A Detailed Guide to Practical Techniques for Cutting Propagation of Japanese Yew (Taxus cuspidata)

Japanese yew, also known as yew, red cypress pine, and vermilion tree, is a tree or large shrub of the Taxaceae family. Its bark is reddish-brown, thin, with shallow fissures. The leaves are arranged irregularly on two sides, slightly sickle-shaped, dark green on the surface, with two gray stomatal bands on the underside. One-year-old branches are smooth and hairless, dark green. It can reach a height of 20 m and a diameter at breast height of 1 m. The crown is ovate, broadly ovate, or triangular-ovate, with densely growing branches. The seeds are purplish-red, ovate, with a fleshy aril. The flowering period is May to June, the fruit ripening period is October, and the lifespan is 200 to 300 years. Young trees prefer shade, and after 7 to 8 years they prefer light. It has strong cold resistance, with no frost damage observed at a low temperature of -45°C. It grows in cold and humid climates, in loose, fertile, well-drained soil, and avoids waterlogging and marshy land. The best growth occurs on slightly acidic slopes with a soil moisture content of 40% to 60%. In nature, it is found in the Changbai Mountains of Jilin at elevations of 500 to 1000 m. Japanese yew is an endangered species protected by international convention and is also a precious ornamental tree for landscaping. It can be planted as a specimen, in pairs, or in groups, can be pruned into various geometric shapes, and can also be used as bonsai and evergreen hedge material. Its roots, stems, leaves, bark, and fruits can all be used medicinally. The leaves can promote menstruation and diuresis, treat high blood pressure, and have effects in suppressing diabetes and treating heart disease. Paclitaxel extracted from yew is a new, highly effective, broad-spectrum anticancer drug, especially effective against ovarian cancer, breast cancer, lung cancer, and leukemia.

China's yew resources are limited in reserve. Since the U.S. FDA officially approved paclitaxel in 1992 as a drug for treating advanced cancer, excessive logging has severely damaged China's wild yew resources. Moreover, yew grows very slowly, and many biological characteristics limit the development of natural populations. According to WHO statistics, the annual number of cancer patients worldwide exceeds 10 million. Even if the world's natural yew resources were completely harvested, it would only meet short-term needs and would also cause irreparable loss to the Earth's environment and biodiversity.

In order to rescue, develop, and utilize this species, we adopted the technical method of clonal cutting propagation. After several years of cultivation research, we have initially mastered the techniques for cutting propagation of Japanese yew seedlings.

1 Preparation of cutting materials

1.1 Cutting shed

To ensure cutting survival, the temperature and humidity of the nursery must be controlled, using the method of plastic greenhouse cultivation. The size of the shed depends on the number of cuttings. Depending on the size of the cuttings, generally 650 to 1300 plants are cut per square meter. When calculating the greenhouse area, in addition to the direct cutting area, auxiliary areas such as paths (walkways), fertilizer yard, and workroom should also be added. It is best to cover the shed more than 10 days before cutting; if cutting in spring, more than 20 days in advance.

1.2 Cutting substrate

Sand, vermiculite, perlite, peat, humus soil, and furnace ash slag were used separately as cutting substrates, with peat giving the best results. The method is: make a cutting bed 1.5 m wide, first spread a 1 to 2 cm thick layer of fine sand on the bed surface, and on the fine sand spread 5 to 15 cm thick crushed decomposed peat soil. This substrate has good permeability and is excellent for both heat retention and water retention.

1.3 Selection of mother trees and preparation of cuttings

1.3.1 Selection of mother trees for cutting collection. Comparing mother trees over 100 years old with those under 25 years old, the cutting survival rates of cuttings taken from the same position were 45% and 85%, respectively. For cuttings collected from the same mother tree, 20-year-old cuttings and cuttings from branches under 8 years old had survival rates of 50% and 95%, respectively, because old mother trees accumulate more rooting inhibitors and have thicker cortex, making it difficult to produce new roots. Moreover, branches of old trees are thin and weak, and even if they survive, their growth is very weak.

1.3.2 Preparation of cuttings. For mother trees under 25 years old, it is sufficient to collect peripheral branches. Cuttings from the middle and lower outer parts of the crown, from 2- to 3-year-old branches, have a high rooting rate. Branches on the shaded side of the mother tree have a higher rooting rate than those on the sunny side, and mother trees in a cutting orchard have a higher rooting rate than wild mother trees.

Generally, cuttings are collected from mother trees in February to March. If they are not cut immediately after collection, they should be stored by the snow-storage method in a frozen place below 0°C, and checked regularly to avoid mold and mouse damage. When using semi-lignified softwood cuttings, they should be cut as soon as they are collected.

2 Cutting

The best time for cutting is when the plant's physiological regenerative capacity is strongest. Cutting propagation experiments have proven that when various conditions of the cutting bed are suitable, rooting can occur in all four seasons, and it is possible to collect cuttings and propagate them at any time.

2.1 Time

Hardwood cuttings from April to early May give the best results. Softwood cuttings are best from early July to early August.

2.2 Method

2.2.1 Cutting of cuttings. Select healthy, pest-free cuttings and cut them into lengths of 7 to 30 cm. The cut cuttings should be bundled in groups of 30 to 50, placed in a windless, shaded place, and sprayed with water frequently to keep them moist.

2.2.2 Effect of hormone treatment on cutting survival. Since 2001, we have collected cuttings from Japanese yew used in landscaping at the nursery of the Jilin City Greening Management Office (1982 seedling yew) and on urban streets in Jilin City, and conducted vegetative propagation at the nursery of Jilin City Tianye Industrial Co., Ltd. Years of experiments have shown that Japanese yew is a plant that roots easily from cuttings. Using indolebutyric acid, naphthaleneacetic acid, indoleacetic acid, ABT2 (rooting powder No. 2), and ABT1 (rooting powder No. 1) in separate experiments, treatment with indolebutyric acid at 100 μg/g began rooting at 45 days and was basically complete at 65 days; ABT2 had a certain inhibitory effect on Japanese yew cuttings; with ABT1 rooting powder, using a 50 μg/g solution to soak the base of the cuttings to 2 cm for 24 hours, with inverted "T" shaped cuttings, the wound healing area was 100%, and the rooting rate reached 98%. After 45 to 60 days, the cuttings began to produce some milky white cylindrical roots around the phloem of the lower cut, at 1 to 3 mm from the lower cut. After about 3 months, the root system reached 3 to 5 cm in length. At the same time, the needles also turned slightly yellow and then deep red, and the terminal buds began to grow, reaching about 2 cm after 3 months of growth. The effect of different concentrations of naphthaleneacetic acid on the rooting rate was extremely significant: 50 μg/g gave a rooting rate of 56%; 100 μg/g gave a rooting rate of 30%; 150 μg/g gave a rooting rate of 27.2%. The differences in rooting rate results for different treatment times with 50 μg/g naphthaleneacetic acid solution were: soaking times of 24 hours, 30 hours, and 40 hours gave rooting rates of 34%, 57%, and 45%, respectively. The results proved that soaking for less than 30 hours was the best soaking time, and once it exceeded 30 hours the rooting rate immediately declined. Experiments proved that using the shoot tips (5 to 7 cm) cut from long branches for cutting Japanese yew is a good method for expanding propagation, saving resources, and effectively utilizing area.

2.2.3 Cutting depth. The cutting depth is about 1/2 of the cutting, that is, for a 10 cm cutting, the part inserted into the substrate is 4 to 5 cm. The plant and row spacing of cuttings can be set at 2.5 to 3 cm, 3 to 3.5 cm, 3.5 to 4 cm, and 4 to 4 cm according to the different specifications of the cuttings. In actual operation, 650 to 1300 plants are cut per square meter.

2.2.4 Temperature and humidity management after cutting. After cutting, the ground temperature at a depth of 5 to 10 cm in the bed should be maintained at 22 to 28°C, the soil water-holding capacity at 60% to 70%, and in the shed a temperature of 18 to 28°C and humidity of 85% are suitable.

2.2.5 Shading. Japanese yew cuttings must be shaded to reduce direct sunlight. For rooting, shading of 60% to 70% is suitable. After survival, gradually remove the shading material.

3 Issues to note

3.1 Light intensity

Japanese yew is a shade-tolerant species, and shading is necessary during cutting to avoid direct light and reduce transpiration. If not shaded after cutting, all non-rooting cuttings will die, and a shading level of 70% gives the highest rooting rate.

3.2 Soil substrate

There are coarse and fine sand beds, and the rooting rate of fine sand beds is 20% lower than that of coarse sand beds.

3.8 Age of source tree and branches

The ability to root from cuttings is related to the age of the source tree and the age of the branch itself. Young mother trees and young branches are rich in meristematic tissue with growth capacity, so after cutting the rooting rate is higher; while new trees and new branches weaken during growth, so the rooting rate is lower.

3.4 Hormone treatment

Young yew trees and young branches have a relatively high rooting capacity, and experiments have proved that they can also root without treatment. Improper hormone treatment can kill the tissue cells of yew and cause the branches to turn black.