Cover Story

Solutions for Shady Lawns

By Kenneth Ingram, Institute of Applied Agriculture, UMD

Growing turf in the shade is one of the oldest problems faced by turf managers. Shade is an issue for almost all the turf managers under the umbrella of the Maryland Turf Council. Residential turf managers and golf course superintendents deal with shade problems primarily from trees, while commercial turf and sports turf managers deal with shade caused by buildings and stadiums. Dry shade has been described as “gardening hell.” There are no easy solutions, and often drastic measures are taken such as massive tree removal programs on golf courses or an expensive switch to artificial turf in stadiums. There is a staggering amount of hardwood mulch used in commercial landscapes often as a turfgrass alternative which does not provide the ecosystem services of living plants. This article will focus on residential lawns where those expensive options are not practical.

Americans love their trees. It is an interesting subject with some excellent written works that look at this phenomenon from historical, psychological, and scientific perspectives. The latter being that Maryland is in the Eastern Deciduous Forest biome and the climax vegetation is woody plants. Together with the emphasis on sustainability these days we as turf managers must face the fact that trees are here to stay. But as turf managers we also know that Americans love their lawns. That eastern forest understory is often not desirable for homeowners. It is fairly useless for recreation, blocks views, is often decimated by deer browsing, and ticks are a serious issue anytime plants are more than ankle high. So many turf managers together with homeowners “hold out” for turfgrass in these situations often with marginal results. Traditional management programs for shady turf sites usually included the following:

• Increased mowing heights to maximize the photosynthetic leaf area.

• Canopy and root pruning of trees for increased light.

• Overseeding with shade tolerant turfgrasses, primarily the fine fescues.

• Adjusting irrigation regimes to counter surprisingly droughty conditions from tree root competition.

Perhaps the only new recommendation in the past 30 years, and one not utilized enough in my opinion is the use of the plant growth regulator Primo™ (Trinexapac-ethyl). By regulating plant hormone levels in shaded grass plants thicker turf is often the result.

In years past when the battle for turf in the shade was abandoned alternative groundcover plants were used, often with beautiful results. Bugleweed (Ajuga sp.), Vinca/Periwinkle (Vinca minor), Pachysandra (Pachysandra terminalis), Liriope, (Liriope sp.), English Ivy (Hedera helix), and Wintercreeper (Euonymus fortunei) seemed to be viable solutions. But alas, we learned that these plants are non-native and out of favor now, and in the case of the latter two extremely invasive. There are several native groundcovers for sunny areas but a dearth of shade tolerant native groundcovers. Recently however, there has been an explosion in the number of sedges (Carex spp.) in the marketplace which have “game changing” possibilities for shady lawns.

The genus Carex contains thousands of plants. There is actually a division of botany devoted to the study of sedges called caricology. First of all, for turf managers, these plants are not the dreaded weeds Yellow and Purple Nutsedge (Cyperus spp.) commonly called sedge that are menacing to Maryland turf. Carex sedges do have the “edges” on leaf blades and the threesided stem like the Cypress sedges but similarities end there.

Carex woodii (Wood’s sedge)

Research recently published by Sam Hoadley, Manager of Horticultural Research at the Mt. Cuba Center in Hockessin, DE narrowed the vast number of Carex species to those suitable for the Mid-Atlantic region. Sixty five species were studied and five showed tremendous potential for mowed or unmowed lawn alternatives in the shade. Those species are listed the following table:

Carex woodii (Wood’s sedge)

Shade Mowed Rating – 4.9

Sun Mowed Rating – 4.9

Habit – spreading

Building on its stellar reputation earned in the regular trial, Carex woodii was also a top-rated plant in the mowing evaluation. Performing exceptionally well in both sun and shade, this species developed into dense mats that efficiently covered ground and suppressed weeds.

Carex eburnea (bristle-leaf sedge)

Shade Mowed Rating – 4.6

Sun Mowed Rating – 3.6

Habit – clumping

Carex eburnea has the narrowest foliage of any sedge in the trial and is quite similar in appearance to fine fescue turfgrass. This species forms low-growing clumps that spread very slowly over time. Carex eburnea occurs in rocky soils and outcrops in the wild and could be a great lawn option in dry sites.

Carex socialis (low woodland sedge)

Shade Mowed Rating – 2.4

Sun Mowed Rating – 4.6

Habit – clumping

Carex socialis is a species that was dramatically improved by mowing in this evaluation. Unmowed plants became weak after the first years of the trial, but when mowed, this species bounced back with surprising vigor. In full sun C. socialis developed dense, impenetrable clumps that would be the envy of any turfgrass enthusiast.

Carex pensylvanica (Pennsylvania sedge)

Shade Mowed Rating – 4.3

Sun Mowed Rating – 4.4

Habit – spreading

Carex pensylvanica is a tried-and-true species in the landscape that unsurprisingly was a good candidate for mowed Carex lawns. This species gently covers ground although there are small gaps present in the carpets of foliage that are exploited by opportunistic weeds.

Carex jamesii (James’s sedge)

Shade Mowed Rating – 4.0

Sun Mowed Rating – 4.4

Habit – clumping

The dark-green foliage of this plant is put into direct focus when it is mowed, and individual plants make consistent and orderly clumps. Since Carex jamesii is not rhizomatous and does not have a large footprint when mowed, many closely spaced plants would be needed to work as a lawn substitute.

Sedges require less input than traditional turfgrass species and have the added benefits of being sources of food and habitat for beneficial insects and wildlife. Unmowed sedges have interesting and attractive seedheads as well. For more information refer to the publication Carex for the Mid-Atlantic Region at https://issuu.com/mtcuba/docs/22034-carex_reportfinal121922?fr=sMWI3ZDU2ODU5NjY