Cogon in Colorado: An Alarming Case of Natural Reversion from the Ornamental Variety

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The highly aggressive Imperata cylindrica is normally considered an invasive weed, but it is sold as an ornamental in some places due to an attractive variety called Japanese Blood Grass or Red Baron.

This variety has reddish leaves and is significantly smaller than the wildtype form. It is also notably less competitive than the latter. In addition, flowering in this variety is extremely rare, and it is cold tolerant. 

Ornamental form in New Jersey

The problem with the ornamental variety is that it has been shown to revert to the aggressive green form under certain environmental conditions, and so this variety cannot be sold, traded, or grown in certain states that have major cogon grass problems. The fear is that it might hybridize with the green form to form very aggressive, and cold tolerant, varieties that can become problematic even in cooler areas.

Cogon grass stand in Broomfield, CO. The dense mass has started to insinuate itself into the nearby shrubbery.

Natural conversion from the ornamental to the green form is probably very rare, and in the many years that I have known it in New Jersey, I never encountered such an event. However, I was walking along a street in Broomfield, CO, when I had to do a double take and take a closer look at a stand of grasses. Rising from the dense mass were flowerheads that looked similar to the distinctive inflorescence of I. cylindrica. 

Spent flowerhead

Most had already lost their spikelets, but a few still had the characteristic fluffy white seeds of the species sticking to them.

White hairy seeds of I. cylindrica from the reverted stand

There was no trace of red blades in the stand, and the grasses were up to more than 1 meter tall, which is significantly taller than I've ever seen the ornamental variety grow. All indications pointed to the fact that these were wild type cogon grass. In fact, the stand looked exactly like any cogon grass stand in Florida, the dense mass almost excluding all other plants from living in it.

Spent flowerhead with a few fluffy seedheads still attached

I surveyed the area and found at least two stands of reverted cogon grass in the vicinity. In the second stand, there was a mixture of both ornamental and green forms, with the green forms sprouting multiple flowerheads as well. In both stands, a few other plants managed to hold onto their spots, including Bromus inermis, which is normally one of the dominant naturalized exotics here in the Boulder area. Most will probably succumb to the much denser and more aggressive I. cylindrica over time.

Dense mass of reverted Cogon grass fills up all the available space. The brown flowerheads to one side are from a few Bromus inermis that have survived in their midst

Broomfield, CO is definitely not a subtropical or tropical location, so to say that I was surprised to find green-form cogon grass in the place would be an understatement. The ornamental variety of cogon grass seems to be used here though, probably because the assumption is that the cold and snow would keep it in "safe mode".

The reverted wild type form is significantly taller than the ornamental form, and is green in color.

However, the record heat prevalent in the southwest right now is probably increasing the average temperature in this area as well. Add in the wet winter and spring this year, and conditions might be optimal enough for the ornamental variety to revert. 

Ornamental form between Calamagrostis spp.

The origin of the cogon grass is likely ornamental forms that had been planted along the sidewalk. I found a couple of these sandwiched in between the usual Calamagrostis ornamentals. 

The question on whether these naturally-reverted forms will continue to survive is important. Will the cold and winter of Colorado convert these back to the ornamental form going forward, or will the warming climate allow it to flourish and start aggressively taking over swathes of the environment?

Time will tell.

Note: I have contacted the relevant authorities who can handle these clusters, so they will probably be extirpated going forward.

Unlikely pairing of Bromus japonicus and Imperata cylindrica "Japanese Blood Grass"

A Beautiful Bouteloua Bonanza

Bouteloua curtipendula (side oats grama)

Species from the genus Bouteloua (from the subfamily Chloridoideae) are one of the dominant plants of the shortgrass prairie.

These relatively small grasses include Bouteloua gracilis (blue grama grass), Bouteloua dactyloides (buffalo grass), and Bouteloua curtipendula (side oats grama)

The shortgrass prairie is an ecoregion that is semi-arid, with cool winters and warm summers. It occupies a slice of land in North America to the west of the more famous tall grass prairies, with a region of mixed grasses between them. As indicated by the name, the ecoregion is dominated by short-statured grasses such as Bouteloua spp.

Modified from wikipedia By User: TheshibbolethHowpper 

A lot of the attention on prairies in general are focused on the tallgrass species, such as Andropogon gerardii, Schizachyrium scoparium, Panicum virgatum, and the like, but as I travelled through the states with mixed and short grass prairies, I fell into serious liking (even loving!) for the short-statured grasses that are found in these expansive areas.

Both B. gracilis and B. dactyloides are really small grasses, but their reproductive structures are quite distinctive and in my eyes quite beautiful. The inflorescence of B. gracilis (blue grama grass) is small, but easily seen with the naked eye even from the height of a person, since they usually occur in masses. 

B. gracilis

The species is especially attractive when the bright green anthers start poking out from the spikelets, and I have seen this species used quite liberally as ornamentals here in Colorado, and elsewhere, such as western Kansas. I remember my first experience with this species was in New Mexico several years back. At the time, I had never seen such an odd looking inflorescence.

B.gracilis with green anthers and ant on top!

B. dactyloides (buffalo grass) is even more unusual when it comes to reproduction. It is one of the few grasses that are mostly dioecious, with some individuals having only female flowers, and some individuals having only male flowers. In addition, most grasses have perfect flowers, which contain both male and female reproductive parts in the same flower, but B. dactyloides flowers are mostly unisexual, either having male OR female parts. 

B.dactyloides 

The staminate (male) flowerheads are distinctive, with bright orangey anthers. Unlike B.gracilis, it is a bit harder to spot B. dactyloides by its flowerhead from a distance, but I've found that experience seeing the grass many times does help.

B.dactyloides male staminate flowerhead

The female pistillate structures of B. dactyloides are even more unusual. They are hidden beneath the leaves, the 3 to 5 spikelets protected by spikes. Each spikelet has only one floret, and once fertilized the entire spike structure falls to the ground.

B.dactyloides female pistillate flowerhead

The species has been used as turf grass, and I remember wanting to see whether I could use it in my lawn in New Jersey. The main problem with its use as a lawn is that it does tend to brown and go into hibernation as the cold approaches, which would be slightly problematic in a suburban environment used to green lawns all year round.

B. dactyloides staminate spikelet

Finally, perhaps the most beautiful species in the genus that I've seen so far is Bouteloua curtipendula (side oats grama).

This is a somewhat larger species than the two others, and its inflorescence is a long spike. The spikelets have iridescent violet and green hues interspersed with cream, and look like streamlined and aerodynamic hood ornaments on a race car.

Bouteloua curtipendulaa (pre-anthesis)

The appearance of orange anthers later simply adds to the alluring look of this species. I usually see specimens of this species as lone individuals, unlike B. gracilis and B. dactyloides, which are more rhizomatous and spread out.as clusters or colonies. 

Bouteloua curtipendulaa with orange anthers and white stigma

There are other species in the genus here in Colorado, such as Bouteloua hirsuta, which has a rachis that extends well past the spikelets, and I am hoping that I get to see and photograph these as well in the short time that I am here. But in the meantime, I spend time marveling at the various little beauties that I find as I hike the the hidden and not so hidden pathways in the area.

Bouteloua gracilis with green anthers

More Evidence of Potential Animal Pollination In some Grasses

Purple stigma on the upper left of the hoverfly, as it looks around for yellow anthers

In previous posts, the topic of animal pollination of grasses was discussed.

Life without Animal Pollinators: Why Grasses Embraced the Wind

Bee mimicking fly on flowers of Phalaris arundinacea cultivar

I was looking at what I thought to be a small specimen of Andropogon sp. here near Boulder, Colorado, when I noticed that many small insects were landing on the flowerhead and spending time perusing through the yellow anthers.

The insects that buzzed and crawled among the yellow anthers and purple stigma seemed to all be hoverflies, similar to those that I had seen frequenting the flowerheads of Phalaris arundinaea in New Jersey. 

Hoverfly eyes a good meal

As I noted in the previous posts, the insects seem to eat the pollen directly using its extended proboscis, and this could facilitate pollination when pollen sticks to it and transfers to a stigma during its visit to another flower.

Like all grasses, A. gerardii relies on wind pollination for the dispersal of its pollen, and the reason behind its lack of dependence on animals is discussed elsewhere. But it would not make sense to turn down the services of insects and other animals when they could enhance delivery, and this is perhaps what is happening in this case.

Interestingly enough, there have been reports of other insects such as bees also rummaging among grass flowerheads, but I have yet to see such cases.

The Case for Urban Open Spaces

Bouteloua dactyloides staminate spikelet (from another location)

One of the first things I noticed here in Colorado is the prevalence of land called "Open Spaces". These Open Spaces are preserved land that is not developed, although they may be adjacent to the usual parks and other recreational locations.

According to the department that manages these areas in the city of Boulder:

The open space lands teem with native plants and wildlife and are home to threatened and endangered species. They serve as a buffer between Boulder and nearby development. They sustain agriculture uses and add untold benefits to the natural environment - clean air, water, and earth. The lands shape the urban mosaic of the Boulder Valley and provide residents with passive recreation opportunities. Trails are used by walkers, hikers, bicyclists, horseback riders, dog walkers and other passive recreational uses.

I visited one of these Open Spaces in nearby Broomfield, which has kept their city beautiful by preserving large tracts of land. In the Open Space that I visited there, walking paths crisscrossed the place, and people were jogging, walking their dogs, and generally just enjoying nature. I did some botanizing one morning, and found many native grasses, although they were outnumbered by the usual naturalized exotics that have become ubiquitous wherever humanity has taken hold.

Part of an Open Space in Broomfield, CO

I spent  an enjoyable morning just walking the paths and looking at the critters, and managed to identify some of the major species during my botanizing. As always, I am always open to corrections of my identifications.

One of the most notable denizens of the area was Bromus inermis, which existed in large clusters and is commonly called Smooth Brome. You can identify it not only by the recognizable spikelets and habit, but by a W crimp in the middle of the leaves. This species is an introduced forage grass, but it has become somewhat invasive in many places.

Bromus inermis

The native Pascopyrum smithii (called Western Wheatgrass here) was also quite abundant. It is rhizomatous, and so exists in the area in large groupings.

Pascopyrum smithii

Close to it I also saw Thinopyrum obtusiflorum, which looks somewhat similar, but is significantly taller than its neighbor. This species is not native, but had been introduced from Eurasia. It has a few common names, such as tall wheatgrass, rush wheatgrass, and Eurasian quackgrass.

Thinopyrum obtusiflorum

Another naturalized Eurasian species was also quite abundant. Agropyron cristatum is called crested wheat grass, and the sight of its flowerheads en masse was quite attractive.

Agropyron cristatum

There were also stands of what I first took to be escaped cultivated plants. but which may instead be a native called Hordeum brachyantherum (meadow barley). These were one of the taller species in the community, dwarfing everything but some of the Thinopyrum obtusiflorum specimens.

Hordeum brachyantherum

The smaller species I found along the sides of the path, and included native grasses from the genus Bouteloua (which has become one of my fav genera, and which I'll explore more in a later article).

Bouteloua gracilis (called Blue Grama grass here) was in evidence along the margins, their distinctive flowerheads dangling bright green anthers. This species is one of the dominant inhabitants of the short grass prairies in Eastern Colorado.

Bouteloua gracilis

I also found some specimens of the equally diminutive Bouteloua dactyloides (called buffalo grass here), another dominant species of the short grass prairies that has been used as turf. More on this later, but it is one of the few dioecious grasses, with some individuals having only staminate flowers,  and others only pistillate flowers.

Bouteloua dactyloides (staminate spikelet)

Other species that I found included the natives Panicum capillare, Bouteloua curtipendula, and Hordeum jubatum, as well as a few clusters of the invasive Bromus tectorum. In a creek, I even found a lone cattail (Typha sp, not Poaceae) surrounded by the invasive Phalaris arundinacea (Reed Canary Grass).

Phalaris arundinacea surrounds a lone cattail (Typha sp)

The variety of species was fantastic, and I loved the time I spent botanizing. All in all, I have to say that I am fully and heavily in support of creating such Open Spaces. I would rather see natural areas like these preserved, than more gated communities, mini-malls, McMansions and parking lots. 

As noted above, some of the advantages include:

• They serve as home to threatened and endangered species.
• They serve as a buffer between a city and nearby development.
• They sustain agriculture uses and add untold benefits to the natural environment - clean air, water, and earth.
• The lands shape the urban mosaic and provide residents with passive recreation opportunities. Trails are used by walkers, hikers, bicyclists, horseback riders, dog walkers and other passive recreational uses.

In addition, I believe Open Spaces give an airy and open vibe to a city, provide habitats for a large variety of plants and animals, and serve as a shining example of how nature and people can coexist together.

Kudos to the city of Broomfield, Boulder, and all the other enlightened communities in Colorado that have the foresight and the perseverance to protect the natural beauty of the land!