Propagation Methods and Management Tips for Sweet William (Dianthus barbatus)
Propagation methods: sowing and cutting propagation.
1. Sowing propagation can be done in spring or autumn. In autumn, sow in the open field from September to October. The optimum germination temperature is 1-0 to 20°C. Sweet William seedlings need a month and a half of low-temperature vernalization before they can differentiate flower buds, so seeds sown in spring will not bloom that year, producing only leaves, and will not bloom until early summer of the following year. Before frost, seedlings should be 2-3 cm tall.
For field sowing, sow 200 seeds per sq m. If growing seedlings for transplant production, move them elsewhere after they become established, and the rate can be doubled, that is, 400 seeds per sq m; for sowing and raising seedlings in a greenhouse, the rate can be increased to 600 seeds per sq m. If using the plug tray seedling method, a 108-cell tray is suitable.
Field sowing. Garden soil is fine; any soil that is not too heavy will do. For plug tray seedling raising, peat soil, sand and vermiculite can be mixed at a ratio of 1:1:1 to make a composite substrate.
2. Cutting propagation. Cuttings are used to propagate a particular variety. As long as conditions are suitable, cuttings can be taken throughout the growing season, but they will not bloom that year. Autumn and winter are the most suitable times for cuttings. Cuttings root most easily when the temperature is between 5°C and 15°C. For cuttings in protected conditions, vermiculite can be chosen as the cutting substrate, and roots will form in just over 20 days at 10-15°C. For autumn cuttings in the open field, ordinary garden soil can be used as the cutting substrate. The suitable rooting soil temperature is 5-15°C. After inserting the cuttings, firm the substrate to prevent wind from shaking the cuttings. Water thoroughly once, and normal growth and flowering can begin the following spring. Cutting density ranges from 100-500 plants per sq m, depending on the purpose. Field-grown seedlings can be transplanted 3 months after emergence, and plug tray seedlings can be transplanted after 2 months. Cutting-propagated seedlings can be transplanted 40 days after cutting.
Cultivation management. Sweet William prefers slightly alkaline soil, with a pH of 7.5-8.7 being suitable. Sweet William is cold-resistant and drought-resistant, dislikes heat and waterlogging, and likes full sunlight; in summer, partial shade is preferable. It likes high, dry and well-ventilated sites. Apart from this, it has no excessive requirements for soil, but fertile, loose, well-drained calcareous loam is best. In northern regions, it can be planted in courtyards and fields. Sweet William has low requirements for fertilizer and water; before sowing, applying farmyard manure or compound fertilizer just once can meet its needs for the entire growth cycle. When it is excessively dry, water moderately. In most regions, it can grow and bloom normally relying on natural rainfall, as long as water and fertilizer are not excessive; a little less is not a big problem.
When planting out, the spacing between plants and rows is 35 cm x 45 cm. After planting out, apply fertilizer once every 3 weeks and pinch back 3-4 times to encourage more branching. After flowering, promptly cut off spent flowers, apply fertilizer once every half month, and it can bloom again after September. Because the capsules ripen unevenly, harvest in batches. During breeding, varieties in the mother plant cutting garden should be isolated to prevent variety mixing.
Post-flowering management. After flowering, promptly cut off the flowering stems to maintain the groundcover effect of Sweet William. Where growth is too dense, thin out some branches and leaves or entire seedlings to improve ventilation and light penetration. Rejuvenated cutting-propagated plants can generally bloom for 1-2 years, while seed-propagated plants can bloom continuously for 3-5 years. Generally, old plants are rejuvenated when the base loses the ability to sprout new shoots. Dig out the old plants and replant with cuttings or seeds. For large-scale greening, renewal by sowing is relatively feasible.
Pest and disease control. In rainy summer seasons, Sweet William sometimes develops wilt disease. This disease is mainly prevented. Keep the terrain level and high and dry, so water does not accumulate after rain. Even if individual plants develop wilt disease, it will not affect the overall effect of the group, and there is no need to specifically treat the disease. In high-temperature seasons, leaf pests may also occur, boring holes in the leaves. This is also not important, and there is no need to specifically control the pests, as it will not cause major damage.