How to Grow Gladiolus? A Detailed Guide to the Latest Cultivation Methods
Gladiolus is a light-loving long-day plant that cannot tolerate cold or freezing. In summer it prefers a cool climate and cannot stand 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 where waterlogging occurs. In the Northeast and North China regions, summer growth 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 is mainly propagated by dividing the corms. The new corms bloom the following year. To speed up propagation, the corms can also be cut into sections, each of which must have a bud and a root-forming part. The cut surfaces are coated with plant ash and planted after drying slightly. When breeding new varieties, seed propagation is often used. Seeds harvested in autumn are sown immediately and have a high germination rate. In winter the seedlings are moved into a greenhouse for cultivation, and in the following spring they are transplanted outdoors in separate plots. With intensive management, some seedlings can bloom in autumn.
Field Management
To grow gladiolus, choose a sunny, well-drained sandy loam rich in humus. Although it can grow and bloom in clay soil, the development of replacement corms is poor and few small corms form beneath the large corms. Before planting, apply sufficient base fertilizer to the soil; fertilizers rich in phosphorus and potassium are best. Planting depth varies with soil properties and corm size, generally 5-10 cm, with a spacing of 15-25 cm between plants and rows. Apply top-dressing 3 times during the growing period. The first is after two leaves have unfolded, to promote the growth of shoots and leaves; the second is when the stems of 4 leaves elongate and buds form, to promote thick, sturdy flower spikes and large blooms; the third is after flowering, to promote the development of replacement corms. Sunlight during the growing period favors flower bud differentiation and development. In summer, if drought occurs, irrigate thoroughly, and during the rainy season pay attention to drainage and irrigation.
Key Cultivation 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 to 1.5 m wide. Fertilization should balance nitrogen, phosphorus and potassium. Since gladiolus is a shallow-rooted plant, fertilizer should be applied shallowly. Top-dressing is applied at the two-true-leaf stage (after flower bud differentiation) and at the ear-emergence stage, once with dilute manure water plus urea, once heavily with potassium fertilizer at the mid-stage, and in the later stage attention should be paid to controlling nitrogen to prevent excessive vegetative growth and lodging. For plots mainly producing seed corms, potassium fertilizer should be the main addition.
2. Corm selection and treatment: After deciding on the cultivar, pay attention to selecting corms. When selecting, make sure the cultivars are not mixed, and choose seed corms that are free of pests and diseases and have undamaged bud points. Before planting, soak the graded corms in water for 15 minutes, then disinfect them by soaking for half an hour in 0.1% mercuric chloride or 80 times diluted formalin solution. After removal, rinse them clean before planting.
3. Planting time: Under natural conditions, planting is generally done in April to May, when the soil temperature is around 10°C. For year-round production, the time should be determined according to the different flowering supply periods. Under conditions where temperature and light are guaranteed, those required to reach market before New Year's Day should be planted in early September; those for the Spring Festival market can be planted in late September; those supplying cut flowers in early spring can be planted from late November to late December. For flowering from late May to early June, sprouts can be forced in early February and planted outdoors in early April; for National Day flowering, planting can be done from early June to mid-July.
4. Breaking dormancy: The corms remain dormant for about 3 months under low-temperature conditions. If earlier planting is needed, treat them first at a high temperature of 35°C for 15-20 days, then 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; excessive humidity easily causes the corms to rot.
5. Planting specifications: These vary with the plant type of the cultivar. Large plant types are spaced 20 cm apart, while medium and small plant types are spaced 10-15 cm apart. Planting depth is generally 3 cm to 10 cm. To prevent lodging, when planting the corms, place 2 layers of 20 cm square nylon netting on the planting bed in advance; later, as the plants grow taller, tighten the support lines layer by layer to prevent the plants from lodging and the flower stems from bending.