An Iris resembling Iris aphylla

Many rhizomatous bearded irises are loosely called “Iris germanica” in Australia, and I have to admit I was guilty of this in the Flora of Australia (1984) and the Flora of South Australia (1986). Even the complex garden hybrids known as Tall Bearded Irises are sometimes lumped under this binomial, although the real Iris germanica L. is highly unlikely to have contributed to any of them, being difficult to use in a breeding program.

Among them are several distinctive cultivated clones; you may find them in your garden, or your neighbours’ gardens, or growing feral on waste ground from plantings several (human) generations ago. It seems approriate to call them clones as they represent a small number of quite uniform phenotypes with no intermediate forms, and rarely if ever produce seed. One of these irises that is frequent around Adelaide resembles I. aphylla L. at first glance, but can only be included in the broadest concept of this species.

It’s clear that the epithet “aphylla” used by Linnaeus in Sp. Pl. 38 (1753) did not mean that the plant is leafless at flowering time, although that may be the case in the colder parts of its historical range, which extends from the Balkans north to Germany and east to Russia. He actually wrote “scapo nudo longitudine foliorum” – with a naked scape the same length as the leaves – implying that he saw leaves and flowers together, as shown in the habit photo at Plants of the World Online. By “scapo nudo” he surely meant that the scape did not bear any leaves apart from the bracts.

Rhizomatous perennial herb to 70 cm high. Leaves in a basal fan of 5-12, ensiform, glaucous, to 37 mm wide, 50 cm long, apices acute and straight or gently incurved, present throughout the year. Scape elliptic in cross-section, to 50 cm tall, naked apart from a bract subtending each of the 0-2 short branches. Bracts slightly inflated, cymbiform, herbaceous but densely purple-streaked. Flowers solitary or paired within the bracts. Perianth tube to 3 cm long. Perianth lobes obovate, to 6 cm long, indigo to dark violet, the outer series (falls) patterned with a dark network on paler ground in the lower part, with a beard of white hairs, those near the haft yellow-tipped. Anthers 15 mm long, white, on 15 mm dark blue filaments. Style branches indigo, shading to almost white at base. Ovary fusiform, 6-angled, to 15 mm long. Fruit and seeds not seen. Flowers in August in Adelaide, long before I. germanica and the Tall Bearded Irises.

Thus it differs from I. aphylla sens. strict. in the leaves, which are seasonal, fewer, broader, and strongly falcate in that species (Dabrowska et al., 2019).

There are several irises in southern Europe close to I. aphylla and included in it by Service (1997) that have also been given names at species level. They may be of hybrid origin (Colosante & Mathew, 2008) but none of them matches the one described above.

Many of the supposed species in Iris Section Iris could be ancient garden hybrids that have been given binomials as if they were actual species that consist of wild populations. It’s a similar story in many horticultural genera such as Citrus, where our familiar oranges and lemons are ancient hybrids bred from less familiar Asian species. Long before the well-documented hybridisation of irises over the past two centuries (Darlington, 1973) there may have been earlier cycles of hybridization, selection, and the survival of some forms as feral populations that botanists in recent times have interpreted as species. My father used to say that history is a lot longer than most people think, and this is surely true of the history of plant domestication.

I. aphylla sens. strict. is a tetraploid with 4n = 48 chromosomes, while I. albicans Lange and I. germanica are reduced tetraploids with 44. All three behave as obligate outbreeders in cultivation; seed can only be produced by hand pollination with compatible pollen. When documented hybridisation began in the 19th century the first Tall Bearded Iris cultivars were diploids produced from I. variegata L. and I. pallida Lam. with 2n = 24, and the contemporary tetraploids and hexaploids are derived from them.

For comparison, here is a plant matching Iris germanica L. in morphology and pigmentation – although I haven’t seen its chromosomes.

-oOo-

References

Colasante, M. & Mathew, B. (2008). Species of natural hybrid origin and misinformation in the Irises: A reappraisal of the presence of I. aphylla L. in Italy. Plant Biosystems 142: 172-178.

Dabrowska, A., Smigala, M. Denisow, B. & Winiarczyk, K.(2019) Biology of flowering and insect visitors of Iris aphylla L. (Iridaceae). Turk. J. Bot. 43: 798-808.

Darlington, C.D. (1973) Chromosome Botany and the Origins of Cultivated Plants. 3rd edn (Allen & Unwin: London).

Service, N. (1997) Section Iris. In The Species Group of the British Iris Society A Guide to Species Irises. 17-56. (Cambridge University Press: Cambridge).

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