Thursday, August 31, 2023

Update on Cogon Grass Reversion in Colorado

The previous article to this is here:

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

We will be heading back to the east this weekend, but before we leave I spent some time surveying the community for any other reversions.

I found a total of 17 clusters of Imperata cylindrica, and 12 of them had putative reversions. This means that more than 70% of the plantings gave rise to wild type Cogon grass. I mapped all the clusters for use later.

Cogon grass fills a planting area. The "hole" in the middle of the mass is because of the presence of a large sculptured rock

I determined that there was a reversion event by checking whether there were flowerheads and/or the body form had changed to all-green, along with a concomitant increase in height and size. Out of the 12 reverted clusters, a couple had flowerheads, but still had the reddish leaves and smaller size, but most of the reversions were distinctly different in vegetative form than the ornamental.

A short-statured bush is being choked by the surrounding cogon

This reversion of an ornamental form to the dangerous wild type again highlights the problem of ornamentals that are still being sold (including in big box stores) to consumers, even though some of the species are illegal in certain states (and in the case of cogon grass, the species is considered a federal noxious weed).

Unfortunately, the ornamental variety with its red-tinged leaves are beautiful, and even the wild type can be attractive. This is because the blades are quite straight and seem to rise up directly from the ground, and when I showed my wife the imposing stands of reverted cogon grass, she mentioned that they looked nice.

But not only is cogon grass a menace to native species, but it is also prone to causing large fires, and is thus a potential danger to people and human habitation.

Samples have already been given to the state university, and once it has been positively identified, actions to clear the infestations should begin.

Thursday, August 24, 2023

Hybrid Prairie Lawns in Colorado

Turfgrass to the left, natural field to the right, in front of residential complex in Broomfield, CO. The field is actually closer to the complex, which is to the right.

One of the things that has most impressed me during my stay here in Colorado has been the way they have managed to integrate natural components into the suburban and even urban landscape.

The so-called Open Spaces is one aspect of this. but I also found smaller examples that were even more immediate and accessible to people.

Turfgrass to the left, natural field in front of residential complex to the right

In many places I've visited, including Broomfield and Boulder, landscapers have integrated traditional lawn and ornamentals with natural fields of grass and forbs around residential and commercial buildings. In the picture above for example, traditional turf grass that remain cropped close to the ground stands next to an open field. 

Turfgrass lawn backstopped by natural grass field, in front of residential building

These hybrid prairie lawns (HPL) are quite attractive, and the natural fields pull the eye away from the rather dull and relatively boring turfgrass. Unlike turfgrass lawn, the natural fields changes in appearance over the course of the season, with more green tints in the earlier parts of the year, before the golden light browns of summer and fall as the grasses senesce. Another big positive is the significant savings to the property owner, since the fields are not irrigated, and mowing of the fields is kept to a minimum.

As far as I can tell, the fields in HPLs are kept quite natural, with most of the grasses being the usual naturalized exotics such as Bromus inermis, mixed in with natives such as Panicum virgatum and Sorghastrum nutans.

Bromus inermis, which is normally a big part of fields here

I kept wondering whether the HPL concept would fly in some other states. This part of Colorado is lucky because the area is naturally high desert, where open savanna and pure grasslands are natural parts of the landscape.

In a place like New Jersey for example, which does not normally have lots of natural grasslands, any space left untended would soon become a big mess of brambles and forbs and weedy plants, which isn't as "attractive" as prairies. Energy and money would be needed to maintain a "cleaner" look, and this would probably discourage landscapers from exploring possibilities.

I did notice even here in Colorado that parts of some natural fields have a proliferation of weedy looking forbs in them, but on the whole, the system seems to maintain a nice equilibrium of small and medium tall grasses, with some forbs mixed in.

This plus the heavily maintained turfgrass next to it proves that such HPLs are a great alternative to the more boring landscapes with pure turfgrass. 

 Now, that's a "lawn" that I would love to have all year round.

Panicum virgatum, another species that forms part of the field

Thursday, August 17, 2023

Barley and Millet: Yes, Some Foods Do Grow like Weeds

Hordeum vulgare (Barley)

Barley is the 4th largest in terms of grain production, behind the other grass crops such as maize/corn, rice, and wheat. The species was domesticated around 10,000 years ago in the Eurasian region, and most barley is used for animal fodder, with the rest being used as food or for the making of fermented products such as beer. 

I was walking along one of the sidewalks here in Broomfield, CO, when I noticed quite a few attractive looking grasses along the sides of a building construction site. They weren't the usual Hordeum jubatum (commonly called foxtail barley here), which is pretty abundant in the area, and instead looked like some kinda short wheat (Triticum aestivum).

Spikelets of H. vulgare

Intrigued by the specimens, I started looking more into it. In terms of identification, I like trying to figure out the various wheat-like species only about a bit more than I like trying to make some sense of the different wheatgrass species. But after poring over identification guides and some apps, I finally decided that what I was looking at was the common barley.

Well-developed auricles of H. vulgare

Hordeum vulgare is an annual from the subfamily Pooideae, and the fact that this crop species also grows as a weed is a revelation to me. It's like coming upon a vast field of rice that grew naturally, without any help from the hand of people. Nevertheless, it turns out that this species, even though cultivated for millennia, does indeed have the capacity to still grow adventitiously along roadsides and other off-field areas.

The specimens seemed to be concentrated in that small block, as I have not really seen it elsewhere in the area, which is also intriguing. In fact, close to this cluster (the next block over) I found a second grass species that is also used as a food crop.

Panicum miliaceum (commonly called Proso Millet) is in the subfamily Panicoideae, and is just one of the many species that make up the group of food crops called "millet".

Panicum miliaceum (commonly called Proso Millet)

Proso millet was first domesticated around 8000 years ago in Northern China. There are some suggestions that this species, because of its ability to be harvested in as little as 45 days after planting, as well as its ability to produce crop in very little moisture, may have formed the bridge between hunter gatherer lifestyles and more sedentary agriculture. 

Panicum miliaceum

The domesticated crop has a tendency to revert to wild type, and the single specimen that I found was growing near a construction site, next to some landscape plantings on the sidewalk. It formed an arresting sight, with the heavy flowerheads drooping in thick bunches almost to the ground.

It is tempting to imagine how these food crops were first domesticated. Perhaps some hunter gatherers who had missed out on snagging a large prehistoric herbivore were dejectedly slouching back home, when they chanced upon fields of Panicum miliaceum, their tops overflowing with ripe grains. Or perhaps the discoverers of this new food crop were women who had been searching for edible berries and other vegetable goodies. Maybe people were getting tired of the vagaries of hunting and searching for food, and decided that planting food crops close to you might be a better idea. Or maybe a plant started as a weed infesting earlier crop plants, but was later seen to be another good food source and thus domesticated. This was what happened in the case of oats (Avena spp), which started as weeds in barley and wheat fields. The study of how agriculture started is endlessly fascinating, and one that I'll likely get into in a future post.

As an aside, the sight of food crops like these still growing wild reminds me that humanity's time here on earth is but a blip in the much larger time periods that some species inhabit. If ever our kind dies out, whether through disease or war or some unlikely event that we cannot fathom, it's likely that many of our "domesticated" plants will revert back to their wild ways, their brief tenure as indentured "servants" to the "raging apes" soon forgotten in the dim corridors of time.  

Tuesday, August 15, 2023

How Invasive Grasses Killed Hundreds of People in Hawaii During America's Deadliest Fire in a Century

Wildfire near Yosemite National Park, United States, in 2013. (Wikipedia, public domain)

Invasive grasses have long been known to create grass-fire cycles that allow these species to expand rapidly across the environment. In such a process, the grasses provide abundant tinder material for fires, whether started naturally via lightning or through artificial means. Generally, they are optimized for utilizing and promoting fires due to several factors:

(a) their creation of high fuel loads, which refers to how much fuel is present and available to burn. Grasses in general, and invasive grasses in particular can form very high density clusters.

(b) their low live to dead biomass. Annual invasive grasses in particular create vast fields of very dry dead matter after they flower and seed.  

(c) their high surface to volume ratios. Grasses generally have thin blades, which means they have a lot more surface area compared to their interior volume. Higher values are correlated to shorter fuel ignition times, and hence faster fire spread rates.

Add in the fact that grasses typically recover rapidly following fires, and the result is that fires kill off most of their potential competitors, and allow the grasses to expand their range and continue the cycle ad infinitum.

A prime example of such a cycle is one undergone by Taeniatherum caput-medusae (medusahead grass), which along with Bromus tectorum (cheatgrass) and others have devastated vast areas of sage habitats in the Great Basin.

Hawaii is no stranger to invasive grasses, most of which were deliberately introduced as potential forage or as ornamentals, but have since escaped into the wild and have outcompeted the natives in the islands. These include Megathyrsus maximus (called Guinea Grass in that area), Melinis minutiflora (called Molasses grass in some places), and Cenchrus setaceus (called fountain grass in some places).

Megathyrsus maximus spikelets (inset inflorescence), with purple stigmas and yellow-orange anthers

Last week, a massive fire destroyed the town of Lahaina in Maui and became the deadliest fire in the USA in a century. As of this writing, 99 people have been confirmed dead, but officials warn that the final tally could be double or triple that.

The initial cause of the fire is not known, but changes in the climate in Hawaii (including long-term declines in average annual rainfall and drought), coupled with the spread of invasive grasses to produce vast grasslands, are thought to be major factors in creating and maintaining the large wildfires after its initial start.

Escaped Cenchrus setaceus rows in Mulholland Dr, in Los Angeles, California

It's been a few years since I travelled to Hawaii, but I watched the popular TV series Lost a couple years back. This show was mostly shot in Hawaii, and it was interesting to see how many times I saw what seemed to be large expansive stands of Megathyrsus maximus, which is a large species and thus easier to see identify. The clusters were not only in savanna habitats, but also seemed to exist as smaller groups within forested areas.

I also remember visiting California this year, and seeing masses of escaped Cenchrus setaceaus along the roadsides in San Diego and even in Mulholland Drive in Los Angeles, where they doubtless increase the likelihood of spreading and exacerbating any incoming fire.

In the end, this major tragedy again highlights the importance of not only implementing measures to curb and address global climate change, but it should also focus people's attention on the importance of stopping the spread of invasive grasses. 

Perhaps most people may (sadly) not care about the destruction of sage brush habitats by such invasive grasses, but they surely will care about people's homes and lives being lost to the same types of invaders. A good start would be to enact legislation that will address this problem now, including banning or regulating the sale of invasive ornamentals and forage.

Wednesday, August 9, 2023

Here come the Four Horsemen of the Prairies

Panicum virgatum in Open Space area, in Broomfield, CO

Colorado is short grass territory (or at the least the eastern part of the state is), but as summer here is getting into full swing, I noticed that some of the iconic tallgrass prairie species are starting to show themselves.

The Four Horsemen of the Prairies refers to four species that tend to dominate the prairies farther east. The ensemble cast includes Andropogon gerardii (Big Bluestem), Panicum virgatum (Switchgrass) , Schizachyrium scoparium (Little Bluestem), and Sorghastrum nutans (Indiangrass).

Sorghastrum nutans in Broomfield, CO

I must admit that I was not really looking for them, engrossed as I was by the more western oriented species here, but I was walking along one of the Open Spaces in Broomfield when I spotted what looked to be Panicum virgatum in flower. The largish specimens lined part of the path, and a quick check of the flowerhead confirmed the identity.

I've always been a fan of this species as an ornamental, but seeing it in situ always is a treat, especially when in flower.

Sorghastrum nutans in Broomfield, CO

The second "horseman" I saw was one that for one reason or the other, I have not encountered much. This time, I found a slew of Sorghastrum nutans (Indiangrass) flowering along a sidewalk in Broomfield, CO, as well as in the various trails around Boulder.

Many people consider it a beauty, but personally, the fleshy colored and awned flowerheads of the species has never struck me as particularly attractive. Nevertheless, I was enchanted by the small flowerheads, which had escaped the mower blades by virtue of being shielded underneath some metal handhold along the path.

Schizachyrium scoparium along sidewalk in Broomfield, CO

And then there's Schizachyrium scoparium (Little bluestem), which I have owned as an ornamental and is an attractive plant to me. Unfortunately, the single specimen I have stumbled upon so far was still in the earlier stages of flowering, but I am looking forward to seeing more of this species going forward. 

Ladybug on Bothriochloa ischaemum(?). Where art thou Andropogon gerardii?

I was also on the lookout for the biggest horseman of all - Andropogon gerardii (Big Bluestem), but all the lookalikes I found at first seemed to be of some other species...specifically, Bothriochloa ischaemum, which is called yellow bluestem or King ranch Bluestem (in Texas).

Andropogon gerardii near Enchanted Mesa Trail, Boulder, CO

There are trails in that city called Lower and Upper Bluestem trails, and so I expected to find bluestems in the area, which I did. Unfortunately, most seemed to be yellow bluestem (Bothriochloa ischaemum) at this time.

It did not help that my identification skills aren't the best, but I finally found specimens of this large species during one of my hikes in Boulder. Not, as it turns out in the bluestem trails, but in trails closer to Chautauqua Park. Perhaps later in the season this tallest of the Four Horsemen will make its presence more widely known.

Sporobolus michauxianus (formerly Spartina pectinata) near Lower Bluestem Trail, Boulder, CO

Finally, I also found a really tall and attractive species that I identified as Sporobolus michauxianus (formerly Spartina pectinata). This is commonly called Prairie Cordgrass here, and it has amazing
pinkish anthers! When I first saw it from a distance I thought it was some weird A. gerardii, but I'm happy to have met the acquaintance of another spectacular looking member of the Poaceae during my trip to Colorado.

Sporobolus michauxianus (formerly Spartina pectinata) near Lower Bluestem Trail, Boulder, CO