Rough Bluegrass
We periodically get inquiries concerning areas in tall fescue and bluegrass lawns that are about 12 to 18 inches in diameter and light green in color. Some people think this is a disease problem such as cool season brown patch. The problem in most instances is Poa trivialis or rough bluegrass.
This
perennial grass is light green in color and has soft shiny leaf blades. To identify rough
bluegrass, look for aggressive stolons, or runners, and oblong seed-heads like Kentucky bluegrass.
It is grainy in appearance, that is, the leaves have a tendency to lie flat in one direction.
This grass thrives when cool, moist conditions prevail, and when management is high. There is no selective herbicide control. The clumps become less noticeable after the weather warms and the rain stops. Each clump probably originated from a single seed so it doesn't take much seed to cause a problem.
It is highly unlikely that the large clumps are the result of recent seeding because the plants would not be that large. Chances are the plants have been present for several years and have gone unnoticed, until the environmental conditions favor its growth. Because tall fescue seed is much larger, seed blends that are exclusively tall fescue do not usually contain Poa trivialis.
Rough bluegrass (Poa trivialis L.) is a yellowish-green grass with soft leaf blades which are glossy beneath and have a narrow boat-shaped tip. It spreads by stolons and forms dense, thick patches. The leaf blades are upright at first, but tend to lay down and mat as the patches become older. Because the root system is shallow, the patches are easily pulled up in tufts or clumps.
General Characteristics
Rough bluegrass is capable of forming a reasonable turf under certain limited environmental conditions and careful management. It is fine-textured turfgrass developing a high shoot density under cool, moist conditions. It is capable of withstanding a considerable amount of shade if sufficient moisture is present.
It is one of the most winter hardy turfgrasses with very good low temperature tolerance. The major weaknesses of rough bluegrass include poor wear, drought and high temperature tolerance.
It is sometimes included in a seed mixture with Kentucky bluegrass because of its shade tolerance. However, due to its tendency to produce bright yellow-green patches, it does not blend well with Kentucky bluegrass.
It responds vigorously to fertilizer and irrigation, and under conditions where water is supplied too frequently, it becomes intolerably aggressive and smothers out the Kentucky bluegrass.
During July and August patches of rough bluegrass wilt and brown-out markedly unless careful attention is paid to its water requirements.
Mowing
Mow at 1 - 2.5 inches.
Fertilizing
Fertilize during the period of active growth (March - June; September - November).
Planting
Seed at 1 - 3 lbs. seed/1000 sq. ft.
Irrigation
Water frequently.
Special problems
Susceptible to most turfgrass insects and diseases
Very low drought tolerance
Low heat tolerance
Very low traffic tolerance
Controls as a weed
Where rough bluegrass has invaded a Kentucky bluegrass home lawn, it is usually desirable to remove it. The following have provided some limited control:
