A Detailed Guide to Growing Gladiolus in Pots: Methods and Precautions

Gladiolus, whose scientific name is Gladiolus gandavensis, belongs to the Iridaceae family of bulbous plants, with its original species native to South Africa. The flower stem rises above the leaves, the corolla tube is an enlarged funnel shape, and the flower colors include red, yellow, purple, white, blue and other single or bicolor varieties. It is widely cultivated around the world. So, is gladiolus easy to grow? What are the growing methods?

Gladiolus is a sun-loving plant that likes to grow in places with plenty of sunlight, but when planting in summer, note that gladiolus prefers a cool climate in summer and is not tolerant of heat, so never expose it to blazing sun. Gladiolus is not cold-tolerant during growth, so winter planting requires protection from the cold. Its main growing areas are Northeast China, North China, and southern places such as Guangzhou and Shanghai. So, what are the growing methods for gladiolus? What are the precautions?

First, a brief overview of the growing methods for gladiolus, then we will go through soil, environment, watering and so on one by one. Growing gladiolus is actually quite simple; as long as there are 4-5 months of suitable growing time, it can be planted. From planting the corm to flowering, gladiolus takes about 60-120 days (flowering time varies by variety). During growing, one thing to watch is light (plenty of light), and another is watering (avoid waterlogging). Below we will look at the specific growing methods.

Select the corms of gladiolus, choosing small corms from among the flat round corms that are disease-free, spot-free, and have no damage to the sprouting and rooting parts, for cultivation. After planting the corms, water thoroughly once, place in a ventilated, sunny spot, and keep the soil moist.

1) Planting time: In China, the best planting time for gladiolus is spring; it can be planted once the average temperature is above 20°C.

2) Planting depth: The best soil coverage depth for gladiolus is about 10 cm.

3) Planting environment: Whether in pots or in the ground, plenty of light is essential. If there is no good light condition, then it is better to give up growing gladiolus.

4) Temperature requirements: The suitable growing temperature for gladiolus is spring, around 20°C. The corms sprout at 4°C and grow best at 20-25°C. In any area with 4-5 months of growing season in a year, it can be planted in the open ground. When the temperature is above 27°C, growth is hindered and the petals are easily scorched; below 10°C, growth is slow.

4) Soil: Well-drained sandy soil is best, though other soils are also fine as long as drainage is good, because gladiolus is not tolerant of waterlogging and the corms rot easily, so the drainage of the potting soil is especially important. It likes fertile, deep sandy soil and requires good drainage; well-drained sandy slope soil is most suitable, with a pH of 5.6-6.5 being appropriate. It should not be planted in heavy clay soil that easily waterlogs.

5) Light: Gladiolus is not shade-tolerant and is a long-day plant, with 16 hours of light per day being most suitable. Cut-flower varieties are greatly affected by light; with sufficient sunlight they grow strong, have strong resistance, and the flowers are bright and long-lasting. But in hot summer, strong direct sunlight should also be avoided, otherwise the gladiolus leaves will be scorched and scarred.

6) Watering: Overall, less watering is better; the soil should normally be slightly on the dry side, and it should not stay moist for a long time. In the early stage of cultivation, do not water too much; during the growing period, water continuously to keep the potting soil moist; after the flower stem emerges, spray water on the leaves 1-2 times a day to increase air humidity.

7) Fertilizing: Gladiolus has a fairly high demand for fertilizer, especially in pots. Phosphorus and potassium fertilizers are the main ones, and light fertilizer can be applied frequently. Gladiolus is a shallow-rooted plant, so fertilizer should be applied shallowly. Fertilizing should balance nitrogen, phosphorus and potassium. Topdressing is done respectively at the two-true-leaf stage (after flower bud differentiation) and at the earing stage, applying once dilute manure water plus urea; at the middle stage, apply a heavy dose of potassium fertilizer once; at the later stage, control nitrogen to avoid excessive vegetative growth, which causes lodging. For plots mainly producing corms, increasing potassium fertilizer should be the main approach.

Precautions:

1) Light: Before flower bud differentiation, the care environment needs long-day light, which is beneficial for gladiolus flower bud differentiation. Insufficient light will reduce the number of flowers. After flower bud differentiation is complete, short-day light helps the formation of flower buds and earlier flowering.

2) Temperature: Gladiolus likes warmth, dislikes stuffiness, and is not cold-tolerant, so the temperature of the care environment is very important. The optimal temperature for gladiolus growth and development generally does not exceed 27°C, so in high summer temperatures, pay attention to ventilation and shading to avoid excessively high temperatures causing aging and degeneration of plant growth. The optimal suitable temperature is 20-25°C during the day and around 15°C at night.

3) Ventilation: After the gladiolus flowers fade, once the leaves begin to yellow and wither, the corms can be harvested. By this time the old corm has shrunk, a new corm has grown on top, and many small corms have formed around it. Dry these corms and store them in a cool, ventilated place for replanting the following year.

4) Planting time: Gladiolus is suitable for spring planting. Some flower lovers cannot resist planting in autumn, but because gladiolus has the habit of winter dormancy, gladiolus planted in autumn mostly withers before flowering.

5) Preventing corm rot: Do not cut off the leaf cluster before digging. After digging, first tie them in bundles or spread them out to dry, then take the corms for storage. The corms should be spread thinly on multi-layer racks indoors, requiring ventilation and dryness, to prevent freezing damage. If the soil stays wet for a long time, for example, in ground planting with many days of continuous rain, the corms may rot; in potted planting, if too much water is given and the potting soil drains poorly, the corms also rot easily.