A Detailed Guide to the Latest Planting Techniques and Methods for Sophora japonica

Sophora japonica is also known as the Chinese scholar tree, huai rui, bean huai, white huai, etc. It is a tree of the genus Sophora in the Fabaceae family, native to China and now widely cultivated in all provinces and regions across the north and south, especially common in North China and the Loess Plateau. It is also distributed in Japan and Vietnam, grows wild in Korea, and has been introduced in countries across Europe and the Americas. It has very high planting value. Now let us take a look together at the planting techniques for Sophora japonica!

The Growing Environment of Sophora japonica

Sophora japonica likes light and is slightly shade-tolerant. It can adapt to relatively cold climates. Its roots are deep and well developed. It is not strict about soil and can grow normally in acidic to calcareous and mildly saline-alkaline soil, even under conditions with a salt content of around 0.15%. It is wind-resistant and also tolerates drought and poor, thin soil, and is especially able to adapt to adverse urban environmental conditions such as compacted soil, but it grows poorly in low-lying waterlogged places. It has strong resistance to pollution such as sulfur dioxide and smoke and dust. It grows relatively fast when young, then grows at a medium rate later, and has a very long lifespan. Old trees easily become hollow, but the latent buds have a long lifespan, which is favorable for crown renewal.

Root Burial Propagation of Sophora japonica

1. Seed root preparation: After the Chinese scholar tree sheds its leaves, the seed roots can be introduced. Before planting, store them buried in sandy soil. Control the moisture of the sandy soil well: the root segments must not be allowed to dehydrate and dry out, nor should the humidity be too heavy and cause mold and rot.

2. Land preparation: For raising seedlings, it is best to choose sandy loam with deep soil, flat terrain, convenient irrigation and drainage, and no sources of pest and disease infection. Apply 2500 kg of livestock and poultry manure per 667 sq m, or apply 50 kg of phosphate fertilizer and diammonium as base fertilizer, and use insecticides such as carbofuran to kill underground pests. The land should be deeply plowed, finely prepared, and raked level, with beds about 1 m wide.

3. Seedling raising: The seedling raising time is early to mid-March in the south, and late March to early April in the north. Choose smooth root segments 1 to 2 years old, 5 to 10 mm in diameter, with no traces of pests or diseases, and cut them into 5 to 7 cm lengths for later use. Open furrows along the bed, with a furrow spacing of 50 cm and a depth of 5 cm, then place the root segments flat in the furrows at a plant spacing of 30 cm, cover with fine sandy soil, water thoroughly to settle the roots, cover well with plastic film, and seedlings will emerge in about one month.

Cuttage Propagation of Sophora japonica

1. Cutting time: The cutting time is the same as for root burial seedling raising, and can also be slightly earlier.

2. Cutting selection: Select lignified hard branches 8 to 20 mm in diameter, cut them into 15 cm long cuttings, cut the upper cut flat, 1 to 2 cm from the bud, and cut the lower cut into a 45-degree slant, 5 mm from the bud. Divide them into upper and lower ends and bundle 50 per bundle. Soak the lower ends in a 50 mg/kg rooting powder solution for 3 to 4 hours, then remove and set aside.

3. Cutting method: Land preparation requirements are the same as above. Insert the branches into the soil at a 45-degree angle at a plant-row spacing of 20 cm × 40 cm, and cover with plastic film along the bed.

Seed Propagation of Sophora japonica

1. Seedbed selection: The seedling bed for Sophora japonica should preferably be selected as loam or sandy loam with flat terrain, good irrigation and drainage conditions, fertile soil, and deep soil layers. It can adapt to neutral, calcareous, and slightly acidic soils, and can grow normally in mildly saline-alkaline soil (salt content around 0.15%), but grows poorly in dry, poor, thin, and low-lying waterlogged nursery land.

2. Seed treatment

① Soaking method: First soak the seeds in 80°C water, stirring continuously until the water temperature drops below 45°C, then leave for 24 hours and take out the swollen seeds. For seeds that have not swollen, repeat the above method 2 to 3 times until they reach the swollen degree. Cover the swollen seeds with a wet cloth or straw curtain to sweat the seeds and promote germination. After 1.5 to 2 days, when about 20% of the seeds have sprouted, they can be sown.

② Sand storage method: Generally, carry out sand storage of the seeds 10 to 15 days before sowing. Before sand storage, soak the seeds in water for 24 hours so that the sand moisture content reaches 60%, that is, it forms a ball when held in the hand and breaks apart when touched. Mix the seeds and sand evenly at a volume ratio of 1:3, place them in a pit dug in advance, and then cover with plastic sheeting. During sand storage, turn them once every day and keep them moist. When 50% of the seeds have germinated, they can be sown.

3. Sowing method: Spring sowing is generally used, and in Zhuozhou it is suitable to sow in early to mid-April. The sowing rate is 10 to 12 kg per mu. Two methods can be used: ridge sowing or bed sowing. For ridge sowing, the ridge spacing is 70 to 80 cm, the ridge bottom width is 40 to 50 cm, the surface width is about 30 cm, the ridge height is 15 to 20 cm, the sowing width is 10 cm, and the soil cover is 1.5 to 2 cm. Bed sowing can also be used, without ridges, with a row spacing of 60 to 70 cm and a sowing width of 5 cm. After sowing, press the soil so that the seeds and soil are closely combined, and if conditions permit, cover with film.

Planting Management of Sophora japonica

1. Timely final thinning: After sowing, seedlings generally begin to emerge in 7 to 10 days and are fully emerged in 10 to 15 days. For film-covered plots, remove the plastic film when the seedlings have grown 2 to 3 true leaves. When the seedlings are 15 cm tall, thin them in 2 to 3 rounds, with a final plant spacing of 10 to 15 cm, leaving about 8000 seedlings per mu.

2. Transplant management: For landscaping seedlings, they generally can only leave the nursery after 3 to 4 years. Because the buds on the top branches of the seedlings are dense and the internodes are short, the trunk is very easy to bend. In the spring of the next year, transplant the one-year-old seedlings at a plant spacing of 40 to 50 cm and a row spacing of 70 to 80 cm. After planting, the main trunk can be cut back at 3 to 5 cm above the ground. Because the Chinese scholar tree has sprouting ability, a large number of sprouts easily emerge after cutting back. When the tender sprouting branches grow to about 20 cm, select and keep 1 strong upright branch as the main trunk and remove all the other branches. After that, always pay attention to removing tillers and side branches. Temporarily keep the weak side branches on the upper, middle, and lower parts of the main trunk, which is beneficial for preventing the trunk from bending. In this way, the seedling height can reach more than 3 m the next year.

3. Fertilizer and water management: Watering Sophora japonica seedlings should be based on factors such as climatic conditions and soil texture to determine the number of waterings. Under normal circumstances, water 2 to 3 times from after emergence to before the rainy season, and water once before the nursery land freezes. Drain promptly in case of waterlogging. Before sowing, apply about 3000 kg of base fertilizer per mu to the seedling land (mainly organic fertilizer or barnyard manure). In early June, combined with watering, topdress with 8 to 10 kg of quick-acting nitrogen fertilizer per mu. In July to August, topdress with urea, preferably mixed with an appropriate amount of compound mixed fertilizer 12 to 3 times, with each application of about 30 kg. After September, no more watering or fertilizing should be done, so as to promote lignification of the seedlings.

4. Shaping and pruning: As needed, plants can be shaped and pruned into 3 tree forms: natural open-center form, cup form, and natural sympodial trunk form. For the natural open-center form, set the trunk when the main trunk grows to more than 3 m, select and keep 3 to 4 robust branches with appropriate angles as main branches, remove side branches and sprouts below the main branches in time, and during winter pruning, moderately shorten the main branches, leaving 50 to 60 cm, to promote secondary shoots and form a small crown. For the cup form, after setting the trunk, keep 3 main branches as in the natural open-center form. During winter pruning, select and keep 2 side branches on each main branch and shorten them to form 6 small branches. In summer, pinch the tips to control growth. In the winter pruning of the next year, select 2 branches on each small branch and shorten them to form the cup-shaped structure of “3 stocks, 6 forks, 12 branches.” The natural sympodial trunk form means that after keeping the main branches well, later pruning only needs to retain strong terminal buds and upright buds, and develop robust branches at all levels, so that the crown continuously expands.

5. Pest and disease control: The main diseases of Sophora japonica include powdery mildew, canker, and rot disease. They can be controlled by spraying 70% thiophanate-methyl wettable powder at 800 to 1000 times dilution or 50% Tuzet wettable powder at 600 to 800 times dilution. The main pests include the Chinese scholar tree aphid, the Chinese scholar tree looper, armyworm, American white moth, etc., which can be controlled with a compound preparation of 10% imidacloprid wettable powder at 2000 times dilution and 4.5% beta-cypermethrin emulsifiable concentrate at 1500 times dilution, or 2.0% abamectin emulsifiable concentrate at 3000 to 4000 times dilution. Weeding in Sophora japonica nursery land is mainly carried out in the current-year seedling land, and can be done by manual removal or chemical herbicide control. When using chemical herbicides for control, be sure not to spray the agent onto the tree trunks.