(1920) Dutch And Spanish Irises by Dykes
The Garden, p.570 November 20, 1920
DUTCH AND SPANISH IRISES.
I am sorry to have to question Mr. Jacob's statements (page 538), but I am afraid he is mistaken in saying that the Dutch Irises of the firm of Van Tubergen have " no hispanica blood " in them, and also, I think, in representing this as the opinion of the firm which raised them. The facts of the matter seem to be that the basis of the strain is really the early flowering, or preacox, form of Iris Xiphium, of which hispanica is only- a synonym. For some reason or other this early flowering form has long been known in commerce as filifolia. though it has nothing whatever to do with the real species of that name. If I may be pardoned a digression into dry botanical details, I should like to draw attention to the fact that the whole question is easily settled for anyone who will look carefully at the flowers themselves. He will then find that I. Xiphium is quite peculiar among the Irises akin to it by the fact that the segments of its flower spring almost immediately from the top of the ovary and are not separated from it by any linear tube. This tube is very apparent in all the other species, named', xiphioides, tingitana, filifolia, juncea and Boissieri. Lusitanica, of course, is only the yellow-flowered Portuguese form of I. Xiphium. The real filifolia is found on the top of the Rock of Gibraltar ; also, I believe, on the hills in the neighbourhood of Ropda to the north of Gibraltar, and in North Africa. It is a very distinct species with red purple flowers, and, as far as I know, has not entered in any way into the composition of Dutch Irises. The origin of the false filifolia is somewhat obscure, and it is probably only a cultivated form of Xiphium from the South of Spain. At any rate, its flowers are sold in the markets of Gibraltar, and it is very- different in size and brilliancy of colouring and, in fact, of its early flowering from the small grey blue form of I. Xiphium which are found high up on the mountains and which there flower at midsummer or later, as they do in this country. Some, indeed, are so late that specimens have been described under a new specific name as I. serotina, but their late-flowering habit is only due to the high altitude at which they grow. To make Dutch Irises, all that need be done is to cross the false filifolia, which is more properly known as Xiphium preacox, with pollen of any of the ordinary- Spanish Irises, or with lusitanica, which is only the yellow-flowered form of Xiphium. The result will be an early-flowering race with large flowers and no sign of any linear perianth tube. If, on the other hand, any form of Xiphium is crossed with any of the other species, the linear perianth tube is always present, and there is no doubt that in one or two of Van Tubergen's Dutch Irises, I. tingitana was one of the parents and shows its influence in the presence of a linear tube. To sum up then, Dutch Irises are for the most part derived from the early-flowering form of I. Xiphium, of which hispanica is merely a synonym. The few exceptions are hybrids between that species and I. tingitana, and there is no evidence that any other species has entered into their composition. Boissieri is bearded, and the hybrids of it that I raised were also bearded. Hybrids of the true filifolia and Xiphium are quite unlike the Dutch Irises, and juncea is so distinct in many ways that its influence must surely have been apparent if it had been used.
W. R. Dykes.
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