Family: Iridaceae

There are about 180 species of gladioli coming originally from various parts of Africa, Europe and the Middle East. Their name derives from the Latin gladius, a sword, which refers to the shape of their leaves. Gladioli are grown from corms, the compressed base of the stems, which produce two or three leaves and usually a one-sided flower spike. However, many hybrids have been developed which vary enormously in size, colour and the arrangement of the blooms on the flower spike, the most well-known being the large-flowering types. Gladioli are not as easy to grow and care for as many other flowering plants as they may need regular spraying, but they are still very popular because they make a striking display in the garden and provide excellent cut flowers. They can also be grown in pots.

Species

G. communis subsp. byzantinus, zone 7, originating from the Mediterranean, produces red or reddish purple flowers, with faint white markings. The leaves are about 30 cm (12 in) long and the flower spikes nearly three times as long. A white form is also available.

G. x colvillei flowers in colours of white, deep pink or yellow and has given rise to many forms which also flower in late spring.

G. tris­tis produces highly perfumed, pale yellow flow­ers, sometimes with purple bands on the upper petals. The flower stems are shorter, to 60 cm (24 in), and the leaves are quite slender. This species may be left undisturbed for some years. Species gladioli are becoming readily available, but most varieties grown are cultivars and hybrids.

Cultivation

Gladioli must be grown in a posi­tion that receives full sun. In milder areas, plant the corms in late winter; in cooler zones, plant in spring to early summer. They require very good drainage, so if the soil is heavy, build tip the bed about 15 cm (6 in) above normal soil level and lighten the soil by adding sand. If the soil is very acid, apply a dressing of lime or dolomite at the rate of 60-120 g per square metre (2-4 oz per square yard). Compost or decayed cow manure may be added, as well as commercial rose fertilizer or other complete plant food.

Plant corms in clumps about 8-10 cm (3-4 in) deep and 15 cm (6 in) apart. Several corms of the same variety look impres­sive when planted together. Water thoroughly and mulch after planting. In some areas, gladi­olus thrips are a problem every season as they damage the foliage and flowers with their rasp­ing and sucking action. Spraying with a regis­tered pesticide may therefore be necessary.

Flowers should be ready for picking 11 to 14 weeks after planting, though cold weather can slow growth and some varieties are slower to mature than others. Cut flowers just as the second bud on the spike is starting to open. Cut the stem, leaving as many leaves as possible. After the flowers have been cut, continue to give the plant the usual care. When the foliage yellows and dies, dig out the plants carefully and cut the remnants of withered leaves back to within two centimetres (about an inch) of the new corm, which will have formed above the old one.

Dry corms in a warm, airy place, then clean off the remains of the old corms, dust with derris or other insecticidal dust and store in paper bags, labelled with their colours. When the new planting season comes around, any small cormlets present around the base of the new corms should be set out about 5 cm (2 in) apart in a separate area. The following year, the cormlets, after having been lifted and stored over winter, can be again planted out, spaced around 10 cm (4 in) apart. Cormlets should come true to colour and type.

Climate

Zone 9 for most species.