What are the key cultivation techniques for Spiraea pubescens?

Spiraea pubescens, also known as soft-haired spiraea, belongs to the genus Spiraea in the Rosaceae family. It was introduced from Tieling, Liaoning, in March 2001 by the Beilin Nursery Stock Breeding Demonstration and Extension Center of Changji Prefecture. Its local growth performance is as follows: deciduous shrub, plant height about 80 cm, clump-forming, pink flowers, terminal panicles. Flowering period in June, slender branches, good ornamental value of flowers. It has now been extended to Karamay, Shihezi and other places.

I. Biological Characteristics

Spiraea pubescens is a deciduous shrub, up to 2 m tall. Young branchlets are brownish-yellow, covered with short hairs; when old, grayish-brown, hairless; buds are ovate or nearly spherical, covered with scales on the outside. Leaves are rhombic-ovate to elliptic, 2-4.5 cm long, 1.5-2.5 cm wide, with deeply serrate margins above the middle, sometimes 3-lobed, sparsely pubescent above, grayish short-pubescent below; petiole 2-4 mm long, short-pubescent. Umbel has a peduncle and many flowers; pedicel 0.7-1.2 cm long; bracts linear, short-pubescent; flower diameter 5-7 mm, calyx tube campanulate, hairless outside, grayish-white short-pubescent inside, calyx lobes triangular, petals ovate, broadly ovate or nearly circular, 2-3 mm both in length and width, stamens numerous, nearly as long as petals, disc composed of 10 lobes forming a ring, style shorter than stamens. Fruit dehiscent, persistent style terminal, with erect persistent sepals. Flowering period May-June; fruiting period July-August.

II. Propagation Methods

1. Cutting Propagation

Either hardwood cuttings or greenwood cuttings can be used. For hardwood cuttings, before early spring bud break, select robust branches with plump buds that have been stored in sand, cut them into 12-16 cm cuttings, and insert them into the cutting bed as they are cut. It is best to cover with plastic film to retain heat and moisture; the rooting rate can reach over 95%. Greenwood cuttings are generally carried out in June-July, or earlier if a greenhouse and ready branches are available. The method is to select semi-lignified branches, cut them into 5-8 cm cuttings, keep 2-3 small leaves, and insert them into a full-light mist propagation tray or greenhouse shed. They should not be inserted too deep, and roots will form after about 2 weeks.

2. Sucker Propagation

It is suitable to carry out before spring bud break. Dig out the root sucker seedlings around the spiraea for afforestation and landscaping.

3. Seed Propagation

Collect seeds in autumn after the seeds mature, store them dry, and drill-sow in spring. Sowing rate 2.5-3.5 kg per 667 sq m, row spacing 40-50 cm. The seedling bed depends on the terrain; flat ground is suitable for convenient irrigation with water. The length and width of the seedbed are preferably 2 x 6-8 m. Sowing in a north-south direction is preferable. Cover with 2-3 cm of soil; if conditions permit, it is best to cover with a mixture of river sand and sawdust. Generally, roots form and seedlings emerge in 5-30 days. During the seedling stage, loosen the soil, weed, and thin seedlings in time. When seedlings are 3-4 cm tall, apply quick-acting fertilizers such as urea.

III. Field Management

Spiraea pubescens likes light, tolerates cold, likes water and fertilizer, has low requirements for soil, grows fast, has strong branching ability, and is relatively simple to manage. Generally, irrigate 8-10 times a year, pay attention to loosening soil and weeding in time, prune dead branches and leggy branches in summer, and prune dried fruiting branches in September. This can strengthen the tree vigor, maintain the crown shape, and make flowering and fruiting better the following year.

Spiraea pubescens flowers from May to June, with pink flowers densely arranged on all sides and good ornamental value. It can be used as courtyard and landscape greening material; it is suitable for clump planting, used for various patterns and shapes; it can also be used as a hedge. Before winter, irrigate once with winter water, and pay attention to preventing rodent damage.