Buffelgrass invasion in the ABC (and why people should be worried)

Clusters of Cenchrus ciliaris (buffelgrass) with whitish flowerheads in Aruba

To say that the southern Caribbean islands of Aruba, Bonaire, and Curacao (which are fondly called the ABC islands) have a somewhat small number of grass species would be accurate, and these include quite a few invasive species that are also prevalent in many other Caribbean countries.

During my visit to these islands last week, one of the more prominent invasives was Chloris barbata (subfamily Chloridoideae), its digitate inflorescence a common sight in disturbed areas. This species was present not only in the most urban of areas, but it popped up even close to the beaches.

Chloris barbata in Bonaire's Te Amo beach

But a more ominous invasive in the ABC is Cenchrus ciliaris (of the subfamily Panicoideae, syn. Pennisetum ciliare, aka buffelgrass in the USA), which has been notorious for its ongoing threat to the iconic Saguaro in the southwest USA. This species crowds out native vegetation, and because it exists in dense clusters, it can create continuous fuel sources for fires. Such fires are deadly to the Saguaro and other desert plants, which have not evolved to live through it.

Cenchrus ciliaris near Mambo Beach in Curacao 

C. ciliariis is from Africa and parts of the Middle East and Asia, and it was brought to the USA as a source of cattle forage and erosion control. It can tolerate arid conditions, and is thus a good fit in the semi arid environments of the ABC islands.

During a bus excursion around Aruba, I saw large fields of what I took to be this species beyond the main urban areas. But even in the very midst of the few towns that dotted these islands, I found C. ciliaris hiding in plain sight.

Cenchrus ciliaris in middle of road in Curacao

In Curacao, rows of this grass lined the canals emptying into Mambo Beach, and I even found it in the middle of a street in front of the Maritime History Museum!

The presence and continued proliferation of this species in the islands should be worrisome to authorities and to the inhabitants. The history of C. ciliaris in the American Southwest has demonstrated its ability to overwhelm native habitats, and the recent huge fires in Hawaii that killed hundreds is a warning about what can happen if people are surrounded by fire-prone invasive grasses. The fact that buffelgrass has been recorded as burning up to 871 °C, and indirectly recorded to temperatures of 900 °C. (MacDnald et al, 2013), is testament to its potential threat to the environment and people.

Masses of flowering C. ciliaris in Aruba

Hopefully, the authorities in the island have been taking steps to address this before it has the potential to become a major problem.

Literature cited

McDonald, C.J., McPherson, G.R. Creating Hotter Fires in the Sonoran Desert: Buffelgrass Produces Copious Fuels and High Fire Temperatures. fire ecol 9, 26–39 (2013). https://doi.org/10.4996/fireecology.0902026

The Purple Sentinels of Mulholland Drive

Cenchrus setaceous in Mulholland Drive

Mulholland drive is a scenic and winding road through the canyons of Los Angeles that connects the Hollywood Hills to Malibu.  It overlooks the City of Angels, and has been the home site of many celebrities, including Madonna, Jack Nicholson, John Lennon, Roman Polanski, Marlon Brando, Demi Moore, and Bruce Willis. Mulholland Drive has also been made rather famous by the movie of the same name, which stars Naomi Watts and is directed by David Lynch.

I visited this famous area last month and drove around the many mysterious and narrow roads that ramified throughout the sheltered canyons. It was a fascinating trip, and one that I had never taken, even though I lived in Los Angeles in the 1990s. I had decided to visit here because of Clive Barker's novel Coldheart Canyon, which is about ghosts in a celebrity mansion that was hidden in one of the many beautiful canyons.

Crowds at Lake Hollywood Park, with the famous Hollywood sign in the background.

While driving through, I could not help but notice that purplish flowerheads decorated some of the canyon sides in very thick masses. I tagged it as Cenchrus setaceus (synonymous with the older name Pennisetum setaceum), which is commonly called fountain grass here in the USA. This species is from the subfamily Panicoideae, and has been heavily used as an ornamental because of its beautiful and abundant inflorescence. In fact, this species is one of the most commonly used ornamental grasses in Florida.

C. setaceus lines road, with hills and mansions in the background.

C. setaceus is a C4 bunchgrass that is not native to the USA, and hails instead from North Africa and Western Asia. It is particularly aggressive in warm, arid environments with full sun. Unfortunately, this makes Southern California an almost perfect place for it to grow, and it has escaped from cultivation and become invasive. It outcompetes other herbaceous native plants to decrease diversity and available habitats for wildlife, and also significantly increases the chances of fires in the area. To add insult to injury, the species is not good forage. 

C. setaceus with Washingtonia palm in background

All these negatives of course passed through my mind as I drove along Mulholland Drive and gazed at the passing masses of purple flowerheads. But I also had to acknowledge the beauty of the sight, one that tourists probably noticed as well. Perhaps they even think that the specimens along the road were planted deliberately to beautify the surroundings, an ironic twist to the current fate of this invasive grass, given that it was originally brought here as part of the horticultural trade.

C. setaceus pushing against native Opuntia (?) cacti

There are of course other invasive weedy grasses along that road, including the almost ubiquitous Avena fatua/Avena barbata, which dot the hillside, albeit in smaller numbers than in more natural settings. But fountainhead grass is surely the most noticeable, and the most attractive. So the next time you travel to Southern California and decide to visit the canyonlands of the City of Angels, keep an eye out for the Purple Sentinels of Mulholland Drive. 

PS. Coincidentally, it's been an interesting month that has just passed, one that was celebrated by and for the LGBTQ+ community. Its symbol, the Rainbow Flag, has a purple/violet band, which stands for spirit - for the courage, energy, and determination to stand up to bullying and oppression. This is something that is sadly needed in today's world, where it has become okay to persecute those who are "others". So here's to all the brave people who just want to be and show who they are. Be strong.

 The Rainbow Flag. By Guanaco and subsequent editors, from Wikipedia

 

Accidental Epiphytic Beauty

Cenchrus setaceus

In December 2020, I discovered a grass that was perched between two large branches of a tree.

This made me start thinking about why the Poaceae, even though it's the 4th or 5th most speciose plant family, did not really have real epiphytic species. I discussed this mystery in that old post, and came to the conclusion that it probably has to do with the fact that grasses are creatures of the light and wind. True epiphytes are pretty much all animal pollinated, and tend to occur in forested areas.

But "accidental" grass epiphytes do occur, and I came upon an instance of this again when strolling around a neighborhood and canvassing the many ornamental grasses that graced its grounds.

Cenchrus setaceus inflorescence (white stigma and yellow anthers)

Varieties of Cenchrus setaceus (subfamily Panicoideae) were in evidence everywhere. They have beautiful cylindrical flowerheads that are tinged with purple, and I was gazing at a group of the ornamental C4 grasses when I was astonished to find that two of the specimens were literally growing from the trunk of nearby palm trees! Not only that, but both had flowerheads rising from their tops, a testament to the tenacity of the individuals.

Flowering accidental epiphyte (red arrow points to base of grass)

I examined one of them (see image below), and found that the shoots of the grass emerged from what I think are balls of moss that had adhered to the trunk. The moss piece felt hard to the touch and crumbled slightly when I handled it. So it is possible that seeds from this species had landed on the moss, and had been able to grow to maturity in such an unusual location.

Rooted in moss (Cenchrus setaceus)

Although Florida is considered a humid area, it does have a dry season when rain does not occur for many days or even weeks on end. But the air must retain enough moisture that allows not only mosses to survive on the exposed palm trees, but other more complex plants as well, such as the ferns and Tillandsia "air plants" that decorate many of the tree limbs here. In addition, this is a suburban community, and I have a feeling the various underground sprinklers that dot the landscape contribute some water as well. Finally, this species has been known to become invasive, and thus might possess some rugged attributes that belie its graceful appearance and allow it to colonize inhospitable locations.

But whatever the reason for their growth and survival, the two C. setaceus specimens certainly prove that the Poaceae might not have many true epiphytes, but it's not because of lack of trying.  

A meeting of giants

Flowerhead of C, purpureus

I admit I am not your typical tourist. Sometimes I like to wander the streets of cities I visit, just looking at all the flora and fauna to be seen. This was the case when I visited Florida City in Florida, which is close to Everglades National Park and Key Largo.

I was walking along the sidewalk of a busy street in this smallish city (ok, it was Route 1, a state highway!), when I had to do a double take. Along a dead-end side street next to one of the many motels in that area was a long row of gigantic grasses! 

Long row of gigantic grasses

They were tightly packed and stretched in an unending row from the start of the street (SE 1st Ave) to its end near the motel back. The grasses rose to 4 meters in height or more, and above some were whitish flowerheads.

Schoolbus parked next to C. purpureus for scale. 

My first thought was that I stumbled on Arundo donax, but a quick inspection of the flowerhead nailed the species as Cenchrus purpureus (syn. Pennissetum purpureum), which has various common names such as Napier grass, elephant grass, and Uganda grass.

Young C. purpureus spreading across a recently fallow lot

The grass had spread from the row to infest a field of trees behind it. The land looked abandoned, but a quick look at Google Street View from previous years showed that it had once been carefully tended, with palms planted in neat rows. Now young Napier grass sprouted from all over the field, and I was thinking that without tending that the lot would soon be filled with it. I also encountered another large stand of Napier grass east of the motels, along with smaller clusters that must have been derived from the larger stands (see image below).

C. purpureus in yellow, N. reynaudiana in red.

Interestingly enough, I spotted other large grass stands in the distance in the empty lot, but a quick look showed that they were a different species!

I trudged into the lot and found out that the new grasses were Neyraudia reynaudiana (Burmareed), their gigantic forms topped by huge plumes of brownish flowerheads. They were scattered in small clusters, and the nearest group was about 30 meters away from the equally tall Napier grass.

Neyraudia reynaudiana

I wondered what would happen when the two species finally met in that empty lot. Would one species be dominant over the other, or would they coexist, the two groups forming a field of gigantic grasses with distinctly different flowerheads? Which grass would prevail in this clash of giants?

Another interesting thing is that I have seen both species all over Southern Florida, but they both become much rarer as one travels north. I have not seen Burmareed in Lake Okeechobee (though I have seen what I took to be Phragmites australis in the distance next to the lake), while Napier grass was quite abundant on the northern lake shore. However, once one gets closer to Orlando, the glimpses of giant grasses becomes rare to non-existent, and I have only seen one cluster of Napier grass in the Orlando area. The specimens were located in Shingle Creek Regional Park, and they seemed a bit unhealthy looking.

N. reynaudiana on the road to Everglades National Park

It is a change to the landscape that is quite evident, perhaps even to the eyes of laymen. The land of giant grasses transforms into a land filled with Andropogon sp. and Aristida sp., much smaller grass species that nevertheless dominate many areas in a way that even the giants might envy.

Spider lurking in a C. purpureus inflorescence

A row of Pennisetum!

 

Image: Courtesy of 刘伟

I am not especially enamored of Pennisetum, but no one can deny that the flowerheads of these grasses are usually very pretty, which makes it a favorite ornamental.

Here 刘伟 lines up quite a few samples for our delectation (from left to right):

Pennisetum macrourum, P. setaceum 'rubrum', P. setaceum ‘Rueppelii’, P. orientale 'Tall', P. alopecuroides 'Purple', P. alopecuroides ‘Viridescens’, P. alopecuroides 'Hamelin'

Looking at things in a different way: Pennisetum setaceum and Panicum virgatum spikelets

I wanted to show how beautiful grass flowers can be, so I took a few macro shots of the spikelets of the warm season grasses Pennisetum setaceum and Panicum virgatum. 

Panicum virgatum 

In the images you can clearly see the fuzzy looking stigma, as well as the yellow anthers in the case of the Pennisetum.

In the movie Dead Poets Society, Robin Williams tells his students that We must constantly look at things in a different way.

Pennisetum setaceum

So the next time someone tells you grasses don't have flowers or are too plain, just tell them that all they have to do is to look at the world (and grasses) in a different way, because beauty sometimes hides in surprising places.

Panicum virgatum