How to Grow Gladiolus? A Detailed Guide to the Latest Growing Methods

Gladiolus, also known as sword lily, gladiola, flat-stemmed lily, and ten-pattern brocade, is a perennial herbaceous plant of the genus Gladiolus in the iris family (Iridaceae), with extremely high ornamental value. It can be used in flower baskets, bouquets, and vase arrangements, and can also be used to create flower borders and specialized flower beds; dwarf varieties can be grown in pots for viewing. Along with cut-flower roses, carnations, and gerbera daisies, it is known as one of the “world's four great cut flowers.” Now let's take a look at how to grow gladiolus!

Gladiolus Growing Habits

Gladiolus is a plant that loves warmth, but excessively high temperatures are unfavorable for its growth. It is not cold-tolerant, and the optimum growing temperature is 20-25°C. The corms can sprout when the soil temperature is above 5°C. It is a typical long-day plant; long daylight promotes flower bud differentiation, and insufficient light will reduce the number of blooms. However, after flower bud differentiation, short daylight favors bud formation and earlier flowering. The bulbs of summer-flowering varieties must be stored indoors over winter, and the indoor temperature must not be lower than 0°C. Fertile sandy loam is the ideal cultivation soil, with a pH value not exceeding 7. It is especially fond of fertilizer; phosphorus fertilizer can improve flower quality, and potassium fertilizer helps improve corm quality and increase the number of cormels.

Gladiolus Propagation Methods

1. Corm division: After one year of cultivation, one mother corm of gladiolus will produce 1-2 commercial corms and many cormels. Medium and large corms are planted by the furrow dibbling method, small corms by the furrow broadcasting method, and cormels mostly by the direct broadcasting method. Before planting, apply sufficient basal fertilizer, but be careful that the fertilizer does not come into direct contact with the corms. After sowing, pay attention to water management; do not water until the soil is dry before emergence.

2. Corm cutting: For certain rare gladiolus varieties that need to rapidly expand their propagation coefficient, plump and full commercial corms can be cut into 2-4 pieces, each piece must retain part of the basal plate and a complete, plump bud, and these are used for cormel propagation. To prevent the seed corms from rotting, the cut surfaces should be coated with charcoal powder or plant ash and planted immediately.

3. Tissue culture: Long-term asexual propagation of gladiolus leads to quite serious variety mixing and degeneration, so regular tissue culture must be carried out for virus elimination and rejuvenation. Both petals and lateral buds can be used as explants. After disinfection and inoculation, they can be cultured at 25°C and 2000 lux. Through induction, subculture, and rooting culture, plantlets are obtained. Continued culture of the plantlets yields test-tube cormels; after hardening and two years of planting, the test-tube corms grow into mother corms.

Gladiolus Growing Methods

1. Soil: Gladiolus prefers fertile, deep sandy soil and requires good drainage. Well-drained sandy sloping soil is most suitable, with a pH of 5.6-6.5 being ideal. It should not be planted in heavy clay soil or places prone to waterlogging.

2. Watering: Gladiolus is a flower that needs a lot of water. Timely watering and keeping the soil moist are important measures to encourage more blooming. In hot, high-temperature weather, spray promptly to increase humidity and lower the temperature, and pay attention to drainage after rain.

3. Temperature: The optimum growing temperature for gladiolus is 20-25°C during the day and 10-15°C at night. Growth is hindered when the temperature is above 27°C, and petals are easily scorched; below 10°C, growth is slow.

4. Sunlight: Gladiolus is not shade-tolerant and is a long-day plant. The most suitable condition is 16 hours of light per day. Cut-flower varieties are greatly affected by light; sufficient sunshine makes them grow robustly with strong stress resistance and vivid, long-lasting flower colors. However, in hot summers, strong direct sunlight should also be avoided.

5. Fertilizing: Gladiolus is a shallow-rooted plant, so fertilizer should be applied shallowly. Fertilization should balance nitrogen, phosphorus, and potassium. Topdressing is done respectively at the two-true-leaf stage (after flower bud differentiation) and the heading stage, applying dilute manure water plus urea once; in the middle stage, apply a heavy dose of potassium fertilizer once; in the later stage, be careful to control nitrogen to prevent excessive vegetative growth and lodging. For plots mainly producing seed corms, additional potassium fertilizer should be the main focus.

Gladiolus Pest and Disease Control

1. Mosaic disease

[Symptoms] Mosaic disease mainly infects leaves, and also infects flower organs and other parts. In the early stage of the disease, chlorotic angular spots and round spots appear on the leaves. Because the spread of the lesions is restricted by leaf veins, they are mostly polygonal, and eventually turn brown; diseased leaves become yellowed and twisted. Affected plants are stunted with short flower spikes, and severely affected plants cannot produce flower spikes. In early summer, symptoms on new leaves are particularly obvious; in midsummer, symptoms are not obvious, showing a phenomenon of latent symptoms.

[Control] Strengthen quarantine to control disease occurrence. Test seed corms, select virus-free corms for planting, and uniformly destroy virus-carrying corms to reduce re-infection of flowers. Promptly remove diseased plants from flower beds to prevent mutual infection. When the disease occurs, spray the leaf surfaces with 58% mancozeb wettable powder at 500 times dilution, or 75% chlorothalonil wettable powder or 50% carbendazim wettable powder at 1000 times dilution, once every 7 days, generally 3-4 sprays are sufficient.

2. Dry rot

[Symptoms] Dry rot mainly harms the corms, leaves, flowers, and roots of the plant. When the plant is affected, the tips of the outer leaves first begin to yellow, then it spreads to the inner leaves, and finally the plant withers.

[Control] Try to avoid continuous cropping in the same flower bed, avoid applying too much nitrogen fertilizer, and appropriately increase the use of phosphorus and potassium fertilizers. Before planting, corms can be soaked in 50% carbendazim at 500 times dilution for 30 minutes. In the early stage of the disease, spray the leaf surfaces with 50% zineb at 1000 times dilution once every 7 days, generally 3 sprays.

3. Leaf spot

[Symptoms] The pathogen can infect leaves and corms. After leaf infection, small brown spots appear, which gradually enlarge and deepen in color, eventually causing the leaves to wither. After corm infection, the plants that grow are stunted and may even fail to bloom.

[Control] Practice crop rotation; severely affected areas must be rotated to reduce disease inoculum. For corm treatment, corms should be dried after harvest and stored dry to prevent rot. Before planting, they can be disinfected with 50% thiram and then sown. For chemical control, spray with 75% chlorothalonil at 800 times dilution or treat with 65% zineb.

4. Scab

[Symptoms] Scab mainly damages corms, and sometimes also damages leaves. After corm infection, water-soaked round lesions appear, and the color gradually deepens from gray to dark brown. The lesion edges are raised and the centers are sunken. After leaf infection, water-soaked soft rot occurs.

[Control] Use disease-resistant cultivation, choose a high, dry, and well-ventilated environment, pay attention to drainage, practice crop rotation, and maintain field sanitation. This disease can only be prevented, not cured; there is no specific effective medication.

5. Fusarium wilt

[Symptoms] Fusarium wilt mainly occurs on corms, and sometimes also infects leaves and flowers. In the early stage, small reddish-brown spots appear, which gradually enlarge, become sunken and shrunken, and may even rot, then white thread-like bodies grow. After affected corms are planted, in mild cases growth is poor and flowers are deformed; in severe cases they fail to sprout or the seedlings die.

[Control] Use double selection and disinfection of corms. After harvest, grade them and remove diseased corms. Soak seed corms in 0.5% formalin solution for 2h, wash with warm water, dry, and refrigerate until the following spring. At planting time, carry out a second selection, disinfect with 5% carbendazim at 500 times dilution, and then sow. Avoid continuous cropping.

6. Gray mold

[Symptoms] Gray mold often occurs on leaves and petals. In the early stage, small gray-brown spots often appear, which gradually enlarge, and gray mold appears on the surface of the lesions.

[Control] Store corms properly, keep the environment dry, keep the cultivation environment well-ventilated and well-lit, and ensure good drainage. For chemical control, spraying 80% zineb wettable powder at 500-700 times dilution gives good results.

7. Thrips

[Symptoms] Adult and nymph thrips generally hide in leaf axils during the day, and crawl onto the leaf surface at night or on cloudy days to harm the plant. They mainly bite and feed on the plant's leaves, stems, and flowers, causing leaves to discolor and leaving grayish-white dot-like feeding marks and egg-laying marks on the corolla, causing petals to curl.

[Control] Spray with 40% dimethoate emulsifiable concentrate at 1000 times dilution or 80% dichlorvos emulsifiable concentrate at 300 times dilution for control.