The range of versicolor and virginica overlaps in the upper half of
Michigan's lower peninsula, so below is the relevant key and text from
Voss' Michigan Flora. I especially like the exserted ovary character
as it's easy to see even in photos, and seems to work for all my
photos of wild irises in Michigan. I have no idea if the key will work
on more southern forms of virginica, but it's worth checking out.
Sean Zera
Zone 5b/6a
Ann Arbor, MI
-----------------------
Voss, E. G. 1972. Michigan Flora- Part I Gymnosperms and Monocots.
Cranbrook Institute of Science Bulletin 55 and University of Michigan
Herbarium, Ann Arbor.
Base of expanded portion of sepal with a bright yellow spot, finely
pubescent with hairs as long as the thickness of the sepal; outer
spathe bracts of uniform texture and color; seeds round to D-shaped,
irregularly (but shallowly) pitted... Iris virginica
Base of expanded portion of sepal at most with a greenish-yellow spot,
with papillae shorter than thickness of the sepal; outer spathe bracts
with the marigns generally darker and more shiny than the rest of the
dull surface; seeds D-shaped, with a ± regularly pebbled surface...
Iris versicolor
The cauline leaves of I. versicolor are shorter than the tops of the
inflorescence, while in I. virginica the cauline leaves frequently
overtop the flowers. The ovaries of I. versicolor (at anthesis) are
somewhat shorter (1-2 cm long), at least one of them exserted on the
pedicel beyond the tip of the spathe; while in I. virginica the
ovaries (before forming fruit) are 1.5-3 cm long and usually are not
exserted. The bases of plants of I. versicolor are more frequently
flushed with purple than are those of I. virginica, which are
generally brown. But all of these characters are variable, and several
must often be considered before identification can be made. A hybrid
between the two species has been described as I. xrobusta Anderson, on
the basis of two colonies studied near St. Ignace and at Engadine
[Mackinac County].
-----------------------
Quoting Laurie Frazer <lauriefr@localnet.com>:
>
> On May 20, 2008, at 12:36 PM, James Harrison PhD wrote:
>
>> Now would someone tell me an easy way to distinguish versacolor
>> from virginica? Or, are they so interbred in garden plantings that
>> there is a spectrum?
>
> I believe it was Bob Pries who told me that the seed pods on
> versicolor are 6-chambered, while those on virginica are 3-chambered.
>
> Laurie
>
>
> ---------------
> laurie@lfrazer.com
> Shadowood - http://lfrazer.com
> The Irises of Shadowood - http://lfrazer.com/iris/
> Wallplates With Panache - http://lfrazer.com/wallplates/
