Supina bluegrass

What is supina bluegrass?

Supina bluegrass (Poa supina) is a cool-season perennial native to the Alps. Unlike Kentucky bluegrass, which spreads underground, supina bluegrass spreads by thick stolons along the soil surface that root at each node.

Its fans like it for two things: it stands up to heavy wear and compacted soil, and it grows in moist, dense shade. German experience suggests even a small share of supina in a seed mix can take over a heavily used field after several years (MSU).

The downsides are real. University of Wisconsin says seed can cost up to 10 times more than common lawn seed, the color is light, thatch builds quickly, it needs low mowing, and it does poorly in drought and heat. Seedheads show up for 2 to 4 weeks each spring.

How to identify supina bluegrass

Pull up a few shoots and look closely where the leaf blade meets the stem. Here is what to check on supina bluegrass:

• Vernation: Folded in the bud.
• Ligule: Short, flat and thin, usually only a bit longer than Kentucky bluegrass. On seed stalks it is long and rounded.
• Leaf blade: Smooth, soft and hairless; about the size of a Kentucky bluegrass leaf.
• Seedhead: Appears each spring, usually early to mid-May, over 2 to 4 weeks, with purple seed coverings. Annual bluegrass heads are white.
• Growth habit: Thick stolons that root at the nodes and form dense turf.

Where supina bluegrass is grown in the US

Supina bluegrass has been used in Europe for more than 30 years and is getting more attention in the northern US and Canada, says University of Wisconsin Extension. MSU researchers note that Germany and other European countries have long valued it for wear tolerance, disease resistance and its ability to take over a stand.

Its two niches are heavy traffic and moist, dense shade. Wisconsin calls it excellent for soccer fields and among the best choices for shady, moist sites, growing in up to 90 percent shade. UMass lists it as a grass under study for very high-traffic areas such as athletic fields. The University of Minnesota lists it with rough bluegrass as an option for dense shade with plenty of moisture, but warns the seed is expensive.

It is not for dry or hot places. Wisconsin says not to plant it in dry areas or south of its suggested range, and to use fine fescues instead for dry shade.

Supina bluegrass pros and cons

Pros

• Thrives in heavy traffic and on compacted soil
• Grows in moist, dense shade
• Excellent cold tolerance and early spring green-up
• Few disease problems
• Often has fewer weeds than other cool-season grasses
• Only a little seed is needed because it spreads fast

Cons

• Seed can cost up to 10 times more than common lawn seed
• Light green color; looks patchy in mixes at first
• Thatch builds quickly
• Needs lower mowing than most cool-season grasses
• Poor drought and heat tolerance
• Stolon pieces can spread on mowers and aerators

Grasses that look like supina bluegrass

How and when to plant supina bluegrass

Ways to plant: Seed, alone or in mixes. A few growers sell sod, pure or mixed with Kentucky bluegrass (University of Wisconsin).

Seeding rate: 0.5 to 1.25 lb per 1,000 sq ft alone. Mixes with 5 to 25 percent supina: 1 to 2 lb with Kentucky bluegrass, or 4 to 8 lb with perennial ryegrass (University of Wisconsin).

When to plant: Mid-August to mid-September in Wisconsin (University of Wisconsin). Broadcast or drill seed about 1/4 in. deep.

Seeding dates change from state to state. See when to plant grass seed by state, or our Pennsylvania grass seed guide if you are in PA.

How to care for supina bluegrass

Mowing: Mow at 0.75 to 1.5 in. in sun and up to 2.5 in. in heavy shade. Reel or rotary mowers both work. Mulch-mow; the clippings break down fast and do not add to thatch (University of Wisconsin).

Watering: Give 1 to 1.5 in. of water per week in one or two waterings for medium to high quality, using the higher amount above 80°F or in wind. Sandy soil needs water more often. Do not water to the point of runoff (University of Wisconsin).

Fertilizing: Match nitrogen to soil, traffic and mowing height, from about 2 to 8 lb per 1,000 sq ft per year. Use a blend of quick- and slow-release nitrogen, and apply potassium at a 1:1 to 1:2 ratio with nitrogen (University of Wisconsin).

Nitrogen per year: About 2 to 8 lb N per 1,000 sq ft per year, depending on soil, traffic and mowing height. Loam or clay with light traffic: 2 lb if mowed above 1.5 in., 4 lb below. Sandy soil with heavy traffic: 6 to 8 lb (University of Wisconsin).

Overseeding: Mixes usually hold 5 to 25 percent supina by weight. Wisconsin does not recommend mixing it with creeping bentgrass, fine fescue or tall fescue. Wash mowers and aerators before moving to other sites so stolon pieces do not spread.

Thatch: Builds thatch fast. Core-aerate every year once the turf is 2 years old, or topdress. Thatch is less of a problem in heavy traffic and shade (University of Wisconsin).

Common supina bluegrass problems

If a pesticide is needed, use only products labeled for that use; the label is the law. If you hire someone to treat a lawn, make sure they hold your state’s pesticide applicator license; see our pesticide applicator license guide. To put a name to a lawn weed, use our weed identification guide.

Questions we get about supina bluegrass

Similar lawn grasses

Tall fescueLolium arundinaceumChewings fescueFestuca rubra subsp. commutataCreeping red fescueFestuca rubra