The laevigata section of irises embraces the well known Japanese or Kaempferi hybrids. These hybrids have all been obtained from the single species Kaempferi, one of the four true species which comprise the group. Although essentially water lovers, the laevigatas, in common with all other irises, and with the sole exception of pseudacorus, dislike a badly drained soil.
Much confusion has existed between laevigata and Kaempferi, since they were first known to the European botanists a century ago. This is due to the fact that both species come from the same districts. They are found in swampy places near Lake Baikal, and along the banks of the River Amur. Thence, they occur eastwards through Manchuria, Northern China, to Korea and Japan. I wish to make it clear that where I write of Kaempferi, the reference is to the species Kaempferi, the source from which the Japanese have obtained their marvellous, but, I fear, rather monstrous, hybrids. By what means they have succeeded in modifying the wild type, and obtaining those huge double freak flowers, is a mystery. From the fact that they have obtained a double form of laevigata as well, we are forced to conclude that it was not merely a natural chance freak which gave them their first break, but a carefully guarded horticultural secret. And no part of the world, and in no section of the genus, has nature evolved for herself this form of freak flower. The double laevigata and the double Kaempferi of the Japanese are the only double irises in existence. In passing, it is interesting to note that the Japanese have done the same by the chrysanthemum and the cherry. But nature receipts the interference of these Oriental hybridists, and if their double hybrids are allowed to naturalise and seed, in a few generations the seedlings will throw back to the type of the wild species. Though first discovered to the Occident in 1837, the true laevigata is still uncommon in English gardens, and it is almost unknown here. This is no doubt due to the fact that until fairly recently it was taken to be synonymous with Kaempferi. Laevigata is chiefly distinguished from Kaempferi by the characteristic, which earned for it the name laevigata, which means "smoothed". The tall, sword shaped leaves are quite smooth, differing therein from Kaempferi, which carries down each leaf a distinct ribbing, or ridged veining. The colour of laevigata is a deep, rich blue, of a shade not seen in any other Iris. The standards are upright, and the falls tongue like, long and drooping.
There is a garden form of the type under the name L. albopurpurea, having, as the name suggests, white and blue flowers. The standards and style arms are white, and the falls are white heavily mottled with blue. Strangely enough, this quasi-albino characteristic acts as a Mendellian recessive, and albopurpurea breeds quite true to colour. In recent years there has been on the market and Iris, which is called laevigata 'Rose Queen'. This is apparently a hybrid between laevigata and Kaempferi , as although the shape of the flower is like laevigata, the leaves posses the ridged veining of Kaempferi. The colour of Rose Queen is an even tone of Peach Blossom or rose pink. It is easily grown, and very effective when massed.
The cultivation of laevigata is quite simple. Like all the group, it dislikes lime, but can be grown successfully in any good garden soil, provided that it is not allowed to dry out during the summer months.
Kaempferi, as mentioned, comes from the same districts of Northern and Eastern Asia as does laevigata. It was first noted by a Western botanists as a species in 1858, but has been in cultivation in Japanese gardens for centuries. The shape of the flowers is somewhat similar to laevigata, but the standards are not so tall, and the falls are perhaps a little broader. The colour is a rich, deep purple, relieved on the half of the fall by a narrow stripe of Golden yellow. There is also a white form. Cultivation is the same as for laevigata, but the Japanese hybrids require more attention. These latter should be given plenty of manure, preferably well rotted garden compost or animal manure, which is best applied during winter when growth is inactive.
Pseudacorus, the English 'Water Flag' is botanically classed in the laevigata section. This act is surprising to the casual observer, but careful examination of the plants will discover many liberties with the species laevigata and Kaempferi. Pseudacorus, is too well known to come within the scope of this series of articles, but, I might mention in passing, that it is well worth the attention of any Gardener with plenty of "background" space, and it will grow anywhere, though it does best in a rich, moist soil. Its natural habitat is over the whole of Europe, North Africa, and Asia Minor. The flowers are bright yellow, varying considerably in colour, size, and height, as would be expected where distribution is over so wide an area.
There is an American representative of the section in versicolor (syn. Virginica). This is the American "Water Flag," and although quite different from Pseudacorus, it has much in common with that species. Versicolor grows wild from Hudson Bay in the North to the Gulf of Mexico in the South. The usual colour is a pale blue purple, though there is a natural red-purple form called kermesina. Both are very desirable waterside subjects, and at easy to grow. Culture is the same as for other members of the section - a damp, lime free soil, rich in humus.
Botanical affinities between the four species of the laevigata section suggests that inter-crossing should not be a difficult matter, but with the possible exception of Rose Queen, no hybrid is known. In inter-crossing it is necessary to de-antherise the seed bearer as soon as the flower opens, as the flowers of all the members of the section are so constructed that self fertilisation is naturally effected.
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Credit and copyright Iris Hunter.