Detailed Explanation of Softwood Cutting Propagation Techniques for Cherry Blossom
Cherry blossom (Prunus serrulata Lindl) is a deciduous tree of the Rosaceae family, with a plant height of 5-25 cm. Its inflorescences are corymbose or racemose, composed of 3-5 flowers. Flower colors include white and pink, single or double petals. Flowers and leaves may appear together or flowers may bloom before leaves. The flowering period is April-May. When spring arrives and flowers bloom, the tree is covered in blossoms competing in beauty, with brightly colored, fragrant flowers that are elegantly understated. It is a famous flowering tree for landscaping.
Cherry blossoms are usually propagated mainly by grafting, mostly using single-petaled cherry blossoms or cherry trees as rootstock, with cut grafting or cleft grafting carried out before flowering in early spring. There are very few reports on the application of cutting propagation. In recent years, our experiments on softwood cutting propagation of cherry blossoms showed that within 25 d after cutting, the average rooting rate was above 95%, with a maximum of 20 roots per plant, and most were cortex-type roots, with some callus-type roots. The transplanting survival rate was above 90%. The techniques are described below.
1 Cutting collection and treatment
From early to mid-June to early to mid-September, collect semi-lignified branches that have sprouted in the current year, cut them into 10-15 cm long segments, keep 2-3 leaves at the top of each segment, and remove the remaining leaves together with their petioles. The lower cut of the cutting should be made with a sharp blade in a flat cut, requiring a smooth cut surface. Bundle the prepared cuttings into small bundles of 50 or 100 pieces. In a cool, moist place, soak the basal 3-4 cm of the cuttings in a solution of ABT Rooting Powder No. 1 (developed by the ABT Research Center of the Chinese Academy of Forestry) at a concentration of 50 mg/L for 5-8 h, or in a solution at a concentration of 100 mg/L for 2-4 h.
2 Cutting method and post-cutting management
2.1 Cutting bed setup
Choose a cool, well-drained location to build a small plastic arch shed 1.2-1.5 m wide and 5.0-6.0 m long, with an arch height of 70-90 cm. First dig down 25 cm at the bottom, then lay about 10 cm thick cinder, and on top lay about 10 cm thick expanded perlite or river sand as the cutting substrate, and water thoroughly.
2.2 Cutting
Insert the cuttings into the cutting bed at a plant spacing of 3 cm and a row spacing of 5 cm (it is best that the leaves of the cuttings do not overlap each other). When cutting, first make holes with a short wooden peg slightly thicker than the cutting, then place the cutting into the hole, firm the substrate around the cutting so that the substrate is in close contact with the cutting. The cutting depth is 4-5 cm.
2.3 Post-cutting management
Immediately after cutting, sprinkle thoroughly with clean water, cover the shed film tightly, and maintain relative humidity above 95%. Thereafter, spray an appropriate amount of clean water once every morning. The temperature inside the arch shed should preferably be maintained at around 30°C. If it exceeds 35°C, water may be sprinkled to lower the temperature. The substrate temperature should preferably be around 25°C. In the early stage after cutting, the amount of water sprinkled should be somewhat larger, then gradually reduced. When the cuttings begin to root (generally about 15 d after cutting), ventilation may be carried out appropriately in the morning and evening, and then the ventilation amount should be gradually increased and the ventilation time extended. When the roots of the cuttings reach 3-5 cm in length and each cutting has 3-5 roots, they can be transplanted.
3 Transplanting
Before transplanting, gradually open the shed film and harden the seedlings for about 7 d, and reduce the amount of water sprinkled. During transplanting, directly move the hardened cuttings into the field, water thoroughly immediately, and shade with a sunshade net for several days, avoiding exposure to strong sunlight. Alternatively, they may first be moved into nutrient pots (the culture soil should have good permeability), then placed in a small arch shed after transplanting, watered thoroughly, covered with shed film, and kept moist and shaded for several days. At the beginning, ventilate every morning and evening, then gradually increase the ventilation amount after 2-3 d, open the shed film after 10 d, remove the shading material, and after hardening the seedlings for another 4-5 d, they can be moved into the field.