There are several species of small beardless iris that are suitable for the woodland garden or for the rock garden if given a more moisture retentive soil and some protection from the hottest sun. One of the most rewarding of these irises is Iris verna, a native of the eastern United States in the Appalachian and Ozark Mountains. Iris verna is something of a loner in the genus iris. It is the sole member of the series vernae with no other closely related species. I. verna, the Vernal Iris, blooms as it's name would indicate, in early spring, March to April in the Seattle area.
I. verna is a small delicate looking plant that seems to stand up to rainy spring weather better than one would guess from it's general appearance. However slugs can do it in overnight so you must be diligent in it's protection from our favorite mollusks. The narrow grayish green leaves grow to about 3" to 4" the whole plant at bloom time being no more than 5" at a maximum. The flowers are a deep clear lavender blue with a distinct orange slash on each fall. It is generally listed as needing acid soil but I find that it seems to do better for me on a rich well drained soil closer to neutral.
I have grown it for many years. My first plant came from a U. of W. Arboretum sale. I do not have a date when I acquired it but it was over fifteen years ago. It grew and bloomed most years until I had to move it twice in one year when we were building our new home. It is often said that I. verna resents disturbance and I guess that clone had heard the rumor.
My second plant came from Lorena Reid shortly after the demise of the first. That had to be in 1986 or 1987. I still have that plant and it has been moved once. It blooms usually every year and is growing in well drained soil at the edge of my rock garden. The rock garden scree soil in this area has been amended with a lot of peat and humus. The third clone I acquired of I. verna was from WeDu Nursery a form called I. verna smalliana which I purchased in 1989. It was planted near the second and though neither has increased greatly they both bloom most years. I. verna smalliana does seem to be slightly more compact as it was supposed to be.
Two years ago I was given a start of I. verna alba which I planted across the path from the other two in a newly worked bed that had been heavily amended with a commercial compost that is near to neutral in PH. This small start quickly grew to a clump as large as either of the other two plants but has refused to bloom for me. All of these plants are in high shade between my rock garden and the woods. I hope for bloom from the white one this spring.
It seems that a very humus rich but well drained soil with a neutral to slightly acid PH is to the liking of I. verna. The most beautiful plants of I. verna I have ever seen were in the Chase Garden near Graham, Washington. There were several clumps each at least eighteen inches to two feet across. They were totally covered with blooms. They were growing in nearly full sun. Their companions were phlox and daphne indicating the need for a rich neutral to slightly acid soil.
If you have a chance to obtain I. verna give it a try. If it is happy it will reward you with one of the best spring shows you can imagine. I must admit it is not often offered but watch for it at places like the Arboretum sales and at specialty nurseries. Seed is usually offered in the seed exchanges.