Green gardening: growing gladioli

Easy to grow in almost any garden, gladioli make a splash of summer colour in a border, are long-lasting cut flowers, and are inexpensive enough that you do not have to store them over winter if you do not want to.  Follow these guidelines to learn how to properly care for your gladioli.

Gladioli grow from corms, which are swollen stem bases. The corm provides the energy to produce the shoot and flower. During the growing season, the new stem base swells with stored food and becomes a new corm sitting on top of the shrivelled old one. There are several thousand named varieties of gladiolus, with new ones being introduced each year.

Visit the North American Gladiolus Council website for more information, pictures of modern varieties, and the addresses of gladiolus specialists near you.

Gladioli are not fussy about the soil, provided it is well drained. A heavy, clay soil should be lightened by adding compost or sharp sand. Groups planted in a border need little special preparation ahead of time, but for those to be planted in a cutting garden, the soil should be dug the previous fall to at least 20 centimetres (eight inches) deep.

1. Rake the area level in spring as soon as the soil is dry enough to work. Gladioli grow best in a soil with a pH of 6.5 — slightly acidic, but they will still grow and flower where the pH is 7.5. The only stipulation on the site is that it must be in full sun. Gladioli do not grow well in partial shade.
2. Plant gladioli from spring to early summer, keeping in mind the days to flowering and the local average first frost date for later plantings. The first plantings can be made about 10 days before the average last frost date, with successive plantings every 10 to 14 days after that. If the first plantings are showing through the soil and there is a frost warning, the small shoots are easy to protect.
3. Small groups, planted in an existing border, can be planted with a trowel, but in a cutting garden, where a quantity of corms will be planted, it is easier to make a narrow trench and plant them in a row. In both cases, add a little bone meal to the base of the hole or trench and scratch it into the soil.
4. For large corms, plant them 15 centimetres (six inches) deep; plant medium-sized corms 11 centimetres (five inches) deep and small ones eight centimetres (three inches) deep, measured from the bottom of the hole to soil level. If planted in rows, leave at least 30 centimetres (12 inches) between the rows for ease of cutting later.

• Mulch with chopped straw or well-rotted leaves to suppress weed growth and conserve moisture.
• Water as needed since gladioli need adequate moisture.
• In a border, surrounded by other plants, staking is seldom necessary, but if grown in rows for cutting, support will probably be needed. A stake at each end of the row, with a string run down each side of the plants, will be sufficient.
• Alternatively, each individual plant can be tied to a single bamboo cane.
• Plants not used for cut flowers should have their old spikes removed once they fade so that energy is not used for seed production that should go into forming next years corm.

Follow these guidelines to ensure your gladioli grow strong and healthy.