IRIDACEAE

Iridaceae is a family of plants in order Asparagales, taking its name from the irises, meaning rainbow, referring to its many colours. There are 66 accepted genera with a total of c. 2244 species worldwide (Christenhusz & Byng 2016). It includes a number of other well known cultivated plants, such as freesias, gladioli, and crocuses.

Members of this family are perennial plants, with a bulb, corm or rhizome. The plants grow erect and have leaves that are generally grass-like, with a sharp central fold. Some examples of members of this family are the blue flag and yellow flag.

Members of Iridaceae occur in a great variety of habitats. About the only place they do not grow is in the sea itself, although Gladiolus gueinzii occurs on the seashore just above the high tide mark within reach of the spray. Most species are adapted to seasonal climates that have a pronounced dry or cold period unfavorable for plant growth and during which the plants dormant. As a result, most species are deciduous. Evergreen species are restricted to subtropical forests or savannah, temperate grasslands, and perennially moist fynbos. A few species grow in marshes or along streams and some even grow only in the spray of seasonal waterfalls.

The above-ground parts (leaves and stems) of deciduous species die down when the bulb or corm enters dormancy. The plants thus survive periods that are unfavorable for growth by retreating underground. This is particularly useful in grasslands and fynbos, which are adapted to regular burning in the dry season. At this time the plants are dormant and their bulbs or corms are able to survive the heat of the fires underground. Veld fires clear the soil surface of competing vegetation, as well as fertilize it with ash. With the arrival of the first rains, the dormant corms are ready to burst into growth, sending up flowers and stems before they can be shaded out by other vegetation. Many grassland and fynbos irids flower best after fires and some fynbos species will only flower in the season after a fire.

The family has a very diverse pollination ecology. Most species are pollinated by various species of solitary bees but many are adapted to pollination by sunbirds. These species typically have red to orange, trumpet-like flowers that secrete large amounts of nectar. Other species are adapted to pollination by butterflies and moths, carrion flies and long-proboscid flies, and even monkey-beetles.

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