Q: Late last month, I visited Birmingham Botanical Gardens (BBG) and saw a miniature iris in flower. It was blue-purple and was growing in a raised bed. I think I remember the label said it was from
A: The plant you saw is Iris unguicularis (EYE-ris un-GWIK-u-lar-is), commonly called Algerian iris. Like you, lots of visitors are surprised to see an iris flowering in the fall because they are accustomed to seeing irises bloom in the spring and early summer. For people only familiar with the common bearded iris, Iris ×germanica (ger-MAN-i-cuh), or the aggressive and often invasive yellow flag, Iris pseudacorus (soo-DACK-er-iss), this little gem is a real eye-opener – or a nose-opener if you got close enough to give it a sniff and catch its light but sweet fragrance.
Native to Algeria, hence the name, and spottily in North Africa, Greece, Turkey and other Mediterranean and Aegean islands, Algerian iris is found naturally in sunny, rocky habitats, in soils that are typically dry and alkaline in pH. Flowers for us often start as early as mid-November and continue serially (i.e., not all at once) until sometimes as late as late March. As I have observed, they seem to need a significant frost to re-set their internal clock and start their flowering cycle. Warm periods in late fall and winter after the initial cool-down will stimulate flower production. While the buds will withstand a frost, the flowers will not. In any case, each one only lasts a day. And since the flowers are nestled down in the mass of evergreen, strap-like leaves, they can be overlooked or simply missed.
Few plants of Mediterranean origin are well-suited for
To successfully grow Iris unguicularis here, your best chance is in a raised bed, as you saw here in the Ireland Iris Garden at BBG. Raising the bed elevation improves drainage, as does our soil mix. In these beds it contains, from highest percentage to lowest: expanded shale, an inert, non-compactable materially locally sold under the Perma-Till® brand; mason's sand; crushed limestone, to raise the pH; a little organic matter in the form of ground pine needles; and native topsoil for mineral content. This has seemed to work very well for growing a number of both
I have not seen Algerian iris in local nurseries or garden shops, but you should inquire; failing that, shop on-line. Iris unguicularis 'Pumila' (POOH-muh-luh, or var. pumila) is smaller in stature and the flowers are darker purple; there is also a white form, 'Alba' (AL-buh, or var. alba). Iris stylosa (STY-lo-suh) is an old name (or a synonym) for Iris unguicularis; culture is the same for all. Small (young) plants will require a little watering during establishment, and may not flower until the clumps upsize after a season or two. The evergreen leaves eventually brown; these can be cut off, or "combed out" by hand, pulling off the ones that release. This is about the only care they require, and that only for appearance. Unlike the typical bearded iris mentioned earlier, Iris unguicularis does not require frequent division for strong blooming, rather, the opposite is preferred as established clumps flower much more heavily. If you wish to increase your stock, the literature recommends dividing Algerian iris in early fall, before the flowering season begins.
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