Detailed Explanation of Key Points for Raising Northern Chinese Parasol Tree Seedlings

The Chinese parasol tree, also known as green paulownia (Firmiana simplex), is a deciduous tree of the genus Firmiana in the Sterculiaceae family. Its crown is oval, the trunk is straight and upright, the bark is fresh green and smooth, and its emerald leaves cast dense shade. It has strong adaptability and grows rapidly, and is mostly planted as a street tree and in courtyards. At present it is recognized by more and more people, and has high promotion value and good market prospects. The seed sowing and seedling raising techniques for the Chinese parasol tree are introduced as follows.

1 Seed collection and preparation

Collect seeds from 15-30 year old mother trees that grow robustly, have straight trunks and no pests or diseases. The seeds of the Chinese parasol tree mature from late September to early October; the fruit skin is yellow and wrinkled, and the seeds have already split open before they are fully mature, so the seeds scatter easily, and the fruits should be collected promptly together with the fruit stalks. After collecting the seeds, spread them out to dry in the sun, turning them 2-3 times a day, rub off the fruit skin, and after removing impurities they can be stored dry or in sand. Because the seed coat of the Chinese parasol tree is thin and the seeds easily lose water and dry out, losing their germination capacity, sand storage is preferable. The 1000-seed weight is about 125 g, and the germination rate is 85%-90%.

2 Selection and treatment of the nursery site

2.1 Selection of the nursery site

Choose soil that is deep, loose, rich in humus and well drained. It can grow on acidic, neutral and calcareous soils, but should not be planted in waterlogged lowlands or saline-alkali land. After waterlogging, the roots rot easily, and being flooded for 5 d can kill it.

2.2 Disinfection of the nursery site and spraying of herbicide

To prevent damage from diseases and insects during the seedling stage, soil disinfection can be carried out. Apply 1-2 kg of 70% dexon powder per 667 sq m, mix it with fine soil at a ratio of 50 times, stir evenly and broadcast it uniformly to prevent seedling diseases; at the same time, broadcast 1.5-2.5 kg of 3% carbofuran granules or spray 0.125%-0.2% phoxim solution and mix it into the soil to control underground pests. The Chinese parasol tree is not tolerant of weed infestation, so chemical weeding can be carried out on the nursery site 20 d before sowing. Use 50% acetochlor at 50 mL per 667 sq m, diluted in 50 kg of water, and spray evenly; the effective period is about 2 months.

2.3 Land preparation and bed making

In early winter, deep plow the nursery site to 30 cm, break up the clods so that they become granular, and apply 1000 kg of decomposed organic fertilizer per 667 sq m. The bed surface is 100 cm wide and 20 cm high, the path is 40 cm wide, and the length depends on the site; dig drainage ditches all around so that no water accumulates in the ditches after the rain stops.

3 Seed disinfection and germination acceleration

First, 30-40 d before sowing, carefully select the seeds, choosing well-developed, plump, large seeds free of pests and diseases, then disinfect the seeds. They can be soaked for 2 h in a 0.5% potassium permanganate solution (or soaked for 30 min in a 3% potassium permanganate solution), taken out and sealed for 30 min, then rinsed several times with clean water. Finally, soak the seeds in warm water to accelerate germination, using warm water at 60°C-80°C (with the water surface covering the seeds by more than 10 cm); after 24 h, take them out and mix them with wet sand in a pile 20-30 cm thick, cover with wet burlap sacks or wet rice straw, and place in a wind-sheltered, sunny spot to accelerate germination, sprinkling water 2-3 times a day; when more than 30% of the seeds have split open, they can be sown.

4 Sowing and mulching with straw

Carry this out in spring after the soil thaws, from late March to early April. Drill sowing with a row spacing of 25 cm, sowing rate about 15 kg/667 sq m; sowing must be uniform, and soil should be covered as sowing proceeds. The soil covering thickness is 1.0-1.5 cm, and the thickness must be uniform to facilitate uniform emergence. After sowing, cover with a layer of rice straw (just enough that the ground is not visible), keep the soil moist, and seedlings emerge in about three weeks.

5 Removing the straw and thinning seedlings

When the seeds have sprouted and about 30% of the cotyledons have emerged, the mulch straw can be removed. When the seedlings reach about 5 cm in height, carry out the first thinning; when the seedlings reach about 10 cm in height, carry out the second thinning, with a plant spacing of 20-30 cm, and at the same time pull out weeds.

6 Fertilizer and water management

Management measures differ at different stages, and irrigation and fertilization should be adapted to local conditions.

6.1 Irrigation

From after sowing to the early stage of seedling growth, water frequently in small amounts to keep the soil moist, so as to facilitate seed germination and emergence and the growth of the seedling root system; in early July the seedlings enter the rapid growth stage, so increase the amount of irrigation, applying more water less often, to maintain the water balance of the seedlings; in mid- and late September, height growth stops, so stop irrigation to prevent the seedlings from being insufficiently lignified and thus affecting safe overwintering.

6.2 Fertilization

After the true leaves of the seedlings appear, ammonium sulfate or ammonium bicarbonate can be applied as a top dressing, at 30-35 kg/667 sq m, applied in 3 split applications; phosphate fertilizer is applied at 2.5-2.8 kg/667 sq m, at a concentration of about 0.7%-1.5%; potassium fertilizer is applied at 2 kg/667 sq m, at a concentration of about 0.5%. Generally spray 2-3 times. After September, to prevent excessive vegetative growth of the seedlings and promote lignification, nitrogen fertilizer should be stopped and phosphorus and potassium fertilizers increased, so that the seedlings become firm, which is beneficial for overwintering.

7 Cultivation of large seedlings

In the first two years after planting, loosen the soil and weed frequently, strengthen fertilizer and water management, and take care to protect the young trees; never damage or prune the branch tips, so as to avoid dead tips and damage to the tree shape.

8 Pest and disease control

8.1 Chinese parasol tree psyllid

Its nymphs and adults gather on the underside of leaves or on tender young branches and trunks to suck sap. The white flocculent waxy substance secreted by the nymphs can block the stomata, causing the leaf surface to appear pale and shrunken; at the same time it easily invites mold parasitism, and in severe cases the leaves fall early, the branch tips dry up, and the bark becomes rough and brittle and easily broken by wind. When the pest occurs, spray with 25% trichlorfon or malathion at 800 times dilution, or 40% dimethoate at 2000 times dilution, or 80% dichlorvos emulsifiable concentrate at 1000-1500 times dilution.

8.2 Slug moth

The larvae feed on the lower epidermis and mesophyll of the leaves, and in severe cases eat the leaves completely, leaving only the veins and petioles, seriously affecting plant growth. In winter, pick off the cocoons or crush the cocoons on the trunks to reduce the source of the pests. During the period when the pest occurs, promptly spray evenly with 40% phoxim emulsifiable concentrate at 1000 times dilution, 45% beta-cypermethrin at 1500 times dilution, or 20% Luan at 1000-1500 times dilution.

9 Overwintering and cold protection

In winter, wrap young trees with straw for cold protection; if conditions permit, apply fertilizer and irrigate once each year before the onset of winter and in early spring.