Roughstalk bluegrass. Photo: Mira Talabac, University of Maryland Extension

Roughstalk bluegrass (Poa trivialis), the light green patches in a residential lawn. Photo: Miri Talabac, University of Maryland Extension

Updated: May 5, 2021

A weedy species of bluegrass called roughstalk bluegrass, (Poa trivialis) is fast becoming a common grassy weed in Maryland lawns. It is most noticeable in the spring. Problematic in home lawns because the growth habit outcompetes and grows faster than more desirable grasses.  It is a lighter green color and doesn’t blend well with mown turf since it has a finer texture and has noticeable, fast-growing seed heads.

Life cycle

Perennial, cool-season grassy weed. Thrives in early spring and fall. 

Growth habit 

Forms light green patches that are evident early in the season. They can turn brown and go dormant in the heat of the summer. Grass blades can often look shiny. Stalks can turn red at the base as it grows. Aggressive, clumping spreader. 

Reproduction

Often it comes in as a seed contaminant in grass seed mixes. It spreads by reseeding from established plants as well as by aggressive horizontal stolons.

seed head of rough stalk bluegrass
Seed head produced by Poa trivialis
Photo: David L. Clement, University of Maryland Extension

Conditions that favor growth

It prefers and spreads quickly in semi-shady conditions in compacted, poorly drained, moist soils (often begins in drainage swales).  Although once established, it will spread into sunnier, drier sites.  Poa trivialis also tends to die out during the heat of the summer months leaving thin areas in the turf before re-growing in the cooler fall season

roughstalk bluegrass coming out of dormancy
Roughstalk bluegrass coming out of dormancy and beginning
to grow in early spring
roughstalk bluegrass ligule
Roughstalk bluegrass has a membranous ligule.
Photo: David L. Clement, University of Maryland Extension

Management in lawns

Cultural lawn care practices

Maintain healthy, dense turf that can compete and prevent weed establishment.

Mechanical management

Small infestations can be dug out; must remove all parts of the root. Rent a sod cutter to remove large patches. Then reseed. 

Chemical treatment in lawns

Perennial grasses growing out of place in lawns are extremely difficult to control selectively in turfgrasses. Cannot be effectively controlled by any of the herbicides currently on the market. Total lawn renovation or killing the patches using glyphosate (an ingredient in a non-selective herbicide) and then reseeding will slow it down but because of the vast seed bank in the soil and stolons, it will return.

Additional resource

NC State Poa trivialis (good for identification)

Turfgrass Science at Purdue University | Roughstalk bluegrass