Rye brome (Bromus secalinus)

Synonyms: Serrafalcus secalinus, Bromus mollis var. secalinus, Bromus secalinus var. velutinus, Festuca secalina

Common Names: Cheat, chess, rye chess

Description:

Rye brome (Bromus secalinus) is an annual grass in the grass family, native to Europe, the Mediterranean, and western Asia [1][2]. It reached North America centuries ago as a contaminant mixed into imported cereal seed and is now found across most of the United States and southern Canada [1][5]. MISIN tracks it because it is a weed of small-grain crops and hayfields that travels in contaminated seed, hay, and soil, and it has been spreading again as farming has shifted toward reduced tillage [5].

Habit:

Rye brome is a clump-forming annual grass, usually 8 inches to about 2.5 feet tall (20?80 cm) [4]. Its leaf blades are narrow ? about 1/8 inch wide ? and softly hairy, and the leaf sheaths (the part that wraps the stem) are also hairy and joined into a closed tube [4]. The seed head is an open, branching cluster that nods or arches to one side as the seeds fill and ripen [4].

The most reliable clue is the shape of the spikelets ? the small seed-bearing packets at the branch tips. In rye brome they are plump and egg-shaped, roughly 1/2 to 3/4 inch long, and hold 4 to 10 seeds each [4]. As they ripen, the individual seed cases (lemmas) thicken and roll their edges inward, so they look rounded and slightly separated from one another rather than flat and overlapping [4]. The bristle (awn) at the tip of each seed case is short ? about 1/8 inch (3 mm) ? or sometimes missing altogether [4]. That short-to-absent awn separates it from most other weedy bromes, which carry long, obvious bristles.

Look for it from late spring into early summer, when the plants send up their nodding seed heads ? often right alongside a wheat, rye, or hay crop, or on roadsides and field edges. This is also the window when seeds are forming but not yet shed, which is the time to act.

At-a-glance cues:

1. Clump-forming annual grass, 8 inches to about 2.5 feet tall, with soft-hairy leaves and closed, hairy leaf sheaths [4]
2. Open seed head that nods or arches to one side as seeds ripen [4]
3. Plump, egg-shaped spikelets about 1/2 to 3/4 inch long, each with 4 to 10 seeds [4]
4. Very short awns (about 1/8 inch) or none ? unlike the long bristles of most weedy bromes [4]

Leaves:

1. Arrangement: alternate along the stem, with 4 to 8 leaves per stem [4]
2. Blade: flat and narrow, about 1/8 inch (2?4 mm) wide and several inches long [4]
3. Surface: softly hairy to slightly rough [4]
4. Sheath: wraps the stem as a closed tube and is hairy, without blister-based hairs at the base [4]
5. Ligule: a small membrane about 2?3 mm long where the blade meets the sheath [4]

Stems:

1. Habit: erect, unbranched flowering stems (culms) rising from a basal clump [4]
2. Life cycle: annual ? the plant grows, sets seed, and dies within a single year [4]
3. Height: 8 inches to about 2.5 feet (20?80 cm) [4]
4. Roots: fibrous and shallow, with no creeping underground stems [4]

Flowers:

1. Seed head: an open, branching cluster (panicle) that nods or arches to one side, roughly 2 to 9 inches long [4]
2. Spikelets: plump and egg-shaped, about 1/2 to 3/4 inch (10?20 mm) long, each holding 4 to 10 florets [4]
3. Seed cases (lemmas): thicken and roll their edges inward as they ripen, looking rounded and slightly separated [4]
4. Awns: short, about 1/8 inch (3 mm), straight, or sometimes absent [4]
5. Bloom time: late spring into early summer [4]

Fruit and seeds:

1. Fruit: a dry grain (caryopsis) enclosed in the seed case, one per floret [4]
2. Shape: linear to oblong, plump [4]
3. Output: each plant can carry many spikelets of 4 to 10 seeds, producing a large seed crop [4]
4. Dispersal: seeds travel mainly in contaminated crop and grass seed, in hay and straw, in soil, and on equipment ? not on the wind [5]

Habitat:

Rye brome is native to Europe, the Mediterranean region, and western Asia [1][2]. In North America it is now found across most of the United States and into southern Canada [1].

It is a plant of open, sunny, disturbed ground. It grows mostly in and around small-grain crops ? winter wheat and rye especially ? and turns up in hayfields, pastures, meadows, abandoned fields, field edges, vacant lots, roadsides, railways, and other waste places [4][5]. It favors the loose, regularly disturbed soil of farmed and developed land and does not typically push into healthy, undisturbed native plant communities [5].

Reproduction:

Rye brome spreads only by seed ? it has no creeping roots or runners [4]. For a homeowner or land manager, that means it almost always arrives from outside: mixed into cheap or uncertified grass seed, carried in hay or straw, moved with fill soil, or hitchhiking on mowers and farm equipment [5]. Once a plant sets seed on your property, the next generation comes up right where the seed fell.

It behaves as a winter annual over much of its range. Seeds sprout in fall, the young plants overwinter as low tufts of grass, and they bolt, flower, and ripen seed in late spring and early summer ? maturing at about the same time as a winter cereal crop, which is part of why it travels so easily with grain [5]. Some seeds also sprout in spring. Each plant can produce a heavy crop of seed from its many spikelets [4].

The timing that matters for control is simple: cut, pull, or bag the seed heads before the seed ripens and drops in early summer. Stopping seed set for a season or two, and not bringing in new contaminated seed or hay, is what shrinks a patch ? because the whole population resets from seed each year.

Impact and Damage:

Rye brome's clearest impact is on farms and in newly seeded ground. It is one of the more troublesome grass weeds of winter wheat and winter rye, where it competes with the crop and lowers both the yield and the quality of the harvested grain [5]. Its seed contaminates crop seed and hay, which is how it moves from one field or property to the next [5]. For a homeowner, that translates into a weedy grass that can come in with bargain grass seed, straw mulch, or hay and take over a patch of thin new lawn or a garden edge. It is not known to be toxic to people, pets, or livestock.

After nearly disappearing from farm fields in the late 20th century ? thanks to better seed-cleaning ? rye brome has re-emerged as a cereal weed in recent decades. Researchers link the comeback to simpler crop rotations and the wider use of minimum tillage, which leaves seed near the surface to sprout [5]. Making it harder to manage, populations resistant to a common group of weed-control chemicals have now been confirmed, part of a broader pattern of herbicide resistance documented across the brome grasses worldwide [6].

Its impact on natural areas is limited compared with aggressive invaders. Rye brome is tied to disturbed and cultivated ground and rarely dominates intact native plant communities [5]. MISIN tracks it so that new occurrences and any spread beyond farmland are recorded early, but its main harm is agricultural and economic rather than a broad threat to wild habitats.

Similar species:

Rye brome is one of several weedy brome grasses that are easy to mix up. The quickest thing to check is the awn ? the bristle at the tip of each seed case: rye brome's is very short or absent, while most look-alikes have long, obvious bristles.

Cheatgrass (Bromus tectorum) is a winter annual like rye brome and often grows in the same disturbed places, but its seed head is soft, densely hairy, and droops in a slender one-sided spray, and each seed case carries a long bristle up to about 3/4 inch [4]. Rye brome's plump, nearly awnless spikelets set it apart.

Smooth brome (Bromus inermis) is a perennial that spreads by creeping underground stems and forms a dense sod, unlike rye brome's single-season clumps with no runners [4]. Smooth brome is mostly hairless with a narrow, upright seed head and little or no awn; if the grass comes back from spreading roots year after year, it is not rye brome.

Japanese brome (Bromus japonicus) is another annual weed of fields and roadsides, but its seed cases are flatter and thinner and carry longer bristles, roughly 1/3 to 1/2 inch, that often twist or bend outward as they dry [4]. Rye brome's seed cases are thicker and roll inward, with only a short awn.

Field brome (Bromus arvensis) also resembles rye brome, but its florets are flat and thin rather than plump and inrolled, and it has longer awns and a longer, hairier ligule where the leaf meets the stem [4]. Checking whether the seed cases are rounded-and-inrolled (rye brome) or flat-and-long-awned (field brome) tells them apart.

Monitoring and rapid response:

Signs to watch for:

1. From late spring into early summer, clump-forming grass 8 inches to 2.5 feet tall with open, nodding seed heads [4]
2. Plump, egg-shaped spikelets about 1/2 to 3/4 inch long with very short awns or none [4]
3. Soft-hairy leaves and closed, hairy leaf sheaths [4]
4. New patches in thin or newly seeded lawn, garden edges, hayfields, field margins, and roadsides ? often traceable to bargain grass seed, straw, or hay [5]

What you can do:

1. For a small patch, pull or dig the plants out ? roots come up easily since there are no runners [4]. Do it before the seed ripens in early summer.
2. If you cannot pull it all, cut or mow the seed heads off before the seed matures and bag them; this stops that year's seed even though it will not kill an already-rooted plant [5].
3. Because the whole population resets from seed each year, stopping seed set for one or two seasons and preventing new seed from arriving does most of the work.
4. Use only clean, certified grass seed, and avoid spreading hay, straw, or fill soil from an area you know is infested ? seed travels in all of them [5].
5. Clean mowers, tillers, and other equipment after working an infested spot so you do not carry seed to clean ground [5].
6. For a larger site, natural area and farm crews can treat it across a field by mowing or cutting before seed set on repeat visits, prioritizing small outlying patches first so they do not seed into clean areas.

When to call a professional:

1. Large or well-established infestations in cropland or hayfields, where a multi-season plan is needed and hand methods cannot keep up.
2. Situations where the grass keeps returning despite repeated removal, which may signal a heavy seed bank or a herbicide-resistant population [6].
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. USDA NRCS Plants Database. Bromus secalinus L. (rye brome), symbol BRSE. plants.usda.gov
2. Plants of the World Online. Bromus secalinus L. Royal Botanic Gardens, Kew. powo.science.kew.org
3. Integrated Taxonomic Information System. Bromus secalinus L., TSN 40519. itis.gov
4. Native Plant Trust, Go Botany. Bromus secalinus (rye brome). gobotany.nativeplanttrust.org
5. Pytlarz E, Gala-Czekaj D (2022). "Possibilities of using seed meals in control of herbicide-susceptible and -resistant biotypes of rye brome (Bromus secalinus L.) in winter wheat." Plants 11(3):331. semanticscholar.org
6. Ribeiro VHV, Barroso J, Brunharo CACG, Mallory-Smith C (2023). "Herbicide resistance in Bromus spp.: a global review." Weed Science 71(5):422?437. semanticscholar.org

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