Following last week’s post showcasing the large wild iris (Dietes grandiflora), this post features the other two wild irises in our garden: the yellow wild iris or peacock flower (Dietes bicolor) and the less well-known forest wild iris – or simply forest iris – (Dietes butcheriana), which is also known as the broad-leaved dietes.
The yellow wild iris (Dietes bicolor)
In the wild the yellow wild iris occurs only in specific regions proximate to the Eastern Cape seaboard, usually near streams and in marshy areas. Despite these limitations in the wild, it does well in a variety of conditions as a garden plant, surprisingly tolerating drought even though its natural tendency is to be near water.
The lovely pale yellow flowers only last for about a day, but during spring and summer so many blooms are produced that flowers are usually present, prominent on long stems among the plant’s narrow and pointed leaves.
Clumps of yellow wild irises in flower can be seen on the edge of our garden near our pond. Behind them, growing on the margins of the plantation beyond, is a small patch of woodland trees and shrubs planted by the previous owner of our property.
The yellow wild iris is fast growing and although it can cope with poor soil, of course it does do better in well composted soil. Generally it is a hardy plant and in addition to its ability to survive drought it is also frost-resistant.
As I mentioned last week, there are only six species in the Dietes genus, five of which occur in eastern regions of southern Africa. But I need to correct the statement that all five are endemic to southern Africa – I have subsequently read that one of these five species, Dietes iridioides (the wood iris), also occurs in central Africa and in Ethiopia (see http://powo.science.kew.org/taxon/60453852-2).
And what of the sixth species? Most interestingly it occurs naturally only on one island, Lord Howe Island, which is in the Tasman Sea between Australia and New Zealand. The species is named Dietes robinsoniana, ordinarily known as the Lord Howe wedding lily (http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:436876-1).
It most likely shares a common origin with South African Dietes species, perhaps indicating a link to Gondwanaland (Wikipedia). To quote from the SANBI website: “The most primitive of the six [Dietes] species, according to molecular analysis, is D. bicolor followed by D. robinsoniana. This suggests that D. robinsoniana got to Lord Howe Island through dispersal from an African origin, although how this could have happened is at present unknown” (http://pza.sanbi.org/dietes-bicolor).
The Dietes species are classed in the large Iridaceae (iris) family, which includes about 82 genera and 1700 species worldwide. Over half of the species of Iridaceae occur in South Africa, in 38 genera (http://pza.sanbi.org/dietes-bicolor).
The lovely flowers of the yellow wild iris are prominent on their long stems. After flowering only for a day the flowers shrivel and gradually the seed capsules develop. As with the large wild iris (Dietes grandiflora), the plants seed readily. The clumps also increase in size quite fast, making the yellow wild iris a suitable plant for mass plantings and as a ground cover.
The leaves of the yellow wild iris (Dietes bicolor) are long, narrow and pointed.
By contrast the leaves of the forest wild iris (Dietes butcheriana) are broad, earning the plant its alternative common name: broad-leaved dietes.
The forest wild iris (Dietes butcheriana)
The flowers of the forest wild iris are relatively dainty, so its botanical name Dietes butcheriana seems to be somewhat at odds with its appearance. But rather than having associations with any kind of butchering, the plant is named for Harry James Butcher (1866–1950), “a merchant from Durban, who gardened with South African plants and discovered this species” (http://pza.sanbi.org/dietes-butcheriana).
However, the forest wild iris is indeed a forest plant, and it grows naturally in forests, on shady slopes and along forest margins in the mistbelt forest regions of KwaZulu-Natal and in coastal and inland forests in the Eastern Cape.
The flowers are very short-lived, lasting only a few hours. No wonder then that the flowers are self-fertile and unlike other Dietes species they don’t need pollinators in order to form seed capsules.
Although the flowers appear to be dainty the seed-capsules are quite the opposite being large and robust in appearance. The seed capsules do not split as they dry; the seeds are only dispersed when the seed capsule finally disintegrates after remaining on the plant for several months. The seeds are slow to germinate and germination may take as long as four years.
The relatively slow-growing forest wild iris is well-adapted to shade and is perfect for a shady garden in frost-free areas. It prefers fertile soil and responds well to watering. If in a shady place it can withstand a degree of dryness in summer.
We are fortunate have native wild irises that are both beautiful and hardy. Above is a close-up photo of a yellow wild iris (Dietes bicolor) whose flower forms the basis of the naturebackin logo.
Posted by Carol