The Gladiole (Gladiolus), also called sword lily, belongs to the family of the irises (Iridaceae). There are over 200 game species, which are spread from Southern Europe over Near East to Africa. The species with the most magnificent flowers come from South Africa. In southern the United States, one single species is native with the marsh- Gladiolus palustris. It is strictly protected because of its low occurrence – it can only be found in a few locations on moor meadows with alternating humidity and humus-rich, calcareous soil.
Appearance and growth
While the game species and forms rarely grow higher than 60 centimeters, the hybrids can grow up to 150 centimeters on good soils. All Gladiolus have parallel, sword-like leaves – hence the botanical genus name (lat. “gladius” for sword). As wintering organs they form tubers into which they retreat after flowering. So they can survive in inhospitable habitats such as the South African steppe. The large flowers of the frost-sensitive tuber plants appear from the end of June to September, depending on the planting season. They stand in spike-like inflorescences and are irregularly structured with only one vertical plane of symmetry. There are varieties in almost every flower color from white to green and yellow, orange, red, violet to smoke grey and brown.
Location and soil
Gladiolus prefer a deep and permeable soil. The substrate should be fresh to slightly moist and very nutritious. On heavy, impermeable soils, a drainage layer of coarse sand is indispensable. They are also true sun worshippers who should be given a sunny and sheltered place in the garden.
Gladiolus are planted at the earliest at the end of April, so that the frost-sensitive shoots only come to the surface after the ice saints. If you want earlier flowers, you can also prefer them in pots and plant them in a bed. Make sure that the layer of soil above the tubers is at least twice as high as their diameter – this is the only way to ensure that the growing flower stems are sufficiently stable. To extend the flowering period, you can plant the tubers from the end of April to the end of May at intervals of one week each. Note that Gladiolus, similar to roses, should only be planted at the same location every six years.
Cut withered inflorescences early to prevent seed formation. As gladioluses are in need of nutrients, you should sprinkle the planting areas with ripe compost and horn flour immediately after the tubers have been inserted. Gladioluses can be cut as soon as the first one or two flowers have opened. Be sure to leave four to five leaves on the stem so that a new tuber can develop.
Wintering or winter protection
In autumn, after the first night frost, the tubers are dug out, freed from larger lumps of earth and wrapped in wooden crates with coarse sand. A cool, frost-free cellar with high humidity is the ideal place for winter storage.
Like dahlias, Gladiolus are popular tuber plants, which were already ubiquitous in farmer gardens in the past. They can be integrated into any flower and shrub bed, provided the location is sunny and the soil is well permeable. Due to their small space requirement, they are also ideal for narrow planting strips at the house and on the terrace. Depending on the preferred habitat, the game species feel at home in the rock garden or in the swamp zone of the garden pond. Gladiolus can also be integrated into modern prairie gardens, but small flowered botanical species and varieties are preferred. Precious and butterfly gladiolas can also be cultivated well in planters and are excellent cut flowers. Always plant sword lilies in small and large groups of 5 to 15 tubers. If possible, choose tone-in-tone combinations or choose two matching flower colours, otherwise the bed will quickly become too colourful.
Important species and varieties
Numerous garden hybrids have been created by crossing different game species, most of which are listed under the botanical name Gladiolus x hortulanus. A distinction is made between the monochromatic precious gladiolas, the butterfly gladiolus with mostly multicoloured flowers and the baby and wild gladiolas, which are predominantly small species and varieties that have undergone little breeding modification. Lady Godiva’ is white with a green pattern. Of the small varieties, each with a maximum height of 50 centimeters, ‘Nymph’ (white, red spotted), ‘Guernsey Glory’ (dark violet, red tips and white spots) and ‘Atom’ (red with white border) have proved their worth.
Division is the simplest and most promising method to multiply Gladiolus. Most varieties readily form daughter tubers on loose soils, which are usually connected to the mother tubers by short runners. You simply cut them off when you pick up the plants in autumn, plant the smaller tubers right away in coarse-grained growing soil and cultivate them throughout the winter in a bright, frost-free place. The wild species can also be propagated by seeds – but it takes several years before they flower for the first time.
Diseases and pests
They tend to rot tubers and stems, especially on heavy, moist soils and in wet and cold weather, caused by various fungal pathogens such as Fusarium and Sclerotina. Certain bacteria can also trigger these diseases. Leaf spot diseases also occur. Gladiolus experts recommend removing infected plants immediately and subjecting the other tubers to hot water treatment at 53 degrees Celsius for half an hour when wintering in order to kill possible pathogens. Then place them in cold water for a few minutes and let them dry well until they are stored.