How to Grow Lilacs? A Complete Guide to the Latest Cultivation Methods
Lilac is the collective name for deciduous shrubs or small trees of the genus Syringa in the family Oleaceae. The flowers of quite a few species are raw materials for extracting essential oils and blending fine perfumes, and the plants have lush branches and leaves with elegant, fragrant flowers, so they are widely cultivated in gardens for ornamental purposes and are treasures of the garden. Let us take a look below at how to grow lilacs!
Growth Habits of Lilac
Lilac loves light and prefers warmth, humidity and plenty of sunshine. It tolerates slight shade, but grows weakly in shady or semi-shady spots and blooms sparsely. It has a certain cold hardiness and fairly strong drought tolerance. It is not demanding about soil and tolerates poor soil, but prefers fertile, well-drained soil. It should not be planted in low-lying ground, as waterlogging can cause disease and even kill the whole plant. Bare-root transplanting is done after leaf fall and before bud break, choosing a sunny spot with fertile, well-drained soil. It is mainly distributed in subtropical subalpine zones, on forest edges and under forests from the warm temperate to temperate zones, and in sunny thickets of the cold temperate zone.
Propagation Methods of Lilac
1. Grafting: Grafting is the main propagation method, and either bud grafting or scion grafting can be used. The rootstock is usually European lilac (Syringa vulgaris) or Chinese privet (Ligustrum sinense). In North China, bud grafting is generally carried out from late June to mid-July. The scion is a plump dormant bud on a vigorous current-year branch, grafted by the shield bud method without wood, onto the rootstock trunk 5-10 cm above the ground.
2. Sowing: Seeds can be sown in pots indoors or in open-field beds in spring and autumn. In the north, spring sowing is preferable, carried out in a cold frame in pots in late March, with the temperature kept at 10-22°C; seedlings emerge in 14-25 days, with a germination rate of 40-90%. For open-field spring sowing, it can be done from late March to early April. Before sowing, the seeds need to be stratified in sand at 0-7°C for about 2 months, and seedlings emerge half a month after sowing.
3. Cuttings: One month after flowering, select vigorous semi-lignified current-year branches as cuttings. The cuttings are about 15 cm long and are treated with a 50-100 PPM aqueous solution of indolebutyric acid for 15-18 hours. After insertion, cover with plastic film; roots form after 1 month, with a rooting rate of 80-90%. Lignified branches can also be taken as cuttings in autumn and winter, usually buried in the open field and inserted the following spring.
Cultivation Methods for Lilac
1. Planting: Lilac should be planted in a sunny spot with loose, well-drained soil. It is generally planted bare-root in spring before buds sprout, with a spacing of 3 m between plants. For 2-3 year old seedlings, the planting hole should be 70-80 cm in diameter and 50-60 cm deep. Apply 100 g of fully decomposed organic fertilizer and 100-150 g of bone meal per hole, mixing thoroughly with the soil as a base fertilizer.
2. Watering: After planting, water thoroughly, then water once every 10 days, loosening the soil after each watering to conserve moisture. Irrigation can vary by region. In North China, April to June is the season when lilac grows vigorously and blooms, so water thoroughly 2-3 times a month. After July the rainy season begins, so pay attention to drainage and waterlogging prevention. By mid-November, before winter sets in, water thoroughly.
3. Pruning: When planting large 3-4 year old seedlings of lilac, the above-ground branches should be heavily pruned, generally cutting the trunk back 30 cm above the ground, and the following year it will produce abundant flowers. Pruning is done before bud break in spring, mainly removing thin, weak branches and overly dense branches, while reasonably keeping good renewal branches. After flowering, remove the remaining flower spikes.
4. Fertilizing: Lilac is generally not fertilized, or only lightly fertilized. Never apply too much fertilizer, otherwise it will cause excessive vegetative growth, which affects flower bud formation and instead reduces flowering. However, after flowering, some phosphorus, potassium and nitrogen fertilizer should be applied.
5. Pests and diseases: Lilac diseases include bacterial or fungal diseases such as wilt disease, leaf blight and verticillium wilt, as well as diseases caused by viruses. These diseases generally occur during periods of high temperature and high humidity in summer. Pests include caterpillars, stinging moths, leaf-mining moths, giant hornets and scale insects, and attention should be paid to their control.