Grasses of the Edmonton Region. Part 7

Originally published in the July 2022 issue of the WildFlower News

By Patsy Cotterill. Photos by author unless otherwise noted.

This article will be dedicated to some of the common non-native, weedy grasses that frequent our area, most of which flower in mid to late summer. For more information on these species and images, please consult the excellent online resources. One native weedy grass is mentioned.

Smooth brome, Bromus inermis

This tall perennial, strongly rhizomatous grass, produces flowering stems 50-130 cam tall, singly or a few together. The leaves are flat, 5-15 mm wide, and usually hairless, sometimes with a bluish-green tinge. Most have a characteristic crimping or shallow “M” marking somewhere on the blade. The branched panicle is large at 10-20 cm long, open and spreading at flowering time in July but denser and more erect afterwards. The spikelets are also large, 15-30 mm, greenish or purplish in colour, slender and pointed, with 8-10 florets. They provide a good opportunity to study grass floral anatomy using a hand lens. Within each spikelet the oneveined lower glume and three-veined upper glume subtend the florets in which the lemmas are 7-13 mm and hairless. In lacking an awn at the tip of the lemma, or occasionally having an awn only up to 3 mm long, smooth brome is unusual in the genus Bromus. (Fringed brome, B. ciliatus, is an example of a common local brome grass whose lemmas have a distinct awn.)

Native to Eurasia, smooth brome, most likely introduced as a forage grass, has found the prairie steppes and disturbed grasslands of North America greatly to its liking. It is the grass people are most likely to see once they step outside carefully managed gardens or specialized and intact native communities. It grows in pastures, fields, degraded prairies and other natural areas, immature aspen stands, roadsides, and disturbed ground generally. It is the bane of managers attempting to restore natural landscapes as it is an aggressive colonizer that can outcompete native species given any kind of disturbance, and forms dense clonal patches or infiltrates compact native plant communities by means of its rhizomes. Even natural disturbance favours it; it will colonize pocket gopher mounds where it is present, and often forms a lush fringe round ant mounds. It occurs all across North America except for the extreme southeastern U.S.

On the plus side, a number of insects feed on smooth brome, and birds and small mammals eat its seeds. Young shoots are eaten by both small and large mammalian herbivores, and it provides cover for wildlife. (Even so, I cannot bring myself to like it!) A similar, related, native species, Pumpelly’s brome, Bromus pumpellianus, formerly considered a variety of B. inermis, occurs in the mountains of Alberta. It is a hairier plant, with hairs on the stem joints and leaves; usually an auricle (appendage of the ligule) is present, along with a distinct awn on the lemma.

Smooth brome.

L: flowering at Watson Creek campground, Cadomin, 2010.07.29.

R: patch before flowering in Patricia Ravine, Edmonton; 2022.06.22

Quackgrass, couchgrass, Elymus repens

This non-native perennial grass has a lot in common with smooth brome. It is widely distributed across North America except the extreme southeast, and also spreads and forms patches by means of long rhizome, although it is usually not as dense or as extensive. Its flower cluster is quite different, however; it belongs to the group of grasses that have spiked inflorescences formed by stalkless spikelets on both sides of the flowering stem.

Flowering stems rise 50-100 cm; leaves are more concentrated towards the base of the plant, flat and 4-8 mm wide; and may vary from green to dark green to bluish green. The spikes are 5- 15 cm long, erect, and with one spikelet per node on alternate sides. The spikelets are about 10-15 mm long and somewhat overlapping, consisting of oblong, pointed, strongly veined glumes that may or may not be awned and 4-7 overlapping, flattened florets. Lemmas are hairless, of similar size (8-12 mm) and shape to the glumes, and similarly awned or unawned.

Quackgrass seems to prefer more continuously disturbed sites than smooth brome, and often invades gardens, horticultural beds or poorly maintained lawns. It provides good forage. It is easily distinguished from smooth brome when in flower; vegetatively, the leaves lack the crimping of smooth brome and are more likely to have auricles, tiny projections from the very short ligules. (In straw condition, smooth brome foliage takes on a characteristic appearance that, once known, is easily recognized.) Quackgrass is sometimes erroneously referred to as crabgrass (Digitaria). Although two species of Digitaria occur in Alberta, both non-native, I have never seen any this far north. Crabgrasses are warm-temperate grasses.

Quackgrass. L: flowering spike. Date and location unknown. C: patch at edge of front yard, Edmonton; 2022.06.24, R: rhizome on a herbarium specimen collected in waste ground, Lynn Lake, Manitoba; 1974.08.02.

Green foxtail, green bristlegrass, Setaria viridis

The foxtail genus, Setaria, belongs in a group of grasses that have two-flowered spikelets, of which only one floret in the spikelet is fertile, and has a hard lemma and palea. The whole spikelet falls off at maturity, including the glumes. The group includes the aforementioned Digitaria genus, as well as Echinochloa and Panicum. Representatives of the last two occur in Alberta, including the Central Parkland.

Green foxtail is a non-native, fibrous-rooted annual, often forming small tufts. Leaf blades are flat and about 4 mm wide; the ligules are hairy, with the hairs extending a short way down the edge of the leaf sheath. The panicles, 3-20 cm long, form bristly spikes of densely packed spikelets. These are oval-elliptic, slightly flattened on one side, about 2 mm long and pale green with darker green veins. The bristly appearance is due to 1-3 bristles, 5-10 mm long, located below each spikelet, which are green or occasionally purple. The lower glume is membranous, and short with three green veins; the upper glume about as long as the spikelet and with 5-6 veins. The lemmas and paleas of the sterile lower floret are membranous, but those of the upper fertile floret are hard and minutely ridged, becoming dark brown as the grain matures. The entire spikelet later drops off, leaving the bristles behind.

Green foxtail is a native of Eurasia although the genus as a whole is best represented in warm- temperate countries. It is widely distributed across North America. Locally, it appears to favour warm, well-drained, disturbed soils. For example, it has been a persistent weed at Fort Saskatchewan Prairie, although as an annual it is easily removed.

Green foxtail. L: Image courtesy of nexles.com R: Image from soilcropandmore.com.info

Some less common weedy grasses in our area include crested wheatgrass, barnyard grass and witchgrass:

Crested wheatgrass, Agropyron cristatum, is one of only two species in the wheatgrass (Agropyron) genus left in Alberta, former species having been transferred to other genera with taxonomic revision. Crested wheatgrass, a tufted perennial, native to Russia and Siberia, has been extensively planted as a soil binder and for reclamation. This small patch was growing by a bus shelter in Edmonton, probably originating in a seed mix used for reclamation after street work. (2022.06.24).

Large barnyard grass, cockspur grass, Echinochloa crus-gallii, is a native of Asia and a robust, tufted annual that prefers moist, disturbed sites. It belongs in the same broad group of grasses as green foxtail, and its branched inflorescence consists of spikes densely packed with spikelets that resemble those of green foxtail but the sterile lemmas are long-awned. Considered a bad weed elsewhere in the world, it is nevertheless used as a forage grass and in reclamation. Photo taken in Edmonton, 2010.08.24.

Witchgrass, common panicgrass, Panicum capillare, is in this same group. According to the Canadensys Vascan database, witchgrass’s occurrence in Alberta is dubious, but in the past I have found populations in the parking lots of the Edmonton Municipal Airport and Grant MacEwan college on 104 Avenue, since gone. I found a specimen at Fort Saskatchewan Prairie the other day. The broad leaves splayed out in a rosette may resemble those of an undeveloped quackgrass, but at flowering time there is no confusing either species. It is a species of disturbed ground, roadsides, waste ground and shores. As an annual native to North America but weedy, it thus differs from the other four species considered. The photo is of a specimen collected at Edmonton Municipal Airport on 1988.09.24.

References

Bromus inermis in Flora of North America, vol.24. p. 206 (online).

Canadensys Vascan.

Elymus repens in Flora of North America, vol. 24, p. 334 (online).

Setaria viridis in Flora of North America, Vol. 25, p. 554. (online).

Kershaw, Linda and Lorna Allen,2020. Vascular Flora of Alberta. An Illustrated Guide. Self- published. Kindle Direct Publishing.

Moss, E. H. 1983. Flora of Alberta. 2d ed. ed. by J.G. Packer. Toronto, University of Toronto Press.