Grasses & Grass-Like Pacific Northwest Weeds

Cheatgrass germinates and grows throughout fall and winter and spring following sufficient precipitation. Plants grow to 4-30 inches tall, depending on available soil moisture and fertility.

Cheatgrass flowers in spring. Flowers are small and grow in nodding, hairy bunches (inflorescences) 3 to 9 inches long. Flowers turn a reddish-brown color as shown in the photo.

Individual cheatgrass plants may produce dozens to hundreds of seeds. Most seeds germinate the following fall. Seeds remain viable in the soil for up to 5 years.

Seeds stick to shoes, clothing, and pets. They are easily transported to new areas.

Leaf blades are narrow. They grow up to 0.2 inches wide.

Plants grow 2 to 20 stems that have soft, short hairs on the lower half of the stem (leaf sheath).

False brome germinates in late fall and spring. Plants mature into compact bunches of bright-green leaves throughout spring, summer, and fall. Plants remain green in mild winter temperatures, and in some colder winter locations, the leaves and stems die and become white thatch.

Individual false brome plants produce dozens to hundreds of seeds. Seeds are spread by animals, people, or equipment that move through infested areas. Most seeds germinate within a year or two.

False brome flowers in summer. Groups of flowers grow in pale green, drooping spikelets that are attached directly to the flowering stem. Spikelets are 1-2 inches long. There are 5-10 spikelets per flowering stem, as shown in the photo. Each spikelet has 7-17 individual flowers.

False brome is expanding quickly in closed-canopy forests, woodlands, oak savannah, grasslands, roadside trails, and disturbed areas.

It degrades habitat by suppressing native plant understory growth.

False Brome Distribution & Reporting

Red areas show Oregon counties where false brome is widespread. Yellow areas show counties where it has limited distribution. It is not known to occur in the grey areas.

Reporting in Oregon

You can help Oregon agencies track the distribution of invasive species.

If you have false brome growing on your property, please report it to the Oregon Invasive Species Hotline. Call 1-866-INVADER (1-866-468-2337). Or use their online reporting form.

Johnsongrass grows up to 8 feet tall. It thrives in disturbed areas. It is most often found in croplands, rangeland, drainage ditches, roadsides, and riparian areas.

Mature grass blades are flat with a prominent white midrib. Blades are 12 to 30 inches long and ½ to 1 inch wide. The round stems stand upright and are hairless and sparsely hairy where the leaf blade meets the stem.

Johnsongrass has a papery flap of material called the ligule. It grows from where the leaf blade connects to the stem (leaf sheath). Ligule growth is variable. It can be intact and ¼-inch long or hidden, or show as fringe.

Flowers grow in pyramid- or cone-shaped flower heads from late spring to early fall. They range from purple-brown to golden to pale green.

Johnsongrass flower heads form abundant fruits and then seeds that spread to new locations.

Seedlings closely resemble corn seedlings. They are similar to rhizome sprouts.

This perennial grass grows creeping rhizomes (roots) to form a dense clump.

Johnsongrass Distribution & Reporting

Yellow areas show counties where Johnson has limited distribution. Green areas show where it once grew but has been eliminated. Grey areas show counties where it is not known to occur.

Report Invasive Species

You can help Oregon agencies track the distribution of invasive species.

If you have an infestation of Johnsongrass on your property, please report it to the Oregon Invasive Species Hotline. Call 1-866-INVADER (1-866-468-2337). Or use their online reporting form.

Jubatagrass grows in moist, cool coastal areas. It is found in dunes, drainage ditches, roadsides, cut slopes, forestry operations, and disturbed areas.

Mature leaves are 0.8-1.2 inches wide and grow 3-6 feet above the ground. Bright-green leaves ascend and spread horizontally compared to pampasgrass. The blades are flatter and less coiled compared to pampasgrass.

Immature jubatagrass flowering plumes are deep violet and can grow 3-6 feet above leaves. Plumes occur in late summer-early fall.

Mature jubatagrass flowering plumes fade to pinkish or tan color. Jubatagrass flowers are effectively all female; however, plants produce viable seeds. Each jubatagrass flowering plume can create roughly 100,000 seeds. An individual plant creates millions of seeds yearly. Seeds are less than 0.1 inches long and are dispersed on air currents, animals, clothes, and equipment.

Seeds live less than six months and require moist bare ground in spring to germinate and grow new plants. Seedlings compete poorly with native plants in shady conditions.

Mature jubatagrass forms a robust root system that often needs heavy equipment to remove.

Pampasgrass is often grown in landscapes. In comparison to jubata grass, pampasgrass plants grown in landscapes don’t always create viable seeds. If you have pampasgrass in your landscape, look for new seedlings in bare-ground areas. If you don’t see new seedlings, then you can leave the plants alone. If you do see new seedlings, then remove the pampasgrass plants from your landscape.

Immature female pampasgrass flowering plumes are white and grow 0-3 feet above leaves. The male flowering plumes are white-violet and grow 0-6 feet above leaves. Plumes occur midsummer-early fall. The immature plumes of jubata grass are violet-colored in comparison.

When both male and female pampasgrass flower heads grow together, they form viable seeds. In this case, it spreads to new areas, which makes it an invasive plant species. Pampasgrass grows in moist, cool coastal areas. It tolerates a wider range of cool and warm temperatures compared to jubatagrass. Pampasgrass grows in the increased sunlight intensity and drought found at inland sites. It is found in dunes, drainage ditches, roadsides, cut slopes, forestry operations, and disturbed areas.

Jubatagrass Distribution & Reporting

Red areas show Oregon counties where jubatagrass is widespread. Yellow areas shows counties where it has limited distribution. Gray areas show counties where it is not known to occur.

Report Invasive Species

You can help Oregon agencies track the distribution of invasive species.

If you observe an infestation of jubatagrass or pampasgrass on your property, please report it to the Oregon Invasive Species Hotline. Call 1-866-INVADER (1-866-468-2337). Or use their online reporting form.

Quackgrass grows 1-4 feet tall. It thrives in disturbed areas. It is often found in croplands, moist meadows, lawn drainage ditches, roadsides, and along creeks and rivers.

Stems grow horizontal from the base of the plant then bend upwards. Leaves are flat and ¼-½ inch wide, 4-12 inches long. The leaves get narrow 1 to 2 inches behind the tip.

Once seedlings establish, rhizomes spread to increase the size of the patch.

Quackgrass has two clasping structures called auricles. They grow from where the leaf blade connects to the stem (leaf sheath). The auricles are narrow, often claw-like. Their color is pale green to pale purple as shown in the photo.

Flowers grow on a flattened spike that is 2-10 inches long. Flowers appear from late spring through summer and produce a few dozen seeds per plant. Seeds are viable for 1-6 years.

Quackgrass seeds grow into new plants.

Seedlings look like mature plants, but auricles may not be developed. Young plants grow rhizomes when 6 to 8 above-ground stems are present.

Reed canarygrass grows up to 8 feet tall. It grows in agricultural fields, drainage ditches, roadsides, and natural areas.

Mature grass blades are ¼-⅓ inch wide and up to 14 inches long. The blades taper toward the tip. The round stems stand mostly upright, and by mid to late summer some stems may lean down to the ground. The stems are hairless.

Flowers are densely clustered spikes up to 12 inches long, as shown in the photo. They often have dark-green or purple streaks.

Reed canarygrass has a papery, 1/8-1/4-inch-long flap of material (ligule). It grows from where the leaf blade connects to the stem (leaf sheath).

Reed canarygrass flower heads create thousands of seeds that easily disperse, and lead to new plants.

Seeds germinate to form new plants.

Reed canarygrass forms a robust, spreading root system. It forms dense patches.

The mature leaves are 2–3 feet long, flattened and sword-shaped, typical of most iris. They may stay evergreen in mild winters.

Yellow flag iris flowers have 3 large downward-spreading sepals and 3 small erect petals. The sepals may have delicate brownish to purple veins. Yellow color may be bright or pale. It blooms from late spring into summer.

The seed pod is up to 4 inches long and glossy green. It contains many flattened brown seeds. Seeds float on the water, and spread yellow flag iris into the surrounding area.

Yellow flag iris spreads by stout rhizomes. They grow rapidly, forming a dense mat.

Flattened brown seeds are about ¼ inch in diameter.