A Detailed Guide to Yew Propagation Techniques: Easily Master the Seedling Method
Yew propagation techniques fall mainly into 3 types: sexual propagation, asexual propagation and micro-cutting propagation. Below we explain these three yew propagation techniques in detail.
Sexual Propagation of Yew
In earlier years, the seedling emergence rate of wild yew sown from seed was less than 10%. Scientific research found that its seeds have a dormancy period lasting several years; by using outdoor alternating-temperature storage and applying agents to break seed dormancy, the emergence rate can be raised to above 70%-80%, enabling common yew to break through the barriers of sexual propagation, making large-scale artificial seedling raising and planting possible.
1. Seed collection: From September to October, collect ripe fruit, place it in a basin, add an appropriate amount of coarse sand and water, and rub and wash repeatedly on a wooden board to rub off the outer peel and flesh of the seeds, then rinse repeatedly with clean water until clean and set aside.
2. Seed soaking: Before sowing, first soak in a 1:1 mixture of 50-degree baijiu and 40-degree warm water for 20 minutes, remove, then soak in 500 P P M gibberellin for 24 hours, which can induce the production of hydrolases and promote germination.
3. Sowing: Experiments show that the fresher the seed, the higher the emergence rate. Sowing within one week after seed collection can achieve a germination rate above 90%, while sowing at the Start of Spring gives only 50%, so raise seedlings immediately after collecting seed in September and October. For the seedbed, make it 1.2 m high, with length calculated by seed quantity at 100 sq m of seedbed per kilogram of seed. When turning the soil in the seedbed, apply farmyard manure, with 100 kg of phosphate fertilizer and 30 kg of nitrogen fertilizer per mu. Use 2 kg of powdered insecticide to kill underground pests, then open drainage channels and set aside. Dry the surface water of the soaked seeds, add an appropriate amount of fine sand to facilitate broadcasting, evenly broadcast at 5 kg per mu onto the seedbed, water thoroughly with clean water, then cover with the prepared fine soil at a thickness of about 1 cm.
4. Seedling care: After sowing, cover the seedbed flat with plastic film; after the Start of Spring, change the flat film to an arched film and begin raising the temperature to force germination, checking temperature and humidity at any time; if the temperature is too high, uncover one side of the agricultural film to cool it down. After germination begins, water the seedlings about once every 4 days. When the small seedlings have two leaves and one heart, remove the film to harden the seedlings and thin and space them out; when the small seedlings grow to 5 cm tall, even out the seedlings in dense areas, maintaining a basic stand of twenty thousand plants per mu, and heel in the thinned seedlings in other plots at a spacing of 15×20 cm. Weeding and topdressing during the seedling stage: weeds often grow in the nursery, which can be pulled by hand or removed along with loosening the soil; after each loosening, topdress with 10 kg of urea per mu, 5 kg of potassium chloride and decomposed farmyard manure. During the seedling stage, topdressing is needed three times to ensure strong seedlings. During the seedling stage, spiders, aphids, cabbage caterpillars and the like may appear, which can be controlled by spraying dichlorvos, dimethoate and similar insecticides. After the seedling grown from seed has grown in the seedbed for one year, when the seedling height is above 30 cm and the stem diameter is 0.3 cm, it can leave the nursery for afforestation.
Asexual Propagation of Yew
Asexual propagation is mainly cutting propagation. Taxus media (Man Di Ya yew) is a hybrid variety; to maintain variety purity, it is generally limited to asexual propagation.
1. Timing. In spring it can be done from February to April, and in autumn from September to November. During this time the temperature is generally above 15°C and below 25°C, ensuring that the cuttings lose less water through evaporation and that the roots heal.
2. Cuttings. For cutting propagation, the scion shoots must first be pest- and disease-free, vigorous branches, 0.3 to 0.8 cm thick and 10 to 15 cm long. After cutting, first remove the lower 1/3 of the leaves, place them in rooting solution to soak for two hours, then insert them into the seedbed promptly.
3. Seedbed. If conditions permit, make the seedbed in a greenhouse, and the substrate can use perlite and vermiculite. For small-scale propagation, sandy soil with 1/3 humus soil added can be used. The seedbed can be made 1.2 m wide, with length depending on the seedling raising, and the substrate portion about 20 cm thick. First irrigate to firm the substrate, then carry out cutting.
4. Cutting. Insert the prepared cuttings into the seedbed at a plant spacing of 4 cm and a row spacing of 10 cm, with 1/3 of each cutting inserted into the soil.
5. Management. Spring cuttings generally take 30 days to root, and autumn cuttings generally root only the following year, so seedbed management is key to cutting survival. After insertion, irrigate promptly. On the seedbed, use bamboo strips to arch a frame 15 cm above the ground, lay plastic film flat over the frame; for spring cuttings, remove the film after April and cover with a shade net; for autumn cuttings, the film must remain covered until April of the following year, and when the temperature is high, also switch to a shade net. The film is mainly used to maintain humidity in the seedbed, and in winter it can also increase the seedbed temperature. A shade net with a 80% shading rate generally gives better results. For large-scale propagation, the shade net should be set up about 2 m above the ground; for small quantities, covering the seedbed is enough. After insertion, if the leaves remain green and neither wither nor yellow, this indicates normal management. After 20 days, pull one out to check whether the cut at the base of the cutting shows signs of healing and whether cell tissue is growing; this is an important sign before rooting.
Spring cuttings root after the cell tissue increases. For autumn cuttings, after this cell tissue increases, as the temperature drops, they must wait until after February of the following year when the temperature rises before continuing to grow from the original cell tissue to form new roots. However, this tumor-like tissue also has the function of absorbing water and nutrients, and can maintain the cutting's own water needs. After new roots grow out, fertilizer can be topdressed, with 20 jin of urea and 5 kg of compound fertilizer per mu of seedbed applied by watering; before leaving the nursery, topdressing can be done 2 times, and the fertilizer amount can be determined according to seedling condition. Foliar fertilizer can be applied after 10 days, generally spraying once every 20 days; in the early stage it can promote root healing, and after rooting it can promote root growth and the growth of upper small branches. During the seedling stage, weeds in the seedbed must be removed frequently to avoid competing with the seedlings for water and nutrients. Spring cuttings basically have well-developed roots after September of the same year, reaching about 20 roots, with roots about 15 cm long, and 3 to 5 new branches on the upper part, more than 10 cm long. Autumn cuttings begin to grow roots after February of the following year, and after June can be heeled in or transplanted (too high a temperature in June and July makes transplanting unsuitable), or can continue to remain in the seedbed for management, and after September can be transplanted. Autumn cuttings have a longer growth period and grow better than cuttings from the same year. No matter which cutting method is used, as long as management is done well, the survival rate can reach above 90%, making it the main propagation method currently used to develop Taxus media.
Micro-cutting Propagation Method for Yew
The micro-cutting propagation method is also called the “non-test-tube tissue culture method”. Its feature is that it can increase the propagation multiple of limited material, and it is used when the number of mother trees is small; moreover, propagation cost is low and propagation volume is large. The disadvantage is that the seedling stage must be extended by 1 year before transplanting, and after rooting it needs 1 year of heeling in to meet the requirements for leaving the nursery. The propagation technique is relatively demanding, and it can only be used with a certain technical foundation and production conditions. Cover with a shade net on top, keep the seedbed moist at all times, and strictly prohibit direct sunlight. As long as the leaves do not yellow or wither and remain green, this indicates normal growth. After about 20 days, check whether the cut at the base of the cutting has healed and whether cell tissue is growing; this is the main state before rooting. During this period, foliar nutrient fertilizer can be topdressed. After 40 days, check that new roots have grown, and nitrogen fertilizer can be applied by watering with water. At most twice during the seedling stage. Generally, spring cuttings are transplanted in autumn, and autumn cuttings are transplanted before June of the 2nd year or in September. The standard for transplantable seedlings is reaching more than 20 fibrous roots, with root length 10 cm and generally about 3 new branches on the upper part, 5—10 cm long.