Like a Marble, or an Eye

More small blue things from May. Between travel and rain I haven’t had the opportunity to go hunting in Maryland for several weeks now.

This annual is truly one of my favorites, and I make a point of hunting for it every year. Venus’ looking glass (Triodanis perfoliata) likes poor soils; look for it in open rocky or sandy places.



I have been having so much fun shooting with The Beast (70-200mm lens). Just look at the sparkle on those petals!




This is a species of Sisyrinchium, probably S. angustifolium though I can’t be sure. Blue-eyed grass is the common name, and indeed the leaves are grass-like. It’s in the iris family.


And speaking of irises, the ones I obsessed over last year are going strong. The ones along the canal are, anyway. The ones in the vernal pool are growing like crazy but I haven’t seen flowers on them yet.

I wish I had some new pictures of Baptisia australis to share, but honestly I haven’t even been out to shoot them. We’ve had tremendous amounts of (badly needed) rain in recent weeks, and I know that part of the river well enough to know that one stand is under water. Here’s what they looked like budding up in early May this year.

The other stand I’m sure is fine, but the channel I need to cross to get at them is flooded, too. Here’s a picture from last year.

Drawing the Line

With permission granted to collect just a few more samples, I went back to the iris sites and got two capsules. Each one appeared to be ripe. Took them home, opened them up, photographed them…

And damn if I still haven’t reached a conclusion.

According to the Flora of North America, Iris virginica has

Seeds in 2 rows per locule, pale brown, usually D-shaped, 5–8 mm, pitted, corky. 2n = 70, 72.

while Iris versicolor has

Seeds dark brown, D-shaped, 5–8 mm, shiny, thin, hard, regularly pebbled, not corky. 2n = 108.

How would you describe these seeds?

Once again I sought expert advice, this time from the Species Iris Group of North America and an iris-specific internet forum. One kind gentleman wrote to me:

Elizabeth Miller, please see the paper attached below. Iris virginica is 2N = 70 Iris versicolor is 2N = 108, it is an allopolyploid stable hybrid of Iris virginica and Iris setosa (2N = 38) which occurred post glaciation after the Laurentide Ice Sheet shifted a population (dramatically) from Western North America all the way across to the East, into the range of Iris virginica. Since you have a permit for collection, you may wish to contact your nearest university with a Hort program and see if they can do an analysis. In general from a phenotypic perspective Iris versicolor has short standards, which it inherits from Iris setosa, which has bristle like almost invisible standards. But Iris virginica phenotypes are variable and some occasionally have a shorter or rounder standard. So it is best, and most accurate, to go with a chromosome analysis:

[Parental Origin and Genome Evolution in the Allopolyploid Iris versicolor]

I was also pointed to the classic article “The Problem of Species in the Northern Blue Flags, Iris versicolor L. and Iris virginica L.”, by Edgar Anderson, originally published in Annals of the Missouri Botanical Garden [Vol. 15, #3, Sept. 1928].

The article was fascinating, and I’ve been struggling to come up with a way to briefly summarize it while doing justice to the detail. If you’re interested in such things, it’s worth getting a (free) jstor account.

After introductory remarks and descriptions of the species, the author presents a chart of “Comparative Morphology”, followed by some interesting observations:

Wherever either species was studied, the individual plants which went to make up a colony were found to vary strikingly among themselves. They varied in every conceivable characteristic, both vegetative and floral… The flowers varied in size and form, in color and color pattern, in number and arrangement, in texture…

…It is thus apparent at the outset that no biometric method of distinguishing the two species can be a simple matter.

That made me feel better about my own failed attempts. It also made me wonder if I wasn’t right in thinking that the lumpers should have won this round. But earlier in the paper, Anderson writes

It has been found that what commonly passes for Iris versicolor L. is made up of two species… the species are wholly distinct and crosses between them are partially sterile.

So I kept reading, only to discover that after detailed analysis of numerous specimens, Anderson discards mathematical models and comes up with a fascinating method of comparing specimens by creating ideographs based on groups of characteristics. After comparing ideographs, Anderson concludes

In marked contrast to the variation between individuals is the general resemblance between colonies of the same species.


Above all, when the ideographs are considered as a whole, the two species remain completely and absolutely distinct. In spite of a wide range of variation in separate characteristics, when the combination as a whole is studied it is found to be strikingly constant. Iris versicolor remains always and unmistakably Iris versicolor, and Iris virginica remains always and unmistakably Iris virginica. There is not the slightest tendency to one species to merge into the other.

So where does all this leave me? I can’t create the ideographs without access to a large number of specimens – quite possibly more than either stand of irises affords. Which leaves chromosome analysis.

And that’s where I draw the line. Even though a botanist friend has promised use of her microscope so I can do it the “old-school way”, should I be able to collect samples of root tissue.

A Beautiful, Useful Pest


yellow flag iris, pale yellow iris
Iris pseudacorus


In motor racing a yellow flag shown to competitors is a warning: there’s a potential hazard on or near the racing surface, something that could cause a serious problem.

“Yellow flag” is a good name, then, for this particular iris. Native to North Africa and Europe, it was introduced to the US and Canada in the early 1900s as a garden ornamental. As early as 1911, it was found in the wild in Newfoundland, and it took only a few decades to establish itself as a serious wetland pest, capable of outcompeting all other plants to form dense monocultural stands.

This is not merely an aesthetic problem for people like me who enjoy the beauty of native flora. Loss of floral diversity leads directly to the loss of faunal diversity, from insects to mammals. The ripple effects of a changing hydrology can be enormous:

The clonal nature of I. pseudacorus causes it to form dense stands and thick, submerged rhizome mats (Idaho Invasives 2007, Lui et al. 2010) that can prevent the germination and growth of native species (sedges, rushes, etc.) and eventually displace them entirely (Lui et al. 2010, MNDNR 2012, Noxious Weed Control Program 2009, ODA 2012). This vegetative growth can also trap sediment, raise local elevation of the ecosystem, and alter wetland hydrology (Noxious Weed Control Program 2009, Sarver et al. 2008). Populations of yellow iris create a positive feedback loop: once established, the roots trap sediment, which enables growth of new seedlings, which in turn trap more sediment (Jacobs et al. 2011). This increase in sedimentation also creates new habitat for shrubs and trees, thereby altering it to a drier ecosystem (Lui et al. 2010, Sarver et al. 2008). This alteration reduces the food supply and nesting habitat of many fish and waterfowl that depend on wetlands (Noxious Weed Control Program 2009, ODA 2012).*

Like many invasive species, yellow flag iris is highly adaptable to a variety of growing conditions. It prefers to grow in shallow water or wet soils, but once established it is surprisingly tolerant of lower moisture levels. It also tolerates low oxygen levels, high organics levels, and it will grow in a wide pH range, from highly acidic to slightly basic.

Despite all this bad news, if controlled yellow flag iris can be useful. It has been shown to significantly reduce levels of pathogens, including E. coli and Salmonella. It is known to be able to remove heavy metals from wastewater and has been used in sewage treatment systems in the Czech Republic and China.

It’s a stunningly showy plant, a perennial that stands up to five feet tall with dark green foliage and bright yellow blossoms. It’s now blooming in several parts of the recently de-watered parts of the C&O Canal near Carderock. Found in most of the US and Canada (except for 13 states and provinces), it’s reported as invasive in 12 states, including Maryland (where it’s been found in eight counties) and is listed as prohibited or noxious in six states.

Strangely despite the obvious problems it is still recommended by Missouri Botanical Garden because it’s easy to grow in problem (that is, wet) areas of the yard and has pretty flowers, but they also note “yellow flag should not be planted along streams or ponds or lakes where it can spread into natural waterways…”



USDA Natural Resources Conservation Service
Missouri Botanical Garden
Maryland Biodiversity Project
University of Florida, Institute of Food and Agricultural Services
*Great Lakes Aquatic Nonindigenous Species Information System