Cultivation techniques of crape myrtle stem seedlings

Cultivation techniques of crape myrtle stem seedlings

The genus crape myrtle, alias crape myrtle, full red, itchy tree, shrub or small tree, has smooth bark, four-angled young branches, alternate or opposite leaves, purple or pink flowers, and a long flowering period. it is a famous ornamental tree and street tree in town courtyard from early July to mid-October. Crape myrtle seedlings have strong germination rate and well-developed lateral branches, which is easy to form bushy or curved trunk when cultivating crape myrtle seedlings, which can not meet the requirements of greening tree species. therefore, combined with the production practice of breeding crape myrtle seedlings for many years, a set of techniques for cultivating crape myrtle seedlings are summarized, and the main cultivation techniques are summarized as follows.

1 nursery site selection

The plots with convenient transportation, deep soil layer, fertile soil, good drainage and irrigation, sufficient light and soil pH value of 6.5-7.2 were selected as nurseries.

2 soil preparation and digging holes before seedling planting

Crape myrtle grows slowly when rotary tillage is used in the whole garden before freezing, and the cultivation of single stem seedlings is mainly to cultivate tree trunks. In order to cultivate seedlings with breast diameter of 5~7cm, the hole should be dug according to the row spacing of 1m × 1m, and the hole size is 50cm × 50cm × 50cm, and the topsoil and subsoil should be stacked separately. After thawing in spring, first backfill the skin, then backfill the subsoil. When the soil is backfilled to the off-ground level about 25cm, each hole is mixed with fully mature farm fertilizer 10kg + phosphate fertilizer 0.5kg, and in the backfilling hole, the backfill soil should be higher than the 15~20cm of the ground surface.

(3) transplanting seedlings

The transplanting time was from late February to the first and middle of March, and 1-2-year-old cuttings or seedlings were selected. The planting depth is that the soil of the original nursery is flush with the ground, compacted with backfill and irrigated with root water. 667 plants were planted in 667m ~ 2.

3.1 watering and topdressing after transplanting

Often observe the soil moisture, usually watering 2 or 3 times before the rainy season in March to June. Dig 20cm deep holes on both sides of the trunk in the crown projection in the middle of April before each watering, apply urea 0.1-0.2 kg per tree from late May to early June, and apply urea 0.1~0.2kg to each plant. The period from late July to mid-August is the rapid growth period of crape myrtle, and it is also the flowering and fruiting stage. combined with the application of nitrogen, phosphorus and potassium compound fertilizer 0.2~0.3kg per plant can promote the growth of crape myrtle, supplement a large amount of nutrients consumed by flowering and fruiting, and the amount of fertilizer increases with the increase of tree age.

3.2 ploughing, weeding and deep turning

Weeding must be done once after rain and watering, and weeding and loosening should be carried out at the same time, especially on a sunny day in July. Deep 10~15cm. From September to October, the whole garden was turned deep once every other year. The depth of the tree disk is 5~10cm, and the tree disk is turned out to be 20~30cm.

3.3 timely pruning to ensure normal growth of the trunk

Crape myrtle has strong sprouting ability, developed lateral branches and weak top advantage, which is most likely to form shrubs or curved trunk in the process of cultivation, which can not meet the application specifications of garden greening and street trees. therefore, reasonable pruning must be carried out. After years of practical experience, it is proved that the pruning period should be in the growing period, that is, from late June to mid-July. In the same year, crape myrtle cuttage seedlings blossomed. June to August is the fast-growing period of crape myrtle, and it is also the flowering and fruit stage of crape myrtle. When pruning in July, the inflorescences and fruits are also cut off, which can save the work of cutting off inflorescences and fruits, concentrate the nutrition of seedlings, promote trunk thickening and height growth, and then form straight trunks and good crown shapes.

Generally, pruning starts from the second year of planting. For tufted crape myrtle seedlings, the sturdy and upright branches should be selected as the trunk, and the rest will be cut off. After cutting off useless lateral branches, buds will grow again under the cut mouth. When the buds grow to 5cm or so, they should be removed in time. Sprouts should be smeared 2 or 3 times a year at any time. For those crape myrtle seedlings with poor trunk growth or bending, cut off the stem at 5~10cm above the ground. After cutting, new branches germinate again from the base of the cutting mouth, and a vigorous new shoot is selected to be cultivated as the trunk, and all the other new shoots are erased. When cutting off the germinating lateral branches at the base of the trunk, the seedlings should pay attention to the cutting mouth to be close to the trunk, the cut should be smooth, and the sprouts buried in the soil. Be sure to remove the soil at the base of the trunk, and then cut off the germinated branches so as not to sprout new branches again, for the side branches from the trunk. According to the growth potential of crape myrtle seedlings, the side branches on the trunk of the tree height should be cut off year by year, or part of the side branches on the trunk with a height of 1 cm 3 should be cut off year by year, and the net height of the trunk (the height from the ground to the first branch point of the crown) should be kept about 1 cm 3 of the height of the tree. Sparsely cut off some of the lateral branches below the dry height, cut short the vigorous branches (usually light pruning, cut off the length of the branches 1 to 4 and 1 to 2), and cut off the branchlets near the top of the trunk to facilitate the cultivation of the trunk and cut off a small amount of inflorescences and fruits. In the management of the growing season, always check the buds on the net dry height and erase them as you see them. The net dry height is increased year by year, and the net dry height is always about 1x3 of the tree height. when the net dry height reaches the specification of green tree species, it is more than 1.5m, stop pruning the net dry height and focus on crown cultivation.

3.4 Disease and pest control

The main diseases and insect pests of crape myrtle include powdery mildew, brown spot, yellow diamondback moth, crape myrtle aphid aphid, crape myrtle scale. After falling leaves in winter, it can eliminate the centralized burning of dead branches and leaves and eliminate the source of overwintering diseases and insect pests. Spraying 5 °Be stone sulfur mixture or 50% carbendazim wettable powder before germination can control the occurrence of powdery mildew and brown spot. 2.5% kung fu EC 2500 times + 1.8% avermectin 2500 times solution is used in the growing season. Or alternately spraying 2000 times of the liquid can fully control the occurrence of yellow diamondback moth, crape myrtle aphid and crape myrtle scale.

3.5 seedlings coming out of the nursery

It is common to cultivate qualified seedlings with breast diameter of 5~6cm, plant height of more than 2.5m, crown width of 1.6 to 2.5m, net dry height of more than 1.5m, straight trunk, reasonable branches and symmetrical crown in 5-6 years. Can be out of the nursery according to the market demand.