Their stems are generally unbranched, producing 1 to 9 narrow, sword-shaped, longitudinal grooved leaves, enclosed in a sheath. The lowest leaf is shortened to a cataphyll. The leaf blades can be plane or cruciform in cross section.
The fragrant flower spikes are large and one-sided, with secund, bisexual flowers, each subtended by 2 leathery, green bracts. The sepals and the petals are almost identical in appearance, and are termed tepals. They are united at their base into a tube-shaped structure. The dorsal tepal is the largest, arching over the three stamens. The outer three tepals are narrower. The perianth is funnel-shaped, with the stamens attached to its base. The style has three filiform, spoon-shaped branches, each expanding towards the apex.
The ovary is 3-locular with oblong or globose capsules, containing many, winged brown, longitudinally dehiscent seeds. In their center must be noticeable the specific pellet like structure which is the real seed without the fine coat. In some seeds this structure is wrinkled and with black color. These seeds are unable to germinate.
These flowers are variously colored, pink to reddish or light purple with white, contrasting markings, or white to cream or orange to red.
The South African species were originally pollinated by long-tongued anthrophorine bees, but some changes in the pollination system have occurred, allowing pollination by sunbirds, noctuid and sphingid moths, long-tongued flies and several others. In the temperate zones of Europe many of the hybrid large flowering sorts of gladiolas can be pollinated by small well-known wasps. Actually, They are not very good pollinators because of the large flowers of the plants and the small size of the wasps. Another insect in this zone which can try some of the nectar of the gladioli is the best-known European Hawk-moth Macroglossum stellatarum which usually pollinates many famous garden flowers like Petunia, Zinnia, Dianthus and others.
Gladioli have been extensively hybridized and a wide range of ornamental flower colours are available from the many varieties. The main hybrid groups have been obtained by crossing between four or five species, followed by selection: Grandiflorus, Primulines and Nanus. They make very good cut flowers. However, due to their height, the cultivated forms frequently tend to fall over in the wind if left on the plant.
The genus Gladiolus has been divided in to many sections. Where possible, the sections have been indicated. Most species, however, are only tentatively placed.
In temperate zones, the corms of most species and hybrids should be lifted in autumn and stored over winter in a frost-free place, then replanted in spring. Some species from Europe and high altitudes in Africa, as well as the small 'Nanus' hybrids, are much hardier (to at least -15°F/-26°C) and can be left in the ground in regions with sufficiently dry winters. Plants are propagated either from small cormlets produced as offsets by the parent corms, or from seed; in either case, they take several years to get to flowering size.
A popular 'Nanus' cultivar is Atom.