A Study of Grasses: Getting Intimate with Smooth Brome

Field of Smooth Brome (Bromus interims) flowering, ON (photo by Nina Munteanu)

My relationship with wild grasses has been dodgy at best. We’re not friends. In fact, until very recently, I’ve kept my distance from them, avoiding any curiosity about their anatomy or how they functioned, certainly not to closely inspect grass flowers. Zero interest. They were anathema, after all… 

Since I was a child, I’ve had allergies to grasses when they were blooming. Like clockwork, every June, I would feel the onset of itchy eyes, ears and throat, sneezing, runny nose and postnasal drip (so embarrassing!) The symptoms would run well into the summer months until, miraculously, by the time it was time to go back to school, it was all over. We call it hay fever, even though there’s no fever associated with it. What I suffered every summer was a version of allergic rhinitis as a reaction to the pollen of various plants. In this case, grasses; so, the hay in hay fever is in fact quite appropriate. What happens is the immune system perceives pollen as a threat and releases excessive amounts of histamine to protect sensitive openings such as ears, nose and throat.

I just suffered through it all. Sometimes, I would try an anti-histamine, but generally they weren’t effective and I disliked their side effects. In university, during the field work in the Eastern Townships for my master of science degree in limnology, I had to walk daily through meadows of tall grasses and clouds of pollen to get to the streams I was studying. I must have used dozens and dozens of boxes of tissues. But I go my degree.  

Then, miraculously, since birthing my son, the hay fever dissipated and the flowering grass returned to my graces—and under my closeup lens.

Most of us don’t look at grasses for the beauty of flowers. When most of us think of a flower, we visualize the quintessential perianth, the brilliant show of petals and sepals. By contrast, grasses seem far from showy; they may even appear boring, without contrast, colour or even form. But it turns out that grasses do have perianths, however modest they are, and this reflects a modified function. And something of a source of excitement, I was to learn.  

Smooth brome spikelets showing male and female flowers, ON (photo by Nina Munteanu)

It was early June and I was walking the trail through the local thicket by the river, when I first noticed them: tiny yellow rods dangling off the brome grass spikes. Already handsome in their general stature—an erect panicle of spikelets that spread out like a Christmas tree—the grass spikes were now covered in bright yellow ‘Christmas lights’. On close inspection, the rods looked like two slim ladyfingers stuck together and dangled off a thin filament out of the grass floret: these were anthers carrying pollen! Once I noticed the anthers, I saw among them white feathery plumes poking out of the two separated sheaths or bracts (the palea and lemma)—the female stigmas! I was now fully engaged. Ignoring my possible allergies, I gathered a few spikelets and returned home to investigate more closely with my hand lens and to document with the close-up lens of my camera. I also did some research on this common but intriguing grass. 

Spikelets of Smooth Brome with pendulous anthers and feathery stigmas, ON (photo by Nina Munteanu)

I learned that the inflorescence of the smooth brome grass is a spreading panicle (raceme of wiry branches) which consists of branching spikelets that, in turn, have overlapping florets. Each floret has protective sheaths (the palea and lemma) that cover the floret’s reproductive organs and associated parts: the male stamen of anthers hanging on filaments, the female pistil of stigma, style and ovary. At the base of the ovary sit a pair of scales made up of spongy cells called lodicules. Thought to be the rudimentary remains of the perianth, the lodicule’s function is to swell with water when the flower is ready to reproduce. The swelling pushes apart the protective sheaths covering the flowering parts, allowing them to emerge and present themselves to the wind, which will help spread the pollen to its intended target—a stigma of a nearby grass. The process of pollen shedding is called anthesis

Close up of a spikelet’s florets with female stigmas and male anthers and filaments of stamens, ON (photo by Nina Munteanu)

Because pollination is primarily through wind (less so by insects or mammals) both anther and stigma need to be out there, in the wind. the anther dangles precariously like a kite, able to catch any directional wind to release its pollen; the stigma’s feathery net effectively captures wind-carried pollen from another plant in the oncoming breeze.

Of course, like most successful “weeds”, Bromus inermis has an additional trick up its veritable sheathy-sleevey: it guarantees both spread and continuation through its extensive rhizome network of horizontal underground stems, which produce clone colonies.

Bromus interims in flower in a forest edge in Ontario (photo by Nina Munteanu)

More About Bromus inermis

Smooth brome (Bromus inermis) is a herbaceous (non-woody) forage grass and, like all grasses, a monocot (its seeds contain only one cotyledon or seed leaf; its leaf blades have parallel venation). It is a Eurasian perennial leafy, sod-forming (due to massive root system), cool season grass introduced to North America, where it was used for habitat rehabilitation such as roadside plantings for erosion control and a forage source in agriculture. Smooth Brome is best suited to cooler climates and generally hardier than Tall Fescue or orchard grass. It prefers slightly acidic to slightly alkaline well-drained clay loam soils with high fertility. It resists drought and extremes in temperature but shows susceptibility to disease in areas of high humidity. 

In Ontario, smooth brome serves as an excellent hay and pasture grass and as a soil cinder along roadsides and eroded banks. It often persists after cultivation and may infest succeeding crops, gardens and lawns. Allied Seed notes that Bromus inermis“ is compatible with alfalfa and other adapted legumes. The grass is highly palatable and is high in protein content and relatively low in crude-fiber content.”

The grass thrives in disturbed habitats, including meadows and fallow fields, cleared areas along roads, and woodland edges, where it can spread through rhizomes into dense clone colonies that exclude native grass species. Typical of many invasives, Bromus inermis grows in sun and partial shade and tolerates various soils and moisture conditions.The grass grows usually to about waist height as a single stem (culm) with three to five hairless nodes, flat basal and stem leaves. Its inflorescence is a 10-20 cm long panicle with ascending branches that support 2-3 cm long spikelets (flowering heads). Each spikelet in turn contains several male and female reproductive parts or florets. 

An interesting diagnostic for Bromus inermis, which I ran across in an Ontario Government website, is that its blue-green leaves are frequently marked by a transverse wrinkle, a kind of ‘watermark,’ resembling a “W” a short distance below the tip. I checked out the Bromus on my path and indeed found the signature “W” on most of the leaves; only the mark was more of an “M” if you were looking at the leaf with tip right side up. 

Smooth brome stem and leaf showing “M” shaped ‘watermark’ indentation toward leaf tip (photo by Nina Munteanu)

During my field observations, I also noticed that the spikelets of the blooming Bromus inermis varied in colour from whitish green to purplish-red. A handsome, though somewhat pesky invasive. And certainly not boring!

The name Bromus comes from the Greek wordbromos, referring to oats, given that the flowering heads resemble oats. The species name, inermis, means ‘unarmed’ or ‘without prickles’, referring to the absence or reduced length of awns on the florets.

References:

Friends of the Wildflower Garden. “Grass Structures.” PDF: https://www.friendsofthewildflowergarden.org/pdfdocs/grassstructures.pdf

Hannaway, D.B. 1998. Forage Identification CD-ROM. Oregon State University http://forages.orst.edu/resources/media/idcdrom/default.html 

Chapman, C.P. 1998. The Biology of Grasses. CAB International, New York, NY. 

Hitchcock, A.S.1950. Manual of Grasses of the United States. United States Government Printing Office. Washington, D.C. 

Howard, Janet L. 1996. “Bromus inermis” In: “Fire Effects Information System.” 

U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 

Fire Sciences Laboratory (Producer). Online: 

https://www.fs.fed.us/database/feis/plants/graminoid/broine/all.html

Iowa State University. 2014. “Smooth and Downy Brome Identification and Control.” April 25, 2014. Online: https://www.extension.iastate.edu/turfgrass/blog/smooth-and-downy-brome-identification-and-control

MPG North. 2020. “Smooth Brome” Online: https://mpgnorth.com/field-guide/poaceae/smooth-brome

Langer R.H.M. and G. D. Hill 1991. Agricultural Plants. Cambridge University Press, Cambridge, England.

Ontario Ministry of Agriculture, Food and Rural Affairs. 2021. “Ontario Weeds: Smooth brome.” Excerpt from Publication 505, Ontario Weeds. February. Online: http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/smooth_brome.htm 

Reaume, Tom. 2011. “Smooth Brome Bromus inermis.” PDF. Nature Manitoba: http://www.naturemanitoba.ca/sites/default/files/SMOOTH%20BROME.pdf

Nina Munteanu is a Canadian ecologist / limnologist and novelist. She is co-editor of Europa SF and currently teaches writing courses at George Brown College and the University of Toronto. Visit www.ninamunteanu.ca for the latest on her books. Nina’s bilingual “La natura dell’acqua / The Way of Water” was published by Mincione Edizioni in Rome. Her non-fiction book “Water Is…” by Pixl Press(Vancouver) was selected by Margaret Atwood in the New York Times‘Year in Reading’ and was chosen as the 2017 Summer Read by Water Canada. Her novel “A Diary in the Age of Water” was released by Inanna Publications (Toronto) in June 2020.

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