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Downy Brome

Downy brome (Bromus tectorum L.), Japanese brome (Bromus japonicus Thunb. ex Murr)

Stems: Annual bromes grow until the stems are erect and slender. Even the swollen nodes on the stem are covered with soft straight hairs. The jagged ligule is one to three mm (1/8 to 1/4 in.) in length.

Growth: Growth is rapid, beginning very early in the spring, often from plants germinating the previous fall and producing mature seed two months later around mid-June. Downy brome often grows in large tufts and resembles a miniature smooth brome grass plant except it is very pubescent.

Once the inflorescence has emerged, there are both gross and specific characteristics that will distinguish downy and its relative, Japanese brome, from each other. The inflorescence is a many branched panicle which droops to one side.

Japanese brome, also found in Saskatchewan, is slightly different than downy brome, and is compared below:

Plant Characteristic Downy brome Japanese brome
Growth Winter annuals, spring annuals, or biennials Both winter and spring annuals
Maturity Appearance Purplish-red (whole plant) Pale tan (whole plant)
Vegetative State Delicate More delicate than the downy variety
Leaves 2 - 4 mm wide 1 -3 mm wide
Inflorescence The panicle droops and the upper spikelets are pointed downward Less drooping of the upper spikelets
Spikelets 2 - 3 cm long, very hairy 1 - 2 cm long, very hairy
Glumes (outer-most layer of the seed) The first glume: one nerve

The second glume: three nerves
The first glume: three nerves

The second glume: five nerves
Seeds Grey to purple in colour

Tipped with a straight awn 12 - 17 mm (0.5 - 0.75 in.) Awns are typically longer than the seed itself.
Tan in colour

Tipped with a curved awn 8 - 10 mm (0.3 - 0.4 in.), protrude 90 degree from the axis of the spikelet. Awns are typically shorter than the seed itself.


By seeds only.

Historical Use

Downy and Japanese brome plants have no historical uses. Livestock, deer and antelope can get fair to good forage value out of annual bromes in spring prior to flowering. They are actually a major forage source in part of the north western United States, supplying the bulk of early spring forage for all livestock classes. It is the principal feed source on all spring lambing ranges and supplies good quality forage for a short term.

Downy brome remains green and palatable for about a month in both spring and fall. Japanese brome may remain palatable slightly later in the season.


Annual bromes can be found in:

  • Annual cropland,
  • Rangeland, and
  • In industrial sites or waste areas.

In undisturbed areas, they are typically an indicator of poor range condition. They readily invade where the native vegetation has been disturbed by overgrazing, fire, cultivation, etc. Since they do not compete well with perennial grass, it is not normally present in range in good condition. Annual brome has spread over native range, pasture land, disturbed soils and forests throughout the western United States.

In Canada, mixed populations of downy and Japanese brome can be found in southwestern Saskatchewan and Alberta, and plants can be found in isolated areas through to the Peace River in Alberta. Manitoba has recently identified isolated fields with heavy infestations of each.

Mixed infestations of downy and Japanese brome are not uncommon in the brown and dark brown soil zones of Saskatchewan. Japanese brome is adapted to somewhat moister habitats than downy brome and, as a result, has been reported in isolated populations in moister regions of the province such as Biggar, Liberty, Duval and Nipawin.


Since its life cycle terminates relatively early in the season, uncontrolled downy brome is a fire hazard and is extremely flammable, allowing fires to kindle and spread rapidly. Range infested with annual brome species experiences a drastic shortening of the normal prairie fire cycle, resulting in a change of species composition that favours the persistence of annual bromes and other fire tolerant species.

The rough awns of downy brome can puncture the soft tissues of the mouth, nostrils and eyes of livestock; perforation of the intestines has also been reported. This occurs when livestock graze mature plants or consume hay with high proportions of downy brome. In the United States, the term "rip gut" is used when the seeds perforate the intestines and the animals die. The presence of awns also reduces feed intake.

Downy brome uses moisture from shallow layers in the soil. This directly influences the establishment of other desirable grasses, especially perennials.

Downy brome can contaminate the fleece of fibre producing livestock.


Once annual bromes dominate an area they are difficult to eradicate, but eradication has been achieved in certain situations with diligence. With a short lived seed, these plants must produce seed each year in order to perpetuate the infestation. Therefore, to control infestations, it is imperative to prevent all seed production. Mowing large infested areas just as the majority of the panicles begin to emerge is one method to reduce seed set.

There are no herbicides registered in Canada to manage annual brome infestations in perennial grass forages. Trifluralin is available for establishing pure legume stands only. Research in the United States has indicated that the Group 1 grass control products for broadleaf crops (Assure, Venture, Poast and Select) have provided good to excellent control of Japanese brome and suppression of downy brome at the highest labelled rates when applied while still in the seedling stage (prior to tillering or stem elongation).

In annual cropland, fall harrowing is another method to stimulate the germination of seed in the fall, followed by spring tillage or glyphosate to control spring seedlings and over-wintered plants.

For smaller infestations hand-roguing is the best way to remove plants prior to seed set. A pipeline company in the Swift Current area found that they eradicated a population from a significant length of right-of-way within a three to five year period using this method.

Note: If seed has already set prior to roguing, remember the seeds will work their way through woven poly bags, so line them with garbage bags first. When buying forage seed, make sure to ask for and read the certificate of analysis prior to purchase. Always request downy brome free seed and accept nothing less. Try to maintain pastures in good to excellent condition.

For available herbicide and rates, consult the provincial Guide to Crop Protection.

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