A Detailed Guide to the Latest Methods of Propagating Japanese Pagoda Tree (Sophora japonica) from Seed

The Japanese pagoda tree (Sophora japonica) is also known as the pagoda tree, huairui, douhuai, baihuai, xiyiehuai and so on. It originated in China and is now widely cultivated across the northern and southern provinces and regions. It is highly adaptable and has considerable planting value. There are many propagation methods, but seed propagation is the most commonly used, and propagating the Japanese pagoda tree from seed is not difficult. Let's take a look at the seed propagation methods for the Japanese pagoda tree below!

Choosing a Seedbed Site for the Japanese Pagoda Tree

For raising Japanese pagoda tree seedlings, the nursery site should preferably be level, with good drainage and irrigation conditions, fertile soil and a deep loam or sandy loam layer. It can adapt to neutral, calcareous and slightly acidic soils, and can grow normally in mildly saline-alkaline soil (with a salt content of about 0.15%), but it grows poorly in dry, barren and low-lying waterlogged nursery sites.

Seed Treatment of the Japanese Pagoda Tree

1. Soaking method: First soak the seeds in 80°C water, stirring constantly 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 state. Cover the swollen seeds with a wet cloth or straw curtain to keep them warm and promote sprouting. After 1.5 to 2 days, when about 20% of the seeds have begun to sprout, they can be sown.

2. Sand storage method: Generally, the seeds are stored in sand 10 to 15 days before sowing. Before sand storage, soak the seeds in water for 24 hours, and bring the sand's moisture content to 60%, that is, it forms a ball when squeezed in the hand and crumbles at a touch. Mix the seeds and sand thoroughly 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 the mixture once every day and keep it moist. When 50% of the seeds have germinated, they can be sown.

Sowing Methods for the Japanese Pagoda Tree

1. Sowing time: Spring sowing is generally used, preferably in early to mid-April. The sowing rate is 10 to 12 kg per mu.

2. Sowing method: For ridge sowing, the ridge spacing is 70 to 80 cm, the ridge bottom width is 40 to 50 cm, the top 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. Flat sowing without ridges can also be used, with a row spacing of 60 to 70 cm and a sowing width of 5 cm. After sowing, press the soil down so that the seeds are in close contact with the soil; if conditions permit, cover with plastic film.

Thinning and Transplanting of the Japanese Pagoda Tree

1. Timely thinning: After sowing, Japanese pagoda tree seeds generally begin to emerge in 7 to 10 days and emerge completely in 10 to 15 days. For plots covered with plastic film, remove the film when the seedlings have grown 2 to 3 true leaves. When the seedlings are 15 cm tall, thin them out in 2 to 3 rounds, with a final spacing of 10 to 15 cm between plants, leaving about 8,000 seedlings per mu.

2. Transplanting management: For landscaping seedlings, they generally take 3 to 4 years before they can leave the nursery. Because the buds on the upper branches of the seedlings are dense and the internodes are short, the trunk is very prone to bending. In the spring of the following 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. Since the pagoda tree has sprouting ability, a large number of shoots easily emerge after cutting back the trunk. When the young sprouts grow to about 20 cm, select and keep 1 strong, upright shoot as the main trunk and remove all the other branches. From then on, pay attention at all times to removing tillers and side shoots. Temporarily keep the thin, weak side branches on the upper, middle and lower parts of the main trunk, as this helps prevent the trunk from bending. In this way, the seedling height can reach more than 3 m the following year.