Irises are tough, nearly carefree, but not all of them

Published 2:33 pm Friday, March 13, 2020

Most types of iris are tough plants, nearly carefree and that’s what I like about them. But the absolutely prettiest irises I have ever seen were Japanese iris growing in somebody else’s yard at Raymond. I bought a few and soon learned they didn’t fit in with my iris maintenance routine. They need TLC, a nearby water faucet and a gardener into hose-holding. So I’ve stuck with ones easy to dig and transplant and like to be mostly left alone.

Our most common iris types grow from rhizomes, which are below ground horizontal modified stems. And since iris plants do best with their rhizomes just below ground or even with the top sides exposed, they don’t need babying with mulching and such.

The rhizome irises are the ones referred to as bearded, non-bearded and crested. Bearded ones have a fuzzy patch in the center of each of the three downward-turned flower petals, i.e. falls.

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Crested irises have a fuzz-less ridge at the same area on the three lower falls. And irises with petals that have neither beards nor crests are simply called beardless. The most popular iris varieties fall into the bearded group. However, some people think all bearded iris varieties are in the German iris group but this is not so: most bearded irises are not German irises.

The beardless types include the Japanese iris, Louisiana iris and Siberian iris. Crested irises don’t include the more popular ones in southern gardens. Some miniature iris varieties are crested and some of these are actually native plants here east of the Mississippi River.   

There are a few iris types that reproduce by bulbs instead of rhizomes. Dutch iris has bulbs. They are not native to Holland but were created by Dutch horticulturists who hybridized irises from elsewhere. The other bulb iris type is the dwarf reticulata group that grows to six inches high or less. Both of the bulb types are later bloomers than the rhizome irises.

Most iris types are drought tolerant. They go fairly dormant by late summer and are content to rest in the heat. The exceptions are Japanese and Louisiana types. The Japanese ones want consistent, even soil moisture, but they don’t want to be overwatered: they can be drowned out. Louisiana irises will grow in shallow standing water but that is not necessary. They do fine in flowerbed soil as long as it doesn’t get too dry.

My own experience with Siberian iris is it is as tough as any of them but it is very slow to multiply. The half-handful of plants I was given 20 or so years ago is now up to two clumps about dinner plate diameter.

Beware of a possible misnomer passed along as yellow Louisiana iris. It’s a wild iris scientifically known as pseudacoris, a nuisance plant for sure. Somebody gave me some once. It tried to take over everywhere: the yard, the pasture, the roadside. I occasionally still see some locally, but it didn’t come from me. I killed mine totally dead.

Terry Rector writes for the Warren County Soil and Water Conservation District.