Detailed Explanation of Gladiolus Planting Methods and Technical Key Points
Gladiolus, also known as sword lily, corn flag, and ten-variety brocade, is a member of the Iridaceae family, genus Gladiolus. It originated in southern Africa and the Mediterranean region, and is widely cultivated in North America, Western European countries, Japan, and various parts of China.
Propagation Methods
Gladiolus is mainly propagated by corm division. The method is to plant well-developed large corms (about 5cm in diameter) individually in a seedbed from April to May, with a plant spacing of 15cm and a soil cover of about 6-10cm, then firm the soil and water to cultivate. They can bloom from July to August, taking about 100-120 days. Alternatively, a batch can be planted every 10 days from mid-April to late July, so that flowers are produced continuously from July to October. After flowering, the underground corm shrinks, and 1-3 new corms and several small corms form above the mother corm. Corms with a diameter of 2cm (cormels) continue to be planted in seedbeds in spring and cultivated for 2-3 years to develop into large corms that serve as planting stock.
To accelerate propagation speed, methods such as corm cutting, seed sowing, and tissue culture can also be used. The corm cutting method involves cutting the corm before planting, longitudinally cutting the planting corm into 2 or 4 pieces so that each piece has at least 1 bud and part of the basal plate. The cut surfaces are coated with plant ash or charcoal powder to prevent rot, and planting is done after they dry, without prolonged storage.
The seed sowing method is generally used when breeding new varieties. Seeds are collected in summer and autumn and sown immediately after collection, which gives a higher germination rate. The seedlings are moved into a greenhouse to overwinter, then transplanted to open ground the following spring for cultivation, and some plants will flower in summer. Alternatively, after collecting seeds, they can be dried and stored until the following spring for sowing and cultivation; the small seedlings are dug up in autumn and stored, then planted the following spring, and some will flower in summer.
There are serious problems of variety mixing and quality degeneration in gladiolus corm propagation. To improve corm quality and prevent variety degeneration, tissue culture can be used periodically for virus elimination, rejuvenation, and high-quality propagation of gladiolus. The method is to take lateral buds from flower stems or corms, strip off the green leaf sheaths, remove flower buds, disinfect them, and use them as explants for inoculation on culture medium for tissue culture. Corm formation begins after about 60 days, and planting corms can be harvested in 4-6 months.
Gladiolus Planting Methods
The planting bed surface is 5-10 cm high and 1 m wide; flat beds can be used in dry areas. Plant density should be appropriate, generally between 13,000 and 27,000 plants per 667 sq m. The planting depth of gladiolus corms is adjusted according to corm size, soil texture, cultivation purpose, and cultivation season.
Generally, the soil cover is 8-10 cm. In early spring and winter, when soil temperature is low, shallow planting is suitable, with a soil cover of 5-10 cm; in summer, when temperatures are high, deep planting is suitable, with a soil cover of 12-14 cm. Usually, the larger the corm, the deeper the planting; where the soil tends to be clayey, plant slightly shallower; where the soil is obviously sandy, plant slightly deeper; when the main purpose is harvesting new corms, plant shallowly, which benefits new corm growth but makes plants prone to lodging and is unfavorable for flower stem growth and development, with poorer drought resistance. For gladiolus plants used for commercial fresh cut flowers, appropriate deep planting should be used during planting to prevent lodging and cormel growth, and stakes should be inserted around the planting bed with ropes strung around them, but this results in fewer new corms and fewer cormels.
Watering
After gladiolus corms are planted, if the soil is dry, irrigation should be carried out to promote rapid rooting of the corms. During the growth period from the 3rd leaf to the 6th-7th leaf, which is the stage of floret primordium formation (3-leaf stage) and also the critical period when the mother corm roots begin to die and the new corm grows new roots, special attention should be paid to water supply, combined with management practices such as loosening the soil, weeding, and topdressing.
Light and Shading
The most suitable temperature for gladiolus growth and development generally does not exceed 27°C, so in summer high temperatures, attention should be paid to ventilation and shading to avoid plant aging and degeneration caused by excessively high temperatures.
Fertilizing Gladiolus
Gladiolus likes fertile soil, but fertilizer should not be applied excessively. During the growth process of gladiolus, fertilizer can be applied multiple times, generally divided into base fertilizer before planting and 3 topdressings during key growth periods. The base fertilizer is mainly organic fertilizer; fully decomposed organic fertilizer can improve the physical and chemical properties of the soil, adjust soil structure, make the soil loose, improve water permeability and water retention, and promote good root growth. Even more advantageous is the slow-release and long-lasting nature of organic fertilizer, which can provide nutrient supply for the entire growth cycle of the plant. When applying base fertilizer, some quick-acting chemical fertilizers can be used together, but should not be applied in large amounts.
Fertilization should be carried out according to specific conditions such as cultivation type and purpose, soil type and fertility, total soil salt content, and plant growth stage. Because gladiolus is sensitive to soil salinity and fluoride and chloride content, attention should be paid to the choice of fertilizer types. Use tripolyphosphate as little as possible (it easily contains high concentrations of fluoride) and replace it with other phosphate fertilizers, which can effectively avoid leaf tip scorch. Topdressing can be carried out by combining root fertilization and foliar fertilization, and combined with irrigation, to fully exert fertilizer efficiency. Chemical fertilizers that can be used for topdressing include: ammonium nitrate, potassium nitrate, superphosphate, monopotassium phosphate, ammonium sulfate, potassium sulfate, urea, etc. Use potassium chloride and fluorine-containing phosphate fertilizers as little as possible.
The suitable time and types of fertilization are determined according to growth and development characteristics. The first time is after the plant has 2 expanded leaves; the fertilizer is mainly nitrogen and potassium fertilizer. This is the floret differentiation stage, and the nutrients in the originally planted corm have been largely consumed. If fertilizer and water are insufficient at this time, the number of florets in the inflorescence will decrease, affecting the commercial value of fresh cut flowers. The second time is after the 4-leaf stage, when the flower stem begins to gradually elongate and individual florets develop faster; the fertilizer is mainly phosphorus and potassium fertilizer, to promote thick and strong flower stems, large and brightly colored flowers, and long vase life after cutting. The third time is after flowering, which is the growth and development period of new corms and cormels, requiring large amounts of nutrients to promote full development of new corms. The degree of corm plumpness and the number of cormels will have a relatively large impact on the next year's cut flower production and expanded propagation, and the fertilizer is still mainly phosphorus and potassium fertilizer.