How to grow gladiolus? Detailed growing methods and precautions
Gladiolus is a light-loving long-day plant that cannot tolerate cold or freezing. It prefers cool summer climates and does not tolerate excessive heat. The corms begin to sprout at 4-5°C; growth is best at 20-25°C. It prefers fertile, deep sandy soil and requires good drainage; it should not be planted in heavy clay soil prone to waterlogging. Summer growth in Northeast and North China is better than in Guangzhou and Shanghai. In Shanghai it can overwinter safely outdoors, while in the north the corms must be dug up and stored indoors for the winter.
Propagation methods
Gladiolus propagation is mainly by corm division. New corms bloom the following year. To speed up propagation, the corms can also be cut into sections, each piece must have a bud and a root-forming part; the cut surface is coated with plant ash, dried slightly, and then planted. When breeding new varieties, seed propagation is mostly used. Seeds collected in autumn are sown immediately and have a high germination rate; in winter the seedlings are moved into a greenhouse for cultivation, and the next spring they are transplanted outdoors in separate plots with intensified management. By autumn some seedlings may bloom.
Field management
For growing gladiolus, choose a sunny, well-drained sandy loam rich in humus; although it can grow and bloom in clay soil, the renewal corms develop poorly and few small corms form under the large corms. Before planting, apply enough base fertilizer to the soil, preferably a base fertilizer rich in phosphorus and potassium. Planting depth varies with soil properties and corm size, generally 5-10 cm, with a plant and row spacing of 15-25 cm. Apply topdressing 3 times during the growing period. The first is after two leaves have unfolded, to promote bud, stem and leaf growth; the second is when the stems of 4-leaf plants elongate and form buds, to promote thick flower stalks and large flowers; the third is after flowering, to promote renewal corm development. Sunlight during the growing period favors flower bud differentiation and development. In summer, if drought occurs, irrigate fully, and at the same time pay attention to drainage and irrigation during the rainy season.
Cultivation key points
1. Land preparation and fertilization: For planting gladiolus, sandy loam should be chosen, with a deep, loose, well-drained soil layer, and waterlogging must be avoided. Make raised beds 20 cm high and 1 m-1.5 m wide. Fertilization should balance nitrogen, phosphorus and potassium. Since gladiolus is a shallow-rooted plant, fertilizer should be applied shallowly. Topdressing is applied respectively at the two true-leaf stage (after flower bud differentiation) and the heading stage, applying once diluted manure water plus urea, applying a heavy potassium fertilizer once in the middle period, and paying attention to controlling nitrogen in the later period to avoid excessive vegetative growth and lodging. For plots mainly producing planting corms, increasing potassium fertilizer should be the main approach.
2. Corm selection and treatment: After determining the cultivar to grow, pay attention to selecting corms. When selecting, make sure the varieties are not mixed and choose seed corms free of pests and diseases with undamaged buds. Before planting, soak the graded corms in water for 15 minutes, then soak them for half an hour in 0.1% mercuric chloride or 80-times diluted formalin for disinfection. After removal, rinse them clean before planting.
3. Planting time: Under natural conditions, planting is generally done in April-May when the soil temperature is about 10°C. For year-round production, it should be determined according to different flowering supply periods. Under conditions with guaranteed temperature and light, those required to reach the market before New Year's Day should be planted in early September, those for sale during the Spring Festival can be planted in late September, and those for cut flowers supplied in early spring can be planted from late November to late December. For flowering from late May to early June, germination can be forced in early February and outdoor planting done in early April; for National Day flowering, planting can be done from early June to mid-July.
4. Breaking dormancy: Under low-temperature conditions, corms remain dormant continuously for about 3 months. If earlier planting is needed, they can first be treated at a high temperature of 35°C for 15-20 days, then treated at a low temperature of 2°C-3°C for 20 days to break dormancy. During this period, however, the corms should be kept dry, as excessive humidity easily causes corm rot.
5. Planting spacing: This varies with the plant type of different varieties. Large plant types are spaced 20 cm apart, while small and medium plant types are spaced 10-15 cm apart. Planting depth is generally 3 cm-10 cm. To prevent lodging, when planting the corms, pre-place 2 layers of 20 cm square nylon netting on the planting bed, and later, as the plants grow taller, tighten the support layer by layer to prevent the plants from lodging and the flower stems from bending.