Thursday, March 30, 2023

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.  

Tuesday, March 28, 2023

Mutual Assured Destruction: Revisiting an unlikely occupation

Flowering inflorescence of Imperata cylindrica, with orange anthers and purple stigmas

About a year ago, I wrote about how an invasive grass (Imperata cylindrica) started taking over an island in the parking lot of a building complex.

March 2022

A month or so after I posted that, the owner of the lot acted and when I next saw the lot in May, the entire island had been stripped of its vegetation and probably drenched in herbicides. They had pulled the trigger and given up on being able to selectively weed out the invasive, assuring the destruction of both the invasive grass and all the ornamental plants around it. Even so, I still saw a few blades of cogon grass poking out of the scene of destruction.

May 2022

I visited the area again last week, and the island was still bare, with even the two trees seemingly dead. The owners must have been repeatedly treating it in order to prevent any new regrowth of I. cylindrica. This repeated treatment and monitoring for a minimum of 2 years is a common practice when treating I. cylindrica infections, in order to ensure total eradication.

March 2023

I decided to revisit this old haunt because I had encountered another cluster of I. cylindrica that was weirdly similar to the situation in that parking island last year. In this new case, the invasive grass had grown on the mulched beds of two sidewalk Palm trees, and covered almost 20 m2 at the bases of the trees. 

I. cylindrica cluster around the bases of sidewalk Palm trees

I had spotted it even from a distance because some of the ramets in the cluster were flowering, even though they had been cut close to the ground. When I came near I noticed that the white flowerheads were covered in orange anthers and purple stigmas.

I'm very surprised the cluster had avoided being eliminated by the groundskeepers in the neighborhood, who are usually quite liberal with the use of herbicides to keep most of the area weed free. Perhaps the presence of the palm trees, which are also monocots and thus susceptible to the same types of chemicals as grasses, had so far dissuaded them from acting.

I'm also slightly surprised that the thick mulch (tree bark) around the tree bases have had very little effect in preventing the spread of the invasive. The tenacity of this species can be admirable, even as the authorities curse its weedy nature, and I'll be sure to revisit the cluster occasionally when I can to see how it fares.

A nearby field of flowering I. cylindrica

Friday, March 24, 2023

Poaceae on the App: Grass Pro SA

Summary: It's a fantastic mobile app that went far beyond my expectations, and would be a great help for anyone who wants to learn about grasses in the southern part of Africa.

My first experience with a mobile app for grasses was for the grasses of Montana, and I found it useful and quite portable, since I brought my phone everywhere.

So when I heard about a new app called Grass Pro SA that focused on South African grasses, I immediately downloaded it from the Google PlayStore for my Samsung Android smartphone, and was immediately appreciative of its quality.

The home screen has a rotating background of very nice images of various grass inflorescence, and displays all the main sections of the app.

The Grass List is simply a long list of all the species in the app (there were 324 species when I tested it, but I assume they add to it over time), with the capability to search for specific species by name. The subsections within it contain more detailed info on each species, including nice images, the distribution, and personal sightings. More about this features later below.

Grass List

The Sightings section allows the user to submit and sync sightings of species that they find to the common database. This is a great feature that is not in the more basic Montana app, and allows users to participate actively in the building of the database.

Help and About gives very detailed information about using the app, as well as credits to those people responsible for its creation.

The Settings section is interesting, because it allows you set the language options for the species and common names. It was cool to be able to see what the common name of Imperata cylindrica is in Afrikaans for example (Donsgras), although most of the African common names seem to be missing (I tried Zulu and Xhosa).

Settings Section

The Location Section is one of the best features of the app, and it is not available in the free evaluation version. In the main page you can select whether you want to see grasses in your current location (I assume the app uses the phone GPS), from a selected area in a map, or whether you want to see all grasses in South Africa.

Location Main Page
I decided to try out the Select from map subsection. As you can see from the image below I selected an area in the southwest corner of Namibia (by just tapping at it), and the app immediately noted that it has records of 20 grass species in that area.

Finding species in a specific map location

I then tapped the search icon next to the label "20 grasses", and it brought me to a page where I was able to filter the results by specifying particular traits (see image below). The app allowed filtering using 8 different methods, and this was something that was really amazing to me. 

Ability to filter results via 8 methods

Not only can you filter via the usual structural traits, but you can also filter using such unusual ways as ecological information (grazing value, plant succession stage. ecological grazing status, weeds), and even via common uses! (see image below).

Filtering via common uses

Just to show how the process works, I went the route of using the major physical attributes to identity a specimen.

In this case, I got the option of filtering the 20 species using such features as plant height, inflorescence, spikelet, and leaf blade width (see image below).

Filtering using major or main plant features

I decided to go with inflorescence, and tapping it took me to another subpage, where I was able to select from various types, such as unbranched, panicle, and digitate flower spikes (see image below).

Selecting type of inflorescence

A small icon ("i") next to each image allowed me to go to a help and information page that went into detail about the inflorescence types, which was really helpful.

Info page about inflorescence types

After selecting unbranched, rounded inflorescence, I was taken to a list of 3 grasses that met my criteria.

Since I knew the species Cenchrus ciliaris, I picked that, and I was taken to a species profile page (see image below). This page not only contained full descriptions of C.ciliaris, but it also had several nice photographs showing the habit and fine detail of the species. In addition, it also displayed the full distribution of the species in southern Africa.

I cannot emphasize enough how cool this little mobile app was. It went far beyond my expectations, and a lot of work and effort must have gone into creating it. I highly recommend it for anyone who would like to identify and learn about the Poaceae in the southern part of Africa, and I hope similar apps are created for other regions of the world. 

I think my only minor gripe is that a lot of the African languages did not seem to have common names for the species, but both Afrikaans and English common names were included. The app was also a bit confusing when I used Current Location to try to see species near me. Since I am located in the USA, I thought that it would note down zero grass species nearby, but it seemed to indicate the presence of all 324 species. 

The evaluation version is free, but to see all the species in the database (324 species when I tested it), and be able to use the Location feature, the cost is an annual subscription of around US $10 (including tax).

Tuesday, March 21, 2023

A Flowery Conundrum: Allergic Beauty

Purple pollen bearing anthers in T. dactyloides

 It's that time of the year again when the world conspires to make me as miserable as possible.

This year, the slow change in global climate has resulted in an even earlier start to the allergy season, and pundits note that this will also stretch the season, something that is bad news indeed to countless allergy sufferers like myself.

Nevertheless, I like taking long walks in the afternoon, and while i was strolling along the landscaped sidewalks of our suburban community, I noticed how the rows of ornamental Trypsacum dactyloides (with the common name Eastern Gamagrass)  had started flowering.

The colorful purple anthers of this species are borne on white filaments, and when I stood in front of masses of the columnar spike-like inflorescence, my allergy suddenly took a turn for the worse. I started sneezing, and my eyes started to water somewhat.

Masses of anthers and filaments in the stamens of T. dactylodes inflorescence

My reaction was not surprising, given that some of the inflorescence were positively groaning under the weight of tons of pollen-producing anthers. 

If you remember from previous posts, this species is monoecious, with imperfect (or unisexual) flowers. Monoecious means that there are both male and female flowers on the same individual plant, and unisexual flowers have only either male or female parts. Most grasses have perfect flowers, where both stamens and pistil are present in a flower. 

The stamen is composed of anthers and filaments and is the male part of the flower, and the pistils are the female part of the flower. The stigma is the outermost portion of the female pistil, and in this species it is feathery in appearance, and also an attractive purple color. The stigma is involved in capturing pollen from the air, and its feathery appearance probably aids in this function.

A spider hides near a spent stigma and some anthers

In Trypsacum dactyloides, the male flowers are located on the upper part of the inflorescence, while the female flowers are near the base. I noticed that in some plants, some of the inflorescence have matured anthers, while in the rest of their inflorescence, it is the stigma which is showing first. In other specimens, both anthers and stigma are present at the same time.

Stigma of T. dactyloides

T. dactyloides is native to the area, and I love how landscapers have used it extensively in both commercial and residential properties here in Central Florida. Its dark green leaves and fascinating floral structures make it a very attractive addition to the scenery. But the same colorful flowers that I enjoy so much might also be a major contributor to the misery I feel every time Spring rolls around. Such is the paradoxical nature of life!

Stigma of T. dactyloides