Buddleja Planting Methods and Cultivation Techniques
Buddleja is a shrub in the genus Buddleja, family Scrophulariaceae, reaching up to 5 m in height. The branchlets spread outward and bend downward; young branches and leaves are membranous to thinly papery, narrowly ovate, narrowly elliptic to ovate-lanceolate, rarely broadly ovate, with finely serrate margins, dark green above, sparsely covered with stellate short pubescence, becoming glabrous later; flat above, slightly raised beneath; between the petioles there are 2 ovate or semicircular stipules; the inflorescence is a terminal raceme or paniculate cyme; the bracteoles are linear-lanceolate; the calyx is campanulate, with lanceolate, membranous calyx lobes.
Propagation Methods
Large-leaved Buddleja (Buddleja davidii) can be propagated by sowing, cuttings, division, and other methods, with cuttings being most commonly used in production. The seeds are tiny; before sowing, level the ground and water it thoroughly. After sowing, do not cover with soil or cover with only a thin layer of sifted fine soil, keeping the soil moist; the covering soil should be shallow. During the seedling stage, provide appropriate shade to avoid exposure to strong sunlight. Transplant in the second year, and they will bloom in 3 years.
For cutting propagation, root cuttings are easy to propagate, and softwood cuttings can also be used; collecting semi-lignified branches in mid-June for cuttings makes rooting even easier. Select new shoots sprouting from vigorous branches and cut the cuttings at about 10 cm. Keep the top two leaves and cut the remaining leaves in half, soak in water for about 60 minutes, dip the cut end in rooting powder, insert into the cutting bed, and promptly mist with water and provide shade.
For division propagation, from late March to early April in spring, dig up the clustered shoots around the base of the plant, remove the adhering soil, cut them apart with a sharp knife, coat the cut surfaces with plant ash, and replant the divisions; all will survive.
Planting location: Be sure to choose a high, dry, wind-sheltered, sunny site with good drainage for cultivation; do not plant beside fish ponds. When planting in North China, 1-3 year old seedlings require cold protection in winter to ensure safe overwintering.
Water and fertilizer management: When planting, apply 2-3 shovelfuls of compost per plant as a base fertilizer; generally no additional topdressing is needed, though in summer 1 application of fertilizer may be given as appropriate to promote flower bud growth. From spring bud break to flowering, water 3-4 times; in relatively dry summers, water more; before winter, water once with a freezing-water irrigation.
Shaping and pruning: After flowers fade, it is best to cut off the spent flowers along with a section of the branch to encourage new shoots, or before winter cut back or shorten the aboveground parts; in the following spring new shoots will emerge and still flower normally. In spring, weak branches often dry up and should be pruned when buds sprout; overly old branches can be renewed after flowering.