Easy irises

Sunday, 04 September 2011

Iris wattii

Not all types of Iris are easy to grow in our warm temperate climate, and I broke my heart in my early gardening days over some of the exquisite ones I read about in English gardening books - such as the fruit-scented Iris graminea, blue Iris reticulata, the strange Iris foetidissima with its spectacular red seedpods and any number of other ones whose names now escape me. Most of them hailed from places like Spain and Turkey, with climates very different from ours, and their failure in my Sydney garden now makes eminent sense to me. But there is still something about Iris flowers that I find irresistible and I have sought over the years to find species that will grow well here.

White form of Iris japonica

Some of the easiest of all to cultivate in Sydney flower in late winter and/or early spring and are known as the crested (or Evansia) types of Iris - so-called because they have a 'crest' or ridge on their three larger outer petals (or 'falls') instead of a 'beard'. The majority of these crested types come from Japan and China, and in general, they grow very well here. Instead of wanting baking sun in summer and cold winters like the Mediterranean types, they are denizens of a semi-shaded woodland setting and are generally not as frost hardy as other Iris species. The most well-known form is Iris japonica, blooming now, with evergreen leaves formed into fans 45 cm in height, which multiply quickly into a thick clump via surface-rooting rhizomes. Pale blue or white ruffled flowers appear on branched spikes to 60 cm tall. Iris japonica will cope with quite dry, neglected conditions; however, they will do better if they are given some moisture (but not too much, as they may rot if drainage is poor), a yearly feed and a blanket of mulch every so often. They are said to dislike lime. They grow well under trees or shrubs such as Camellia japonica and Rondeletia and they are good companions to some of the smaller shade-loving flowers of late winter and early spring, such as hybrid hellebores, snowflakes, azaleas, Crassula multicava and bluebells. They look effective grown along the edges of paths in shady parts of the garden.

Iris wattii with Helleborus argutifolius in early spring

Iris wattii is a taller plant (ht 90 cm tall) with much bigger frilled flowers that are out now, coloured a lovely lavender blue and carried on bamboo-like canes that can be 1-2 m tall. They have the same growth form of leaf fans as Iris japonica, and make a good evergreen clump. They grow in the same conditions as Iris japonica and would probably grow well in a pot. I am enjoying one clump growing nearby a pale pink miniature Camellia and bright blue-spired Plectranthus barbatus; another clump has companions of the pale green saucer flowers of Helleborus argutifolius and the dainty lime-green bells of Nicotiana langsdorffii. Iris confusa is a similar tall Iris, with masses of near-white flowers; Iris japo-wattii is a cross between Iris confusa and Iris japonica, with flower stems up to 2 m in height and beautiful iced-lilac blooms. I haven't ever seen or grown these ones, however.

White form of Iris tectorum

Later this month, another crested Iris that does well in Sydney - Iris tectorum (ht 30 cm) - will flower. This comes from China and enjoys the same conditions as Iris japonica but will also grow in full sun. They have fans of ribbed leaves and pretty blue-lilac or white flowers; they multiply fairly quickly to form a clump. They do best if given plenty of fertiliser and water, but will still do well without them. The white form is said to be less vigorous, but I have found it to perform just as well as the blue. Iris tectorum is known colloquially as the roof iris because in Japan it is grown on the ridges of the roofs of thatched houses. Legend has it that this was because during a famine many years ago, only food crops could be grown in the ground so somewhere else had to be found to grow the Iris, the roots of which were made by the women into a face powder. Another theory is that the plants were so used because their roots helped to bind together the thatch and the wet clay used to construct the roofs.

Other crested irises include Iris gracilipes from China and Iris cristata, Iris lacustris and Iris tenuis from North America - they all prefer cooler climates to ours and do not flourish here like the other ones mentioned above.