Water irises

"We began growing water irises over 20 years ago and almost immediately came across a number of problems. First of all, what exactly is a water iris? Technically this epithet should only be used for plants exhibiting 'water marks'. These are very small black inclusion-like marks discernable on the leaves of some irises when held up to the light. However, they are not always easy to see.

It is probably easier, and perhaps obvious, to apply the name to those irises which naturally, in their native habitats, actually do grow happily permanently submerged in water, though they can often survive in really damp ground. But then there are irises that in their natural habitat can tolerate either frequent or occasional immersion but in reality like moist conditions only; too much water will eventually do them in! This has led to a great deal of confusion and thus disappointment to many gardeners.

Sadly many suppliers are either ignorant of this important difference or don't care. So they merrily distribute Iris sibirica and Iris ensata in particular as water irises, which they definitely are not. The proper water irises are Iris pseudacorus, I. versicolor, I. virginica and I. laevigata.




There are also some species rather infrequently met with, such as I. fulva, and there are also an increasing number of sometimes very lovely hybrids, often with I.ensata for instance. These latter need careful observation to determine whether or not they take after the water iris parent in habit.


Secondly, we found a distressingly large number of water irises were being distributed with the wrong names. Sometimes the new introductions were not in fact new; the 'introducer' had through ignorance given an apparently different plant or seedling a name when the original was still about. Sometimes, seeds from named cultivars are grown and all the progeny are named for the pod parent. While one sympathises with the commercial need to increase numbers to satisfy demand, this latter is unprofessional, bordering on the dishonest because only rarely will the buyer get the plant he thinks he is getting. Cultivars must be propagated by division - this cannot be too strongly emphasised.

Indeed, in this particular case it is the practice of growing seedlings and passing them off as something that they are not, that more than any other factor, is leading to the loss of a frighteningly large number of beautiful garden plants. Becoming more and more conscious of this we applied for our irises to be recognised as a National Collection, as it was clear that they desperately need conservation. Our collection was given this recognition last year.

We are not alone, of course, but incorrect propagation is becoming a reason for the major loss of wonderful plants and is something that, I am sure, more and more collection holders will be fighting against. I have no wish to be alarmist but the situation is becoming so grave that before long the NCCPG National Collections could probably become the only source of correctly named plant material.

The yellow flag (Iris pseudacorus) is the water iris most familiar to us. As the fleur de lys, it has the most romantic place in the history of water irises, as an escaping King of France successfully hid from his enemies amongst a clump of the plant. Our Collection contains, at the time of writing, 21 varieties and cultivars, two of which have been bred here. The range of variation in flower colour extends from the deep butter yellow of the species through a range of ever paler yellows to white.

There is a dwarf form as well as clones of giant ones, and there is one double which is more curious that beautiful. It looks more like a yellow dishcloth than anything else. Another double is interestingly 'hose-in-hose' in form.

The variegated yellow flag emerges in spring with primrose-coloured leaves which become increasingly green as the season progresses; its early colour makes it invaluable, particularly when grown with plants having bronze foliage. In general, this plant has been reasonably free from muddled naming, though the cultivar 'Bastardii' is frequently sold as 'Sulphur Queen', presumably because its proper name is thought to be too strong for the over-genteel modern world. One would perhaps not mind too much, but I frequently see plants under both names in garden centres, and innocent purchasers take one of each under the impression that they are getting two different plants.


There have been a number of interesting hybrids. The most famous one is 'Holden Clough' which appeared in the Lancashire nursery of that name. However, although it seems reasonably certain that I. pseudacorus is one parent, no-one knows or is sure what the other one was: the flower is very striking - yellow heavily netted with brown.

Crossing with Iris versicolor has produced 'Limbo' which is a graceful and tallish plant with white and blue flowers, as well as 'Regal Surprise' which is also of good stature and has lovely red violet flowers set off with white on top. Using Iris ensata has produced the enchanting 'Chance Beauty' which has large pale primrose flowers veined with pink and emphasised by a brilliant dark yellow signal. We think this is probably the same plant as one called 'Moonbeam'. A mystery hybrid is 'Roy Davidson' whose parentage is unknown, but has a flower similar to 'Holden Clough'.

Iris laevigata is the famous Japanese water iris, and this comes in shades of blue, purple, lilac and white, with double and bicolor flowers. The variegated one retains its silver white and green leaves throughout the season. Sadly plants from Japan are much subject to disease and their export is forbidden by the Japanese government. They rarely survive. As a result we don't have the enormous range that they do in Japan and have had to develop our own varieties. This makes it difficult to equate early introductions with their Japanese counterparts and thus some names will remain dubious, as they should retain their Japanese names of course.

The Collection comprises 21 cultivars of the species, three of which were bred at the nursery here. Nomenclature problems are mercifully slight. 'Dorothy' has been shown to be an invalid name and is probably the same plant as 'Weymouth Midnight' bred by Norman Bennet with a marvellous dark velvety double blue flower. The laevigatas have the largest flowers of all the water irises and mature clumps make a handsome and delightful display from late May through until the end of June.

Another problem occurs with the laevigatas. Precise descriptions of many cultivars are impossible, as they seem to be very variable in details like the colour of the styles, and depth of colour in the spotting on the falls.

Confusion can arise between these irises and Iris ensata, as both were known as Japanese iris when introduced in the early part of last century. For instance, a couple of years ago we acquired with some excitement some plants under the name of 'Plum Purple' and 'Reveille', but these proved to be ensata, a species which has among its many varieties the famous 'Rose Queen'. It is worth mentioning that this is frequently sold as a laevigata, and one wonders how many plants get drowned as a consequence.

Hybridization has been carried out successfully giving us such grand plants as 'Aquatic Alliance' which is a cross (from Reid in the USA) with I.versicolor and is a good misty blue, and the rather darker 'Omoide' produced by Akira Horinaka in Japan. This is a particularly poignant name because omoide means 'memories' and the plant was named by Akira in memory of his nursery which was destroyed in the earthquake in the 1990s. This was a tremendous loss to horticulture as the nursery contained one of the greatest collections of Iris laevigata in the world. Further splendid hybrids, as yet unnamed, have been produced by Greg Speichert in the U.S.A. and Tamberg in Germany.

Iris versicolor is the American water iris and whilst its flowers are smaller than those of I. laevigata they are produced in greater numbers. The species carries blooms of a pleasant mauvy blue and perhaps the best-known variety is 'Kermesina'; this has flowers of a deep claret with white signals. The Collection contains a total of 39 varieties of which 28 have been bred here at Rowden. The flower colour extends from blue to purple, claret to pink and an array of lavenders and mauves to almost pure white. In several, the clear white of the signal makes an extraordinarily striking contrast with a dark blue or purple fall colour, in others the falls are attractively veined with strong colouring. Strangely this species does not have any doubles or variegated forms - a pleasure to be discovered in the future? Nevertheless this plant has been much used in hybridization, some of the results having been mentioned above. In addition to those, there is the smallish range of irises known as ×robusta. These are either virginica × versicolor or the reverse and include such well-known favourites as 'Gerald Derby'. In general these tend to be taller than their versicolor parent.

The Iris virginica of America is a tall, variable and bluer flowered plant than the foregoing and the Collection contains five cultivars. Two of these, 'Pond Lilac Dream' and 'Pond Crown Point' were developed by Greg Speichert in the U.S.A. and both are worthy of a place in any pond, 'Lilac Dream' being a lovely colour. 'Purple Fan' is also worthy of mention because its leaves emerging in the spring are a particularly deep bronze in hue. Finally there is 'Dottle's Double', which has six small widely-spaced petals giving the flower a star-like appearance. It does not look like an iris at all.

This account of our Collection would not be complete without paying tribute to the tremendous help we have had from Mrs Jennifer Hewitt, both in gifts of plants and from her encyclopaedic store of experience and knowledge. Additionally the Collection would be impossible to manage if it were not for the meticulous work in recording, describing and propagating put in by my wife."

Photos: copyright John Carter
_{Article reproduced from Plant Heritage Volume 11 No.1 Spring 2003}