(1912) Spanish and Dutch Irises by Dykes

Gardeners' Chronicle p.22, July 13, 1912

SPANISH AND DUTCH IRISES.

In an article on Iris filifolia, which appeared in the Gardeners' Chronicle for September 23, 1911 (p. 218), I mentioned the fact that it was not the true I. filifolia but another plant, which often appears under this name in catalogues and which might more appropriately be called I. xiphium preacox from its early-flowering habit, that was one of the parents of the hybrid " Dutch " Irises. I went on to say that the statement that all the known species of Spanish Irises were combined to produce these Dutch Irises was probably erroneous, for not one of them shows any trace of perianth tube, which would almost certainly have appeared sooner or later if either I. tingitana, I. Boissieri or I. juncea had been among the parents.

I am sorry that this statement should have seemed to question the accuracy of the raiser's account of the origin of these hybrids, and it would have been doubtless more correct if I had said that none of the hybrids that I had seen showed any trace of any other parent than I. xiphium and its varieties praecox and lusitanica.

Mr. C. G. Van Tubergen, of Haarlem, the raiser, has assured me that the pollen of both I. tingitana and other species was used to fertilise the pseudo-filifolia or xiphium prsecox. This statement I do not wish to traverse, but I am afraid I must still maintain that, except possibly in the shape of the blade of the falls and in the soft blue colouring of some magnificent flowers that Mr. Van Tubergen recently sent me, I have failed to find any trace of that structural difference which separates all the other species from I. xiphium. This difference is found in the perianth tube. In I. xiphium this is very short and funnel-shaped, and, as the flower withers, often breaks off from the top of the ovary with the withered remains of the segments. In all the other species, this short funnel-shaped upper end of the tube is separated from the ovary by a narrow, linear tube half an inch or more in length, which even when withered clings much more closely to the ovary.

None of the Dutch Irises that I have seen shows any trace of this linear perianth tube, and Mr. Van Tubergen admits that he has found no trace of it among his stock. This is the more curious because I had in flower this year a few plants of a cross of I xiphium x I. tingitana, which we owe to the skill of Sir Michael Foster. In this hybrid a linear tube of over half an inch is present, showing apparently that in the first generation of hybrids the presence of the linear tube is a dominant characteristic.

It had occurred to me that the seed parent might possibly have been I. tingitana, but Foster certainly called the hybrid I. xiphium X tingitana in a letter addressed to me not many weeks before his death. Another fact that tends to prove that I. xiphium was the seed parent is that the hybrid flowers freely every year and that the buds do not succumb to late spring frosts after the annoying fashion of those of I. tingitana, when the bulbs of the latter have at last been induced to flower.

This year both I. tingitana and I. xiphium x tingitana were growing here almost side by side and were in bud early in April. Then came the sharp frosts that played such havoc with the undeveloped flower shoots of I. germanica and caused large clumps of this species to remain apparently flowerless, though the frost-bitten immature flower stems could be dissected out of the bases of the tufts of leaves. These frosts killed the buds of I. tingitana entirely, but left those of the hybrid unharmed, so that they opened on April 15, which must surely be almost a record for a Spanish Iris flowering unprotected in the open.

The question of the date at which Spanish Irises flower is very curious. Only to-day (July 3) I have received from the south of France a few bulbs of what must probably be one of the last remaining colonies of I. xiphium that still survive in the wild state in France. These were found in flower on June 30, quite close to the Mediterranean on the coast of Herault, although it was supposed that the extension of the vineyards right down to the seashore along that coast had exterminated the colonies of I. xiphium tliat used to grow there. It might certainly have been expected that I. xiphium would have flowered a month or two earlier in such a warm locality, for with regard to other Irises the month of April there corresponds to June in the south of England.

The fact that the wild I. xiphium may flower so late, even in such a locality, tends, however, to show that it is unwise to separate from that species such Spanish plants as have been described under the names of I. serotina, Willkomm, and I. Taitii, Foster. Willkomm' s name of serotina was given to a plant which was found in flower in August and September. Herbarium specimens also show that I. xiphium can be obtained in flower in August and even in September at a height of over 5,000 feet on the Sierras de Cazorla and del Pinar in the south of Spain. I. Taitii has been in cultivation here for several years now and flowers at the end of June or early in July.

In spite, however, of the existence of these late-flowering forms of I. xiphium, I cannot admit that the early-flowering character of a hybrid is evidence that its parents were species other than I. xiphium. Several hybrids of I. xiphium praecox, crossed with pollen of I. lusitanica, which is only a yellow-flowered form of I. xiphium, certainly flower a week or two before either of their parents with the first of the Dutch Irises, with which they seem to be identical.

It is an interesting speculation to try to discover the nearest point of contact between bulbous and rhizomatous Irises. It seems not impossible that this may be found in I. xiphium and I. spuria. The form of the segments of the two flowers is identical, the spathes are not dissimilar, and when, as sometimes happens in strong-growing examples of I. xiphium praecox and of hybrids raised from it, a lateral flower develops on a short vertical branch, the resemblance to I. spuria is particularly striking.

That I am not alone in seeing the resemblance between I. xiphium and I. spuria is proved by the fact that some years ago I was informed that flowers of I. hyerensis were on their way to me from the south of France. Imagine my surprise when, on opening the box, I found a number of fine flowers of I. tingitana which had been picked and sent to me by mistake for I. hyerensis. The latter, by the way, is nothing but a cultivated form of I. spuria, in spite of its reputed origin from a cross between a Kaempferi hybrid and I. xiphioides ! It is probably only one more example of the process which is continually going on in any collection of Irises, and by which self-sown seedlings of such self-fertilized species as I. spuria, I. Pseudacorus, I. versicolor or I. setosa come up where other seeds have been sown and have failed to germinate or where other and rarer species have failed in the struggle for existence. --W. R. Dykes, Charterhouse, Godalming.

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-- BobPries - 2014-07-16