Gramineae (Poaceae) - grass family
 

WeedsPoisonous PlantsHay Fever
Gerald A. Mulligan
Research Scientist and Research Institute Director (retired) and presently Honorary Research Associate, Agriculture and Agri-Food Canada,
Ottawa, Ontario K1A 0C6, Canada

Awarded the Lawson Medal by the Canadian Botanical Association in 2006
Read his biography "The Real Weed Man" available in print and ebook.
Click here to go to Weed Photos for this family

Most grasses have inconspicuous flowers that produce wind-blown pollen that can cause hay fever in some people

Avena fatua L., wild oats, folle avione
Annual, spreading by seeds; flowering stems 2 to 4 feet (6 to 12 dm.) high; throughout, but most common in the grain fields of the mid-west; grain fields, roadsides, and waste places; introduced from Europe and Asia. A troublesome weed in grain fields.

Bromus inermis Leyss., smooth brome, brome inerme
Perennial, with creeping rootstocks; flowering stems 2 to 4 feet (6 to 12 dm.) high; common in the mid-west, occasional elsewhere; roadsides, and waste places; introduced from Europe as a hay and pasture crop.

Bromus tectorum L., downy brome, brome des toits
Annual or winter annual, reproducing by seeds; flowering stems usually less than 2 feet (6 dm.) high; throughout, but most common in the drier areas of the mid-west and west; overgrazed rangeland, abandoned farmland, around farm and ranch buildings, railway beds, roadsides, and waste places; introduced from Europe.

Digitaria ischaemum (Schreb.) Muhl., smooth crab grass, digitaire astringente
Annual, reproducing by seeds; usually semi-prostrate; flowering stems 3 to 18 inches (8 to 45 cm.) long; throughout, but most common from southern Quebec and Ontario, southward into the United States; lawns, gardens, roadsides, pastures, and waste places; introduced from Europe. A troublesome weed in lawns.

Digitaria sanguinalis (L.) Scop., large crab grass, digitaire sanguine
Annual, reproducing by seeds; flowering stems 20 to 40 inches (5 to 10 dm.) long; throughout, but most common in southern Ontario and Quebec and southward into the United States; row crops, vegetable and flower gardens, roadsides and waste places; introduced from Europe. Does not seem able to compete with sod-forming grasses.

Echinochloa crusgalli (L.) P.Beauv., barnyard grass, échinochloa pied-de-coq
Annual, reproducing by seeds; stems 1 to 4 feet (3 to 12 dm.) long; eastern half of our area; cultivated fields, gardens, barnyards, ditches, riverbanks, roadsides, and waste places; introduced from Europe.

Elytrigia repens (L.) Desv. ex B.D.Jacks. [ =Agropyron repens (L.) P.Beauv.], quack grass, chiendent commun
Perennial, spreading by seeds and vigorous underground rootstocks; flowering stems 1 to 4 feet (3 to 12 dm.) high; a common and persistent weed throughout; grasslands, cultivated fields, gardens, roadsides, and waste places; introduced from Europe.

Hordeum jubatum L., foxtail barley, orge queue-d’écureuil
Perennial, spreading by seeds; flowering stems 1 to 2 feet (3 to 6 dm.) high; throughout, but less common east of the Great Lakes; meadows, lawns, ocean shores, dry saline depressions, roadsides, and waste places; native to North America. A very common fringe plant along roadsides in some areas.

Lolium persicum Boiss. & Hohen. ex Boiss., Persian darnel, ivraie de Perse
Annual, spreading by seeds; stems 6 to 18 inches (15 to 45 cm.) high; mainly weedy in fields of commercial grasses being grown for seed purposes in the mid-west; introduced from Asia.

Panicum capillare L., witch grass, panic capillaire
Annual, spreading by seeds; stems 3 inches to 3 feet (8 cm. to 9 dm.) high; throughout, but most troublesome in southern Quebec and Ontario, and southward into the United States; shores of rivers and lakes, cultivated fields, gardens, roadsides, and waste places; native to North America.

Phalaris arundinaceae L.- reed canary grass, alpiste roseau
A highly variable perennial grass that grows to 2 meters (6.5 feet) high. It spreads both by seeds and by creeping underground rhizomes. In North America it is made up of both native and introduced populations. There is apparently no reliable way of differentiating between native and introduced plants. Reed canary grass occurs in floodplains, riverside meadows, and other wetlands throughout Canada and all except the extreme southeastern portion of the United States. It typically occurs in soils that are saturated or nearly saturated during most of the growing season. However, it does not grow in soils where standing water persists for an extended period of time. Its ability to grow in very poor soils has resulted in its use on contaminated industrial sites. It has been utilized as a forage species, as a soil stabilizer, and as a component of lowland hay. However, some consider reed canary grass a major threat to wetland ecosystems. It often forms a dense single species stand that effectively inhibits and eliminates other plant species.

Phragmites australis (Cav.) Trin. ex Steud. (=Phragmites communis Trin.), common reed, roseau commun
An invasive genotype of common reed, growing up to 18 feet (6 metres) high, was first introduced into North America from Europe about 1910 and is now naturalized throughout the United States and southern Canada. This introduced genotype is taller and more vigorous than our native genotype, and it has largely supplanted the native in many habitats. The European introduction of common reed has now become very invasive. Its below-ground rhizomes allow it to spread vigorously, and to form very large and dense clones that smother out all other vegetation.

Poa annua L., annual blue grass, pâturin annuel This introduced grass, typically an annual or winter annual, will normally die after it produces seed. Greens-keepers usually taken to stop seed production when it is utilized as a golf-green turf-grass. Annual blue grass plants will often form dense clumps with flowering stems from 3 to 12 inches (8 to 30 cm.) tall. Its leaves are a lighter green than the leaves of Kentucky blue grass and it lacks the underground rhizomes of that grass. Annual blue grass reproduces solely by seed. It grows in a wide range of disturbed habitats both within and outside of our area. It has the ability to tolerate close mowing, making it a particularly troublesome weed in lawns and in turf-grass.

Poa pratensis L., Kentucky blue grass, pâturin des prés It is a widespread perennial grass, with flowering stems from 4 to 12 inches (10 to 30 cm.) high. Its roots and rhizomes are mostly in the top 3 inches (7.5 cm.) of the soil. Both native and introduced populations occur within and outside of our area. It can be a native or cultivated plant, a weed or even an invasive plant. It is one of our most popular lawn grasses, being able to withstand mowing and considerable periods of drought.

Setaria pumila (Poir.) Roem. & Schult.- yellow foxtail, sétaire glauque
An annual plant, with fibrous roots, that reproduces only by means of its seeds. Stems are erect, reaching 3 feet (9 dm.) in height. It is a weed of agronomic crops, turf, of landscapes and of nurseries. Its spikelets have bristles that turn yellow at maturity and the seed head resembles a fox’s tail, thus its name. Found throughout our area, but is most abundant near the west coast and east of the great lakes. Introduced from Europe.

Setaria viridis (L.) P.Beauv., green foxtail, sétaire verte
Annual, reproducing by seeds; flowering stems from 3 inches to 3 feet (8 cm. to 9 dm.) long; grainfields, gardens, roadsides, and waste places; introduced from Europe. Present throughout our area and is generally more abundant than yellow foxtail. It has become a major pest in the Midwest.

Click on a photo to view an enlarged image.
Weed Name Photo Weed Name Photo
wild oats, folle avione wild oats, folle avione
wild oats, folle avione
(germinating seedlings, FF)
wild oats, folle avione (NC)
wild oats, folle avione
(F&M)
smooth brome, brome inerme
downy brome, brome des toits downy brome, brome des toits
(seedling)
downy brome, brome des toits
(F&M)
     
smooth crab grass, digitaire astringente
(A, plant; B, front of spikelet with minute first glume at base; C, back of spikelet entirely covered by second glume; D, seed; E, junction of leaf blade and sheath), and large crab grass, digitaire sanguine ( F, front of spikelet with first glume at base; G, back spikelet about half covered by second glume; H, junction of leaf blade and sheath: from C. Frankton and G. A. Mulligan 1987, Weeds of Canada, Publication 948, Agriculture Canada, Ottawa, Ontario, 217 pp.)
smooth crab grass, digitaire astringente
smooth crab grass, digitaire astringente smooth crab grass, digitaire astringente
(herbarium specimen)
smooth crab grass, digitaire astringente
(vegetative)
smooth crab grass, digitaire astringente
large crab grass, digitaire sanguine large crab grass, digitaire sanguine
(in fruit)
barnyard grass, échinochloa pied-de-coq
(A, plant; B, spiklet; C, spikelet with empty glumes removed exposing the seed): from C. Frankton and G. A. Mulligan 1987, Weeds of Canada, Publication 948, Agriculture Canada, Ottawa, Ontario, 217 pp.)
barnyard grass, échinochloa pied-de-coq
barnyard grass, échinochloa pied-de-coq barnyard grass, échinochloa pied-de-coq
barnyard grass, échinochloa pied-de-coq quack grass, chiendent commun
quack grass, chiendent commun quack grass, chiendent commun
(herbarium plant with rhizomes)
quack grass, chiendent commun
(fruiting spike)
quack grass, chiendent commun
(germinating seedlings, FF)
quack grass, chiendent commun
(NC)
quack grass, chiendent commun
(F&M)
foxtail barley, orge queue-d’écureuil foxtail barley, orge queue-d’écureuil
(germinating seedlings, FF)
foxtail barley, orge queue-d’écureuil
(NC)
foxtail barley, orge queue-d’écureuil
(F&M)
Persian darnel, ivraie de Perse Persian darnel, ivraie de Perse
(seedlings, FF)
witch grass, panic capillaire
(F&M)
witch grass, panic capillaire
witch grass, panic capillaire
(herbarium specimen)
witch grass, panic capillaire
(seedlings)
reed canary grass, alpiste roseau
reed canary grass, alpiste roseau
reed canary grass, alpiste roseau
common reed, roseau commun
common reed, roseau commun
common reed, roseau commun
(in roadside ditch)
common reed, roseau commun
(inflorescences, in nature)
common reed, roseau commun
(inflorescence, pressed)
     
annual blue grass, pâturin annuel annual blue grass, pâturin annuel
annual blue grass, pâturin annuel
(mature spikes)
annual blue grass, pâturin annuel
(seedling)
Kentucky blue grass, pâturin des prés Kentucky blue grass, pâturin des prés
Kentucky blue grass, pâturin des prés green foxtail, sétaire verte
green foxtail, sétaire verte green foxtail, sétaire verte
(germinating seedlings, FF)
green foxtail, sétaire verte (NC) green foxtail, sétaire verte
(A, plant; B, junction of leaf blade and sheath showing ligule; C, spikelet; D, seed), and
yellow foxtail, sétaire glauque
(E, head; F, spikelet; G, seed; H, leaf blade showing long hairs at base; I, junction of leaf blade and sheath): from C. Frankton and G. A. Mulligan 1987, Weeds of Canada, Publication 948, Agriculture Canada, Ottawa, Ontario, 217 pp.)
Foxtail seeds:
top, yellow foxtail, sétaire glauque;
middle, green foxtail, sétaire verte;
bottom, giant foxtail, sétaire géante
(photos by Stephen J. Darbyshire)