect pests

The seedlings emerge with the seed coat, and it takes about 20 days for the seed coat to fall off by itself. During this period, attention should be paid to preventing birds from damaging the seedlings when pecking at the seed coat, especially strengthening manual guarding every morning and evening. To prevent mice from stealing seeds, poison bait can be placed on the bed surface or walkways. The seedling emergence period is a period when diseases and insect pests occur frequently, mainly preventing yew seedling damping-off and seedling blight. Starting from seedling emergence, spray alternately with 0.2% potassium permanganate and 1% ferrous sulfate solution every 7 days to prevent diseases, and rinse the seedlings with clean water after spraying. Once disease occurs, spray the bed surface with 2%-3% ferrous sulfate aqueous solution or 1% potassium permanganate solution, and rinse the seedlings with clean water half an hour before and after spraying to prevent chemical injury. At the same time, thoroughly remove diseased seedlings. A shade net can be used to prevent seedlings from being scorched by sunlight.

7.2 Management of water, fertilizer and weeds

Before emergence and during the seedling growth period, keep the substrate surface moist regularly to ensure the water needed for seedling growth. Watering should be appropriate, using the method of spraying a small amount many times, which can both lower the surface temperature and regulate the relative humidity around the seedlings. Never sprinkle water at noon during high temperatures. In the late stage of seedling growth, watering should be controlled. Water once before overwintering to improve the cold resistance of the seedlings.

Topdressing is an important measure to supplement seedling nutrients, improve substrate nutrition and promote rapid seedling growth. Yew seedlings begin topdressing from the appearance of primary leaves and entry into the rapid growth period. Topdressing should be combined with spraying water to prevent fertilizer injury. In June, mainly apply nitrogen fertilizer, applying 1% urea once every half month for 2 applications; in July, mainly apply potassium fertilizer, applying 0.2% potassium dihydrogen phosphate once every half month for 2 applications; in August, seedlings enter the late growth stage and fertilization should be stopped to promote full lignification of the seedlings and facilitate safe overwintering.

During the seedling stage, weeds should be removed in time, adhering to the principle of "remove early, remove well, remove completely", so that there are no weeds in the containers, on the bed surface or in the walkways. When weeding, prevent loosening the seedling roots.

8 Transplanting and planting

2-year-old seedlings are transplanted with nutrient soil. Water thoroughly once 1 day before lifting seedlings so that the container seedlings absorb enough water. During seedling lifting, transport and planting, handle lightly and place lightly so that the soil ball in the container bag remains intact, avoiding loosening the seedling roots and ensuring the afforestation survival rate. When transplanting, cut open the bottom of the container bag to facilitate rooting of the seedlings, and the container mouth should be level with the ground. The transplanting density can be determined according to the direction of seedling cultivation and utilization. In the 5 years after transplanting, loosen the soil and remove weeds twice each year, and fertilize once each year, applying 0.1 kg each of urea and superphosphate per plant to promote the growth of young trees.