How to grow horse chestnut seeds? Master the key points of sowing immediately after harvest and four-season management

Horse chestnut, also known as Suoluo tree, Tianshi chestnut and monkey chestnut, is a deciduous tree of the Hippocastanaceae family. In the wild it is found only in mountain areas below 700 m altitude in the Qinling Mountains, and it is widely cultivated in the Yellow River basin and in the eastern provinces. It is an excellent street tree and garden tree. It likes light and tolerates slight shade, and is also cold-hardy. It prefers deep, fertile, moist, well-drained soil, has a deep root system and strong sprouting ability, grows rather slowly but lives long, and its leaves are prone to sunscald in hot summers. After the seeds are boiled in alkaline water they taste like chestnuts; they can be eaten, used as medicine, and also pressed for oil to make soap and processed for starch, while the fine, dense wood can be made into utensils.

Seeds do not store well, so sowing immediately after harvest is safest

Horse chestnut seeds lose viability very easily after drying, so once ripe they should be collected promptly and sown immediately. Its capsule is spherical, with a flat, slightly concave top, and can be harvested in late September when it turns yellowish brown; after harvesting, germination ability disappears rather quickly, and although seeds not sown can be stored in sand, the germination rate is not high. In mid-autumn, when the outer skin of the fruit turns from green to brownish yellow and a few have split, collect them and dry them in the shade; after they split naturally, peel off the outer skin and select large, plump, glossy seeds free of pests and diseases. Mix them with moist sand at a ratio of 1:3, store them by the moist stratification method in a well-drained soil pit, and leave ventilation holes.

Sowing methods and four-season management at the seedling stage

Choose nursery land with deep, fertile soil that is convenient for drainage and irrigation, neutral or slightly acidic sandy loam. Two to three months in advance, plow deeply and let the soil dry, apply 2500 kg of decomposed cow or horse manure per mu as base fertilizer, and disinfect with pentachloronitrobenzene. Spring sowing is mostly done by drilling in rows in late March, with a plant and row spacing of 20 x 25 cm and a depth of 3-4 cm, with the hilum facing down, covering with 4 cm of soil level with the bed surface, pressing down lightly, at 150 kg of seed per mu; for sowing in dug holes, the holes are 8-10 cm deep with a plant and row spacing of 30 x 40 cm, covering with no more than 3 cm of soil, then covering with grass to retain moisture and watering thoroughly after sowing. For street trees, the plant spacing is 4-5 m, base fertilizer is added in the holes, and it is best to plant large seedlings with their original soil. For autumn sowing, after collecting seeds in September-October, open furrows and drill, with a row spacing of 20-30 cm and a plant spacing of about 10 cm, hilum facing down, covering with soil and grass, and they sprout and emerge the following spring.

They emerge about one month after sowing. Whether sown in autumn or spring, the bed surface must be kept moist during emergence, and the covering grass should be removed promptly after the seedlings emerge. To prevent sunscald damage to the seedlings, shade frames must be built and water sprayed frequently. In May-June the seedlings like moisture, so continue shading and spraying water, loosen the soil and pull weeds, and apply appropriate topdressing; during the rainy season pay attention to drainage to prevent waterlogging. After the seedlings reach 25 cm in height, loosen the soil and weed, and thin the seedlings on overcast and rainy days. From emergence to early June is the rapid growth period, and the amount of watering should be increased. In July-August the seedlings grow more slowly, so besides loosening the soil and weeding, apply topdressing 2-3 times, pay attention to watering to retain moisture in dry seasons, and promptly prevent and control pests and diseases. This period is also the lignification period, so watering should be reduced to promote thickening of the stem at ground level; for young trees, tending mainly consists of loosening the soil, weeding, earthing up and watering.

Key points of transplanting and routine care

Horse chestnut has a deep main root and few lateral roots, and does not tolerate transplanting. Transplanting must be done with a soil ball, whose diameter should be 6-8 times the tree's diameter at breast height, and it is best done in early spring before buds break or in late autumn after the leaves have all fallen. The planting hole should be dug as large as possible to favor the plant's growth. Planting must not be too deep, to avoid smothering the buds; a depth slightly 3-5 cm above the upper surface of the soil ball is sufficient, and the backfilled soil should be firmed layer by layer.

As for watering, water immediately after planting for the first watering, water again after one week for the second watering, and after another 10 days for the third watering; thereafter water thoroughly once a month. In July-August, when rain is plentiful, water less or not at all; in September-October water thoroughly once each month; in late November or early December water generously for the freeze-up watering; in early March of the following year water for the thaw watering; and in April-May, when spring drought and strong winds cause high transpiration, water once every 15 days.

Horse chestnut likes fertilizer. For base fertilizer, farmyard manure such as cow or horse manure and leaf mold is suitable, as its fertility is mild and it also loosens the soil; it must be mixed evenly with the planting soil. Topdressing is needed throughout the growing season, and large street trees are no exception. In the first year, in June, urea fertilizer can be applied to promote the growth of branches and leaves; in late August, phosphorus and potassium fertilizer can be applied to enhance cold resistance; and in autumn apply leaf mold once more. Pruning is carried out each year in winter after leaf fall or in the following spring before buds break. The crown is a natural round-headed shape, and it is best to maintain the original crown form: thin out overly dense branches, shorten overly long branches, and cut out dead branches, diseased and pest-infested branches, inner-canopy branches and slender branches, so that the branches are evenly distributed, well ventilated and lit, and nutrients are concentrated for supply.