The Gladiolus - The Ultimate Cut Flower
The Gladiolus is a perennial bulbous flowering plant of the iris family. 'Gladiolus' comes from the Latin gladius meaning a sword and is sometimes called the sword lily. There are around 260 species with about 170 native to southern Africa and 76 to tropical Africa. About ten species are endemic to Eurasia. The blooms of wild gladioli vary from very small to about 40mm across with one to several blooms on each inflorescence. Genetic manipulation and selective breeding has resulted in the myriad varieties now available.
The gladiolus is semi-hardy in temperate climates and grows from rounded corms which are enveloped in several layers of fibrous tissue. The stems consist of narrow, sword-shaped leaves enclosed in a sheath. The fragrant, large flowers are one-sided and funnel-shaped. Pink, red, light purple, cream flowers are common with various contrasting markings. The gladiolus is an important food plant for the larvae of some butterfly species.
Gladioli are grown mainly as cut flowers. However they also bring colour and interest to the garden. The large spikes are not so widely used now but short-stemmed spikes are useful in ikebana, low-table arrangements and in mixed troughs and vases. Due to their height, the flower spikes of cultivated forms are often broken off under windy conditions. The species has been extensively hybridized and there is a huge range of ornamental flower colours. The main hybrid groups are Grandifloras, Primulines and Nanus.
You can enjoy spikes of gladioli in the garden and pick them for cut flowers when the lower flowers have finished. Unopened flowers will continue to bloom in water for a week or so.
In the garden, gladioli look better in clumps than in rows. Seven or eight bulbs make a natural looking and imposing clump. Because the clumps will look a little dreary between flowering and lifting time, it is a good idea to grow other plants between the clumps. By doing this, you can keep a continuity of colour too.
Gladioli can be started where dahlias or chrysanthemums have been removed. They will also look great sandwiched between drifts of spring bulbs or low-growing annuals. Later the annuals can be replaced with phlox, petunias or other summer annuals that will begin to bloom soon after the gladioli finish in November.
Don't plant tall plants close enough to shade the gladioli as they will need all the sun they can get. Zinnias, asters or even dahlias are suitable as the gladioli will generally have finished flowering before the other tall plants start to make any appreciable height.
The time of flowering depends on the time of planting. Providing the corms have had about six months to mature after the previous flowering, it is usually about 90 days from planting to flowering. Different varieties also flower at different times as a mix of varieties in each clump will mean prolonged displays.
In temperate climates, corms are usually lifted in autumn and stored over winter away from frost. In the southern hemisphere, peak flowering can be achieved around Christmas if plants are delayed until mid-September. Some of the species from Europe are much hardier and will withstand temperatures to -16oF/-27oC. If the winters are sufficiently dry, the corms can be left in the ground. The small 'Nanus' hybrids and those from the high African altitudes can also be left in the ground.
In hot climates, avoid plantings which would result in flowering in very hot weather as this will result in scorched blooms. Commercial growers may retard bulbs by placing them in cold storage so that they will flower out of the normal season.
Technically gladioli grow from corms which are included in the loose term of 'bulbs'. Unlike true bulbs, the flower of the gladiolus has not already formed in the 'bulb' the previous season. The flower spike forms as growth progresses so good growing conditions mean larger spikes and better flowers. Plenty of sunlight and a rich well-drained soil are preferred.
For best results, make a hole about 6 inches in depth and a foot across. Sprinkle two tablespoons of complete plant food over the base of the hole and add an inch or so of well-rotted compost. Fork the plant food and compost into the base of the hole, and cover with an inch of untreated soil to protect the corms from coming into direct contact with the fertiliser. Set the corms about 3 inches apart in a rough circle round the edge of the hole ie about 7 corms to a 10 inch diameter hole.
In windy areas, stakes will be needed for the plants. Drive the stakes in first so you don't damage the corms. It is generally recommended that plants be set about 4 inches from the surface to the base of corms in average loamy soil. Plant corms a little shallower in heavy clay and at a depth of up to 6 inches in sand. Water sparingly until the foliage breaks the surface but don't let the soil dry completely. After the plants have pushed through, circle each clump with a good handful of complete plant food or superphosphate. Keep the superphosphate a few inches away from the foliage. Scratch the super into the surface and water well as this will help in flower formation. Don't feed again until the plants reach a five leaf stage. Then feed each fortnight, watering with a complete liquid plant feed. Water thoroughly once a week in dry weather or more often in light sandy soil.
Hill the soil up around the plants to help support the plants in wet and windy conditions. You may need to tie them. Thrips are a persistent pest of gladioli. Spray every fortnight with a complete pest killer to control these. Make sure that that spray reaches all surfaces of the plant. Symptoms of thrip damage are grey flecks towards the base of the foliage. Other symptoms are buds which show colour but which fail to open.
Gladioli can be propagated from cormlets which appear as offsets on the parent corms or from seed. New plants may not flower for several years. Dig up and divide the clumps every few years to keep the plants vigorous.
There are thousands of wonderful gladioli varieties. As stated, they make magnificent indoor flowers and most garden centres will have a good mix of varieties.