Family: Iridaceae (irises and their relatives) Genus: Iris (true irises) Subgenus: Limniris (the Beardless irises; 13 series) Series: Californicae (the Pacific Coast Native irises)

WHERE DID THEY COME FROM?

    Beautiful wild irises form part of the exceptionally rich spring and summer flora in Washington, Oregon and California. Where could they have come from? And how did they get there?

    Asia and Europe host almost all of the nearly 300 recognized wild iris species. Only a couple dozen, all members of the "beardless iris" group, somehow reached and still flourish in North America.

    Botanists classify the wild beardless irises into several "series". Those growing along the Pacific Coast are members of the series Californicae. Their nearest relatives may be among the Siberian irises (series Sibiricae) ranging today between Japan, China, the Himalayas, central Europe and France. The Pacific Coast Native irises and seven (or eight?) of the eleven Siberian iris species share the same count of 40 chromosomes.

    Ancestors of today's Pacific Coast irises, like those of the other seven native American iris groups, probably reached the New World across the Bering Strait at various times during the Ice Ages when lowered sea levels left a broad land bridge between the two continents. Under favorable conditions, they extended their ranges eastward to the Atlantic shores and south at least into northern Mexico.

    Glaciers periodically blanketed much of the northern hemisphere, making huge areas uninhabitable. Surviving iris populations must have spent thousands of years isolated in favorable places.

    When the frigid barriers retreated during the interglacials, some of the plants came once again into contact. But over time they had adapted and changed, and many retained their new distinctive appearance and choice of habitat. This story was repeated over and over again during successive Glacial / Interglacial cycles.

    The isolation must have lasted long enough for irises from different areas to look and act differently, but not enough for them to become mutually infertile. When the ice retreated and their ranges once again overlapped, many were still able to cross and form hybrids. This seems to be the condition for all the PCI species; they can even produce hybrids with some of the Siberian irises (although "Calsibe" hybrids are almost always infertile).

    Thomas and Christina Tamberg in Germany have had remarkable success growing Calsibe (diploid) and (tetraploid) hybrids of these two ancient relatives.

OTHER NEW WORLD NATIVE IRIS

    With three exceptions, the only wild irises in the western United States are all members of the Californicae series. The other beardless irises growing wild in North America are:

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