How invasive annual grasses like Taeniatherum caput-medusae (Medusahead grass) are conquering the West

I was walking along some side streets during a visit to Reno, NV in July 2019 when I came upon a field of dried golden-colored grass.

I knew that Bromus tectorum (cheatgrass) was present in nearby Lake Tahoe, but a quick examination of the grass showed that it was instead another (and perhaps more serious) invasive species.

Medusahead grass overruns an abandoned lot in Reno, NV

Taeniatherum caput-medusae (medusahead grass) is an exotic annual grass that is currently invading rangelands across the western USA. Its presence significantly reduces biodiversity and alters the ecosystem by degrading wildlife habitats. The species also has very high silica content and its barbed seedheads deter herbivores, which results in grazing capacity being reduced by up to 80% as palatable plants are eliminated from the area. Even other invasive grasses like B.tectorum have lost ground to this more aggressive species.

Estimates of the current range of T. caput-medusae is that it covers at least 2.2 million hectares in the western USA, and that it is spreading at a rate of 12% every year. Along with other invasive grasses like B. tectorum, it is causing widespread destruction of the iconic sagebrush ecosystem of that region, with the diverse assemblage of species being replaced by vast monocultures.

The spread of T. caput-medusae is mediated by a fascinating feedback process. Studies have shown that  it has a difficult time penetrating well-established stands of dominant perennial bunchgrasses, but when some external event results in the temporary clearing of these other grasses, then it can very quickly establish itself and quickly dominate the landscape.

Photo credit: Steve Dewey, Utah State University, Bugwood.org

Some of the features of this species that promotes its dominance in any local area include:

1. It is a prolific seed producer and can produce 10,000 seeds per square meter under ideal conditions. Its seeds can then remain viable for several years in the ground.

2. T. caput-medusae forms a very thick thatch layer on the ground. This layer is very high in silica, which prevents quick decomposition and smothers any potential competing plants. T. caput-medusae seedlings however have no problems growing in them.

3. The barbed awns and high silica content deters herbivores, who instead  concentrate on competing plants in the vicinity.

4. T. caput-medusae germinates in fall, and continues strengthening its root system over the winter such that by spring it can compete effectively against other plants that are just starting to grow.

Once T. caput-medusae has managed to gain a toehold (or a roothold in this case), there follows a devastating cycle that quickly results in this species dominating the area.

The thick thatch that it produces after its above ground structures senesce accumulates due to its slow biodegradation, and this not only prevents other plants from germinating, but it creates a  layer of fine fuels that sooner or later catches fire. The intense fire that develops kills off most of the vegetation without harming the seeds of T. caput-medusae that lie waiting in the soil, and after the fire subsides the vicious cycle begins anew.

Another year, another burst of Microstegium vimineum (Japanese stiltgrass)

A carpet of M.vimineum surrounds a dead tree trunk 

The last time I had seen the invasive grass Microstegium vimineum (Japanese stiltgrass), it had been Fall 2019, and the grasses had already turned golden in color.

Before today, I had not seen the species during late Spring, but when we hiked the Watching Reservation in Watchung, NJ this afternoon, the invasive grass was already starting to show itself in force.

M. vimineum carpet goes deep into the shaded canopy

Although each individual grass was still quite small and had only a few leaves, the ability of this species to dominate and overwhelm its environs is not in doubt. Carpets of the grass had already started forming along the sides of some parts of the trail, and some clumps had even formed deeper into the forest.

I even found a clump of large ferns facing what looked like an encroaching mass of the invaders!

Ferns surrounded by M. vimineum

Sadly, I know that by the time winter comes rolling in, that lone group of ferns will probably be drowning in a sea of Japanese stiltgrass.

Buying Panicum virgatum 'Northwind'

Upright almost iridescent leaves of Panicum 'Northwind'

I read about Panicum virgatum 'Northwind' from another blog, whose author is also an Orang Poa ("grassman") and quite in love with ornamental grasses. In particular, he had a fondness for the cultivar, and his enthusiasm for it pushed me to look for the grass whenever I dropped by some plant shop.

Today I finally found it and immediately bought one. There were only two specimens left, and there was interestingly enough no large label to tell what they were. Even so, the plants were standouts and immediately drew me to them. I selected the larger plant, which topped out at around half a meter tall.

The blades of this grass are very straight and upright, almost stiff even. They seemed to glow with some inner light, and when I got to the counter to buy it, two of the counter girls remarked upon how beautiful it was, with one even going so far as to ask about the name.

Once I got home I noticed that the setting sun's rays had illuminated the top half of the grass, while leaving the bottom half in low light. I was entranced by the sight, and took a pic before the sun had fully set.

I am really looking forward to how this grass will develop over the season, and into next!

Hordeum jubatum (foxtail barley grass) in Baanf National Park

In 2008, I visited Baanf National Park and Jasper National Park in Canada.

In addition to the absolutely beautiful scenery (I highly recommend the place to visit), the area had lots of interesting grasses for us Orang Poa (grass people).

One of the interesting grasses I saw was during a trip to Lake Louise, when I noticed a purplish flowered "weeds" hugging the sides of the main path around the lake.

Hugging the path

 I looked more closely and was delighted to see that the grass had really beautiful inflorescences coming out of its somewhat bedraggled blades.

Lots of seedheads

I later identified the species as Hordeum jubatum, which is called foxtail barley grass by the locals. It is an ornamental grass in some areas due to its feathery fox-like seedheads, but it can also be quite dangerous to pets and the like because the awned seeds can attach and burrow into sensitive areas of dogs like their noses and ears, so deeply sometimes that surgery is needed to remove them.

But a more interesting tidbit is that this same grass was mentioned in this area more than a hundred years ago, in a gardening journal:

A striking feature of the national park landscape is the squirrel or fox-tailed grass, Hordeum jubatum. Clumps of it are found almost anywhere, but sometimes it takes posession of considerable areas of level ground, and, waving in the win on a sunshiny morning, is one of the most beautiful pictures imaginable.

- Gardening, vol 6, 1898 (Sept 15, 1897 - Sept 1, 1898)

I found it fascinating that the same grass that interested me today also enchanted visitors to the park more than a century ago!

Rice Paddy Art

(c) Captain76 - Wikipedia

There are some grasses whose very existence is honored and celebrated.

Such is the case for rice (Oryza sativa), which is by far the most important human food crop in the world, and directly feeds several billion people.

This species is so important to some cultures that it shows up not only in their religion, but also in their arts.

I have always been fascinated by rice paddy art, which I learned about several years back, where people use different varieties of rice to create pictures that can be seen from the air due to the different colors of the rice plants as they mature.

Perhaps the most famous town that does this is the town of Inakadate in Japan, which started the annual event in the early 1990s as a way to attract tourists.

Here is a video of the town and its work:

Curious Critter #1

I saw this curious grass that seemed to want to climb up a wooden post during a trip I made to the Caribbean in 2019. The exact location I believe was near Mahogany Bay, in the island of Roatan, Honduras.

Looks almost like Pennisetum clandestinum (kikuyu grass), but I have no valid identification so far.

Kentucky bluegrass goes wild thanks to Covid-19 Lockdown

We had just hiked some of the trails at the Rutgers Ecological Preserve in Piscataway, NJ when I noticed a field of grasses had flowered close to one of the trailhead entrances.

Spikelets of Kentucky bluegrass

I moseyed on over and found flowering spikes on top of short stems clustered in masses across the entire front of the large red sign for the preserve.

Membranous collar-like ligule of Kentucky bluegrass

The Kentucky bluegrass (Poa pratensis) in the area had not been mowed recently, perhaps due to the current Covid-19 lockdown, and the grasses had grown  almost knee high and flowered!

Panicle of Kentucky bluegrass

Kentucky bluegrass has been frequently touted as the ideal lawn grass, and I believe this is the first time I had ever seen it flower, since obviously most lawns are mowed rather frequently and the species is kept short and vegetative.

Dark green linear leaves of Kentucky bluegrass

The grass can be identified by its long linear leaves, with boat-shaped tips, as well as a membranous collar-like ligule and loose panicles.

I took some pics of the rather unusual sight, knowing that I would not get to see this again soon in the neatly-manicured lawns of my suburban community.

Phalaris arundinacea as an Ornamental Grass

Phalaris arundinacea (or Reed Canary Grass as it's known here locally) is a perennial C3 grass that has become invasive in certain wetland areas, where it forms dense monotypic stands as it spreads using its thick rhizomes.

The species has become important for various commercial uses. For example, its ability to grow in contaminated soil has made it a prime candidate for phytoremediation, and as a very fast grower it has also been used in biomass production.

The genus has also become infamous because of its ability to poison animals. P. arundinacea contains tryptamine alkaloids, and may also accumulate high levels of selenium. It has a history of poisoning cattle and sheep, and a related species was involved in the "drunken" behavior of kangaroos in Australia, which can end in the death of the animal.

The wild form of this species is green and very tall, reaching more than 2 meters high. But there are also several ornamental varieties which have become popular in the trade.

I bought P. arundinacea 'Strawberries and Cream' last Fall and planted it in an enclosed cement container. The grass thrived, and this Spring I had to transplant out some of the plants or it would have engulfed the Calamagrostis acutiflora (Karl Foerster?) that shared the enclosure with it.

I love the leaves of this grass, which are strikingly white and green, with some pinkish highlights. The species also seems pretty tough, and a few days after transplanting them out, the somewhat withered looking grasses had pushed out new culms.

New stems poking out soon after transplant

I expect they will soon spread quickly to fill the available space, hopefully before the heat of summer, as this is a cool season grass.

I love working with tough species!

A very rare flowering of Japanese Blood Grass (Imperata cylindrica)

I was watering some grass seedlings yesterday when I happened to glance at a stand of Japanese Blood Grass (aka Cogongrass) that I had planted by the side of my home, and the brief look made me do a double take.

The leaves of this ornamental grass are gorgeous, but this time something else caught my eye. Poking out from the red-tinged leaves were inflorescence spikes of an arresting purple color!

Purple two-lobed anthers crowd on the spike surface.

I talked earlier about how Japanese Blood Grass is simply a smaller form of the invasive Cogongrass, and about how it is not  a real threat in certain areas because it is slower growing and sterile. It also almost never flowers, and the fact that some of my own specimens had actually produced these beautiful purple spikes filled me with amazement.

There were a total of three (3) spikes protruding out of the massed leaves, at different stages of development. Each spike was around 9-10 cm in height, with a profusion of stamens and some pistils on its surface.

The filaments of each stamen was pure white, and at the end of each was a two-lobed anther that was an arresting purple color. Filamentous purple pistils could also be seen among the masses of stamens.

A less mature spike hides among the dense foliage.

One of the spikes was more mature, with the stamens and pistils fully extended out from the surface, but the two others were still developing.

Purple pistils are on the left side of the spike above, looking like fuzzy caterpillars.

However, the spikes seem to develop quickly. We had a very cold spell during the night (all the way down to 2 degrees Celsius), and by the next day (today) the more mature spike had seemingly dried up and become brown, while the two other spikes had almost fully matured.

One of the fast-developing spikes today.

I took macro shot of all the spikes, which was not easy given how short JBG grows. But I knew that I had better make the most of this fantastic opportunity, because who knows when the grass would flower again? 

The second fast-developing spike today.

Spring comes to Cheesequake State Park's Phragmites australis

I know that P. australis is an aggressive invasive that has displaced native plants and spread unchecked throughout the country.

But this grass still forms impressive stands, and their dried inflorescence look quite enchanting to most casual observers.

Dense stands of P. australis look bi-colored due to new green growth at lower end. New growth also in right foreground.

We hiked Cheesequake State Park in New Jersey, and it was interesting to see the new growth of this species rising out of the tall light brown remnants of the grass from last year.

The new growth was dwarfed by the much taller dried grass, but its vibrant green coloration made it stand out anyways. In fact, when looking at a monoculture of P. australis from the side, the difference in color made it seem as if the grass was bi-colored, with a green lower half and a light brown top!

P. australis is abundant in the park

The park itself was very well-maintained, with well-marked paths and even long wooden boardwalks that allowed you to traverse the boggy low-lying ground that occupied parts of the park.

P. australis grows abundantly in the lower and marshy areas, and forms dense impenetrable stands along the sides of paths and around some of the park lakes and ponds. It is however absent from the higher areas of the park, as well as directly below the shaded tree canopy.

I can only surmise that eradicating the invasive grass from the park would have cost too much, though it might be a small consolation to park managers that visitors probably found the dense stands of grass an impressive sight.

New green growth rises under the shadow of last year's dried remnants

The two faces of Imperata cylindrica (Japanese Blood Grass or Cogon Grass)

The red form of Imperata cylindrica (usually called Japanese Blood Grass here in the USA) is my favorite ornamental.

But what some people might not know is that this species has a dark side too. It also exists as a wild, non-ornamental form that is considered one of the top 10 invasive plants in the world, Cogongrass.

Wild cogongrass (c) Keisotyo from Wikipedia

The wild form of I. cylindrica is much larger and much more robust than the ornamental variety, and it does not have any red tinge to the leaves. It spreads rapidly through its very tough and sharp rhizomes, forming dense monotypic stands that displace and exclude other plants, which in turn negatively affects all the animals that depend on those plants.

The ornamental form is smaller, mostly sterile, and is much slower growing than the wild form. It also has attractive red leaves that make it a prized specimen among ornamental grass aficionados.

Unfortunately, under certain conditions, this ornamental form can revert back to the wild form or produce seeds, and so Japanese Blood Grass cannot be sold, traded, or grown in quite a few states.

Comparison of greenhouse grown Imperata cylindrica var. koenigii (Japanese blood grass), Reverted I. cylindrica var. koenigii (JBG Revert) and I. cylindrica (Wild-type cogongrass). (c) Cseke, L. J., Talley, S. M. A

I have grown the ornamental form for years now, and it is definitely a somewhat slow grower, and pure stands of the grass can be invaded and overwhelmed by other plants. Growers of this species should try to plant it in dense groupings from the beginning, then weed out any other plants that try to get into such stands. They should also be aware that this is not a bunch grass, but that it forms underground rhizomes that will pop out blades of grass distant from the main grouping.

If you are in a growing zone where there is no chance of the ornamental form reverting to the wild state, then this species can be a striking addition to your collection or garden.

How I mistook a bamboo grove for trees

I've been walking along a stretch of road to a nearby gym for nearly a decade now, and I sometimes noticed a lot of birds hiding inside the foliage of what I took at the time to be a stand of tight packed trees in the backyard of a nearby house.

The birds would always be noisy, their tweets mingling with the rustling of the leaves.

It was only yesterday that I found out the "trees" were really tightly-spaced bamboo culms, and the discovery made me flabbergasted. I only realized they were bamboo because I had walked on the other side of the road, closest to the tall fencing that separated the house from the road.

The culms were beautiful, their bright yellow colors broken by streaks of green.

I identified the species as Phylostachys aureosulcata 'Spectabilis', which has mostly yellow stems with green coloring on their sulcus.

This has only been the second grove of bamboos that I've seen in New Jersey (with the first being at the Rutgers Gardens), and its discovery perhaps is telling me to always looks closely at the world around me. I just might find something really cool.

Miscanthus sinensis cultivars - inflorescence and spikelets

The Frelinghuysen Arboretum  in Morristown,  New Jersey has a nice collection of various species and cultivars of Miscanthus, and I spent one afternoon in September last year taking some macro shots of the grass inflorescence and spikelets.

I was really surprised at the diversity of forms of this outstanding ornamental grass.

Enjoy!

Miscanthis sinensis 'Goliath'

Miscanthus sinensis 'Graziella'

Miscanthus sinensis 'Little Kitten'

Miscanthus sinensis 'Purpurascens'

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