Gladiolus is the largest genus in the Iridaceae family with 255 species. It has been studied by taxonomists and now includes Acidanthera, Homoglossum, Anomalesia, and Oenostachys along with species once included in Antholyza. The geographic range includes Africa, Madagascar, Europe, and the Middle East. Gladiolus has been a treasured flower in many areas of the world. Many of the fancy hybrids that are popular garden plants had their origins in some of the South African species. Telling apart the European species commonly grown is challenging for most of us, especially since seed exchanges use a multitude of different names for what is probably the same species. Angelo Porcelli has written a paper entitled Gladiolus of Southern Italy that helps distinguish between Gladiolus byzantinus (considered by some to be a synonymn of Gladiolus communis), Gladiolus communis, and Gladiolus italicus.
Gladiolus plants are subjected to Thrips, especially the ones that grow and bloom in warm weather.
The standard reference book for the South African Gladiolus species is probably Goldblatt & Manning's hefty Gladiolus in Southern Africa. Another great reference is Saunders' Field Guide to Gladioli of South Africa written by Rod Saunders and Rachel Saunders with Fiona Ross. It includes in-depth species descriptions and habitat photographs along with distribution maps and flowering months of all the species. Rod and Rachel managed to find all but one of the species in flower in South Africa over a number of years before their deaths. Another useful reference is Gladiolus in Tropical Africa.
Many of the winter-growing South African species have delicate-looking, multicolored flowers that bear little resemblance to the large, bold-colored summer-growing hybrids found in garden centers. But many of them are tough plants that can persist in the ground in a Mediterranean-climate garden, and a few species (particularly Gladiolus tristis) will spread themselves around the garden by seed. These spreaders probably shouldn't be grown next to wild land in Mediterranean climates.
The name derives from gladius a short sword in Roman times (as in gladiator), and this is the name Pliny (around the first century AD) used in reference to the shape of the leaves of the species he was familiar with. It is said gladiators who survived were showered with gladioli and there is a Dutch saying "death or gladioli" which harks back to this.
Growing from seeds is not difficult for species in this genus. It is said that South African species require temperature under 20 °C to germinate successfully but Bill Richardson found that temperature fluctuation from -2 °C (28 °F) to nearly 20 °C (68 °F) during the day does not have a huge effect on germination. Since there are summer and winter growing species, one must choose the right time for planting. Winter growing species should be planted in the fall. Summer growing species should be sown in the spring, and require a somewhat warm temperature to germinate well. Room temperature (25 °C/77 °F) works well. Sow the seeds in a well-drained mix and slightly cover them with the mix. The papery wings that surround the seeds do not need to be removed. After sowing, place the pots in a tray with water and allow the medium to soak thoroughly. Above watering can dislodge the seeds and cause them to float to the surface. The seeds are most viable when planted within 1 year, although they can remain viable for longer. Allow a dry summer dormancy for the winter growing species and a dry winter dormancy for the summer growing species. It is probably best to not transplant the seedlings until they have completed their second season of growth.
Information on named species can be found on the wiki pages below or by clicking on the name of the species in the table.
The alternative Gladiolus indices list the same species sorted by color or growth cycle.
Southern African Gladiolus a-b - Southern African Gladiolus ca - Southern African Gladiolus ce-e - Southern African Gladiolus f-h - Southern African Gladiolus i-me - Southern African Gladiolus mi-pa - Southern African Gladiolus pe-r - Southern African Gladiolus s-t - Southern African Gladiolus u-z - Gladiolus hybrids - Miscellaneous Gladiolus