Methods and Precautions for Propagating Flowers by Cuttings
Cutting propagation makes use of the regenerative ability of plant roots, stems, leaves, and buds, so that under suitable conditions they grow roots and sprout to form new plants. Its advantages are: it maintains the characteristics of each plant; the flowering period comes earlier than with seed propagation; the propagation method is simple, the materials are easy to obtain, and the survival rate is high; when conditions permit, it can be done in all four seasons; and species that cannot set seed can be propagated by this method. The disadvantages are: plants grown from cuttings have shallow root systems and a relatively short lifespan. Stem cuttings include hardwood cuttings and softwood cuttings.
1. Hardwood cuttings: This method is mostly used for deciduous flowering trees and shrubs such as pomegranate, rose of Sharon, hibiscus, crape myrtle, winter jasmine, and poinsettia. It is carried out in early spring before the sap begins to flow. Select vigorous, plump 1- to 2-year-old branches, take the middle section, and cut them into 10—15 cm long pieces as cuttings; they need to have 2—3 buds, and the terminal bud of the cutting must be plump and intact. At the upper end, cut flat 0.5-1 cm above a bud; at the lower end, cut slantwise 0.5-1 cm below a bud, with the bud on the side of the tip of the slant cut, and insert it into the cutting medium to a depth of 1/2 of the cutting. For most tree species, hardwood cuttings are stored in sand in the ground over winter before winter arrives, and then inserted in spring. Some tropical and subtropical flowering trees and shrubs can also be propagated earlier in a greenhouse.
2. Softwood cuttings: This method is mostly used for greenhouse flowers such as fuchsia, geranium, and begonias; outdoor herbaceous flowers such as scarlet sage, dahlia, and verbena; and evergreen broad-leaved flowering trees and shrubs such as jasmine, azalea, banana shrub, camellia, and osmanthus. It is carried out from late May to September. Select semi-lignified leafy branches of the current year as cuttings; for example, semi-lignified branches taken from slightly below the tip after flowering are best. The cuttings are about 6-10 cm long and must have 2—3 buds. The cutting method is the same as for hardwood cuttings, and the lower leaves are removed; part of each upper leaf can be cut off as appropriate to reduce evaporation. The survival rate is highest when cuttings are inserted immediately after being cut. When taking cuttings of poinsettia, geranium, oleander, and the like, a large amount of sap often flows from the cut, so be sure to wait until the cut has dried before inserting, otherwise the cut is prone to rot after insertion and difficult to keep alive.
3. Leaf cuttings: Species such as bedding begonia, chrysanthemum, echeveria, and snake plant, which can grow adventitious roots and adventitious buds at the leaf veins or leaf stalk, can be propagated by leaf cuttings to grow into new plants. When cutting off leaves, for those with a leaf stalk, keep about 3 cm of the leaf stalk and cut off part of the thin, tender leaf margin, then insert the leaf stalk into the medium; for those without a leaf stalk, cut at the intersections of the leaf veins with a knife and lay the leaf flat on the medium so that it is in close contact with the medium, or use a bamboo stick to fix the leaf veins in the medium, so that roots can form at the leaf veins and grow into a new plant. Snake plant has fleshy sword-shaped leaves, which can be cut crosswise into leaf sections about 5 cm long as cuttings and inserted upright into sand; when inserting, do not put them upside down, and new roots can form at the base to produce a new plant.
4. Leaf-bud cuttings: For rubber plant, hydrangea, jasmine, hibiscus, and others, although roots can form at the leaf stalk and leaf axil during leaf cuttings, buds cannot sprout, so they cannot grow into new plants. Therefore, a leaf with an axillary bud at its base must be used for cuttings so that it can develop into a new plant.
5. Root cuttings: For flowering plants whose roots can grow adventitious buds, such as chaenomeles, peony, Chinese trumpet creeper, kiwifruit, hypericum, wintersweet, garden phlox, and bleeding heart, roots can be used as cuttings for propagation. When repotting flowering trees and shrubs, cut 5—10 cm root sections and insert them upright or slantwise into the soil, without reversing the top and bottom; the upper end should be level with the soil surface, and after new shoots grow, earth up around them as appropriate.
No matter which cutting method is used, after insertion be sure to water thoroughly, then cover the cutting pot with glass or plastic film to maintain a certain temperature and relatively high humidity, place it in semi-shade, strengthen management, and after rooting, transplant and grow it on. To achieve a high survival rate for cuttings, in addition to selecting good cuttings, the medium is also very important; the medium must both drain well and have a certain water-holding capacity. Vermiculite, perlite, furnace slag, and rice-hull ash are relatively good cutting media. The medium must be maintained at an air temperature above 20°C, that is, the atmospheric temperature must be above 25°C, so that the cut end of the cutting can heal and root easily.