(1913) Spanish Irises by Dykes

Gardeners' Chronicle p.253, October 11, 1913

NOTES ON IRISES.

SPANISH IRISES.

It is astonishing that the majority of gardeners should be content to grow plants year after year in their gardens without wishing to know whence they come or how they have been evolved. Every gardener knows the so-called Spanish Irises, but who can produce specimens of the wild plants from which they have been bred? It is easy to say that they are the hybrid offspring of Iris xiphium, but can any English garden show us specimens of a form of I. xiphium which could conceivably have produced them? Investigations have so far only pointed to negative results, and it would be extremely interesting if this note led to the discovery that the plants for which -we are in search do after all exist in an English garden.

In order to narrow the field of investigation we may first deal with the suggestion that Spanish Irises are of hybrid origin. By this we should mean that they had been produced by crossing two species, not by breeding together the various colour forms of one species.

There are six known members of the Xiphium group of Irises, I. xiphium itself and I. xiphioides, I. tingitana, I. filifolia, I. juncea and I. Boissieri. Of these I. xiphioides stands by itself, and differs from the others in the shape of its segments, and by its capsule and seeds. None of its peculiarities ever appears among Spanish Irises, and it may, therefore, be excluded as a possible progenitor. Of the remaining species I. xiphium differs from the other four in the structure of the perianth tube. In I. xiphium the short, broad, funnel-shaped tube is set immediately on the ovary, but in the other four species there is between the ovary and this broad funnel a linear tube, which we may look upon either as its prolongation or as an elongated neck of the ovary.

In this connection it is interesting to remember that the same formations of perianth tube and ovary occur also in the Spuria group, whose members bear other striking resemblances to the xiphium species, e.g., in the shape of the segments of the flowers and in the arrangement of the lateral branches on the stem, which occur, though rarely, on strong-growing forms of I. xiphium. Thus, I. graminea may be compared with I. xiphium, for in each case the ovary expands abruptly into the broad, short tube, while I. spuria and I. Sintenisii both exhibit that tubular elongation of the ovary at its upper extremity which occurs in the majority of the xiphium species.

If Spanish Irises numbered among their ancestors any of the species tingitanaj Boissieri, filifolia or juncea, which are all characterised by this tubular elongation of the neck of the ovary, we should expect to find some traces of this character among them. Indeed, I am inclined to believe from the evidence of an undoubted cross between I. xiphium and I. tingitana which was raised by the late Sir Michael Faster, and which resembles I. tingitana in all respects, and has the additional advantage of being hardy and floriferous without special treatment, that the presence of this neck to the ovary is dominant ever its absence.

We are forced, therefore, to conclude that the Spanish Irises must have been evolved from I. xiphium, taking the name to cover also the yellow-flowered forms which were described under the name of I. lusitanica. But the difficulty then arises that I. xiphium in the wild state seems to flower much later than our Spanish Irises. It has been found in flower so late as August and September on the Sierras del Pinar and de Cazorla in Southern Spain, while even at sea level on the south coast of France it is in full flower on July 1. I have specimens in cultivation from the neighbourhood of Beziers in the Department of Herault. and others which resemble them in all respects from Portugal, and both were recently in flower here on July 15. At. the other extreme we have the above-mentioned hybrid of xiphium and tingitana, which flowers in April, and the hybrids of the pseudo-filifolia of trade catalogues, which flower in the middle of May, a full fortnight or more earlier than ordinary Spanish Irises. The origin of the false I. filifolia is a mystery, but its offspring are both too large and vigorous and too early flowering for it to be a parent of Spanish Irises. The only wild form of Xiphium that flowers here with the Spanish Irises comes from Algeria, and the flowers are of a shade of blue that I have not seen elsewhere. In other respects it much more closely resembles our idea of the wild parent of the Spanish Irises than any other form of I. xiphium. Does a similar form exist in Spain, or is this one more case in which one of the commonest plant names in our gardens bears little relation to truth and exactness.--- W. R. Dykes, Charterhouse, Goldaming

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-- BobPries - 2014-07-15