Detailed Explanation of Key Technical Points for Hardwood Cutting Propagation of Black Locust
1. Collection and Storage of Cutting Wood
At the end of November, collect current-year superior clone cutting wood from the cutting orchard, or collect current-year seedling stems used for trunk-cutting afforestation, cut into short cuttings 18-20cm long, with each cutting retaining at least 2 buds. The upper cut is 1.0-1.5cm from the upper bud, and the lower cut is made into a single horseshoe shape. After cutting, tie the cuttings in bundles of 50, place them in a cool outdoor spot, and bury them with clean fine river sand (60% moisture content). One layer of cuttings, one layer of sand, trying to ensure every piece of cutting wood contacts sand. Cover each layer of cuttings with sand 3-5cm thick, then place another layer of cuttings. Repeat the procedure of the first layer. The amount of cuttings stored in each place depends on the size of the site, but the storage height generally does not exceed 4 layers. The top layer is covered with river sand to a thickness of no less than 10cm.
2. Cutting Propagation
In mid-to-late April of the following year, after the soil thaws, begin cutting propagation. Before cutting, level and harrow the nursery site finely, and apply 3-5 cubic meters of organic fertilizer per 667 sq m. The cutting density is 20cm x 40cm, with 8300 cuttings inserted per 667 sq m. Use bed cultivation, with a bed surface width of 1.2m, and insert 3 rows per bed. The insertion depth is such that the upper cut is level with the ground (oblique or straight insertion both work). After inserting, firm the soil with your feet, then water thoroughly. After watering, it is best for the upper end of the cutting to be exposed 1-2cm above the ground. 5-7d after cutting, loosen the soil in the seedbed to help raise the ground temperature, maintain moisture, and promote rooting of the cuttings. Units or individuals with the means can use plastic film mulching, and the propagation effect will be better.
3. Bud Removal to Promote Rooting of Cuttings
Black locust cuttings begin to sprout 15-20d after cutting, with a sprouting rate of 100%. Based on the biological characteristic of black locust having a large number of regenerated latent buds, in order to reduce nutrient consumption of the cuttings and promote underground rooting, promptly remove the aboveground buds of the cuttings before rooting; generally this must be done 2 times. The first bud removal is when the buds grow to 3-5cm, cutting off all buds from the base. When removing buds, do not loosen the cuttings, and water once after removal. After the first bud removal, as the temperature gradually rises, after 7-10d the latent buds on the black locust cuttings continue to sprout and grow, reaching a height of 3-5cm; at this time the second bud removal should be carried out. The specific method is the same as the first bud removal. After the second bud removal, the latent buds on the cuttings continue to sprout and grow; at this time attention should be paid to protecting them, and no further bud removal is carried out. After two bud removals, a large amount of callus tissue forms at the lower cut of the cuttings. As the temperature rises and the aboveground part grows, the cuttings begin to root.
4. Management
For hardwood cutting of black locust, in addition to carrying out 2 complete bud removals, other management measures are basically the same as for general tree species. It mainly includes the following: timely watering, fertilizing, loosening soil, weeding, and pest and disease control. Because each bud eye of black locust has many regenerated latent buds, although 2 complete bud removals have been carried out, each cutting can still grow 2-3 young buds at the upper end. Therefore, thinning and bud removal must be carried out. When the seedlings grow to 15-20cm, select one bud with good vigor and robust growth per plant to retain, and remove all the other buds. After thinning, apply a topdressing once, applying 50kg of ammonium bicarbonate per 667 sq m, and water once.