This Weeks Turf Happenings: Seedheads, Hawkweed, & Mosquito Spray

Kevin W. Frank
Assoc. Professor & Extension Turf Specialist

Seedheads Surging in Turf

The cool season turfgrasses growing in Michigan have been in full-blown seed head production mode in the last week.  The common lawn grasses, Kentucky bluegrass, perennial ryegrass, and tall fescue all produce seedheads as do some grassy weeds like annual bluegrass (Poa annua).  Seedhead production requires energy from the plant so it is likely the turf will not only look stemmy due to the seed stalks but the turfgrass may even thin out.  Consider a fertilizer application following the seedhead flush to help the turf recover, especially if you haven’t fertilized yet this spring or fertilized back in April. Keep the mower blade sharp and don't lower the mowing height to try and remove seedheads.  Annual bluegrass produces seedheads below the 1/8 inch mowing height on golf course putting greens so lowering the mowing height is not going to solve the seedhead problem.  For those that think the lawn is going to be reseeded by the natural seedhead production, think again.  Even if the seed was allowed to reach maturity which would take about 4 months, allowed to dry, and then harvested, you’d still need to make sure that seed would find a home in the soil in order to germinate.  If you need to fill in some areas in your lawn it’ll be easier and more effective to go buy some seed. 

Seedheads in a Kentucky bluegrass lawn.

Kentucky bluegrass cultivars differ in seedhead production.

Yellow and Orange Hawkweed Flowering in Turf

One of the most consistent weed flowering events every year is yellow and orange hawkweed on Memorial Day weekend.  Somehow despite all the differences in spring weather we experience from year to year, hawkweed always seems to bloom on Memorial Day weekend.  Yellow hawkweed may look like dandelion to the untrained turfgrass eye but there are some differences.  Probably the most obvious difference between dandelion and yellow hawkweed is in the flower.  Although there are still some dandelions flowering out there, generally dandelion flowers earlier and also it only produces one flower per stalk.  In contrast, yellow hawkweed produces several flowers per stalk and appears in patches instead of as a single plant due to it’s creeping nature with stolons and rhizomes. This may facilitate the mowing around hawkweed patches that I often see, it’d be tough to mow around each individual dandelion plant.  Yellow and orange hawkweed are a little easier to tell the difference, hint..think color.  Hawkweed’s presence is often an indication of poor growing conditions and is often found near roadsides, in boulevards, or in country lawns that are rarely fertilized.  Although common broadleaf herbicides will be effective in control if you don’t improve the growing conditions it’s likely to be back. 

Yellow hawkweed with multiple flowers per stem.

Mosquito Spray Reminder on Turf

The start of this summer appears to be another fantastic year for mosquitos in Michigan. When you’re applying your favorite mosquito repellant to your legs, don’t apply it while standing on the turf.   Every year I see examples of mosquito spray killing turf on golf courses, usually next to the first tee but sometimes in the middle of the fairway.  Mosquito repellant usually isn’t going to kill the entire plant but will definitely kill the leaf tissue and leave some interesting crime scene like outlines of the perpetrator. 

Good reminder for golfers on mosquito spray damage.