Lawns and the Environment

from  VNPS Communications

Best Management Practices for Lawn Care

Important decisions about how to maintain a lawn area have received a lot of press as ideas  change about the ways we use, and treat, this part of the landscape. Rod Simmons spoke on the subject recently, and has kindly agreed to share answers to some of the follow-up questions from his presentation at the symposium;  *“Habitat Conservation Forum: Practices that Sustain Virginia’s Wildlife and Native Plant Communities.” People will be at different  places along the spectrum for a variety of reasons, but this post contains valuable insights for all.”

Conservation starts at home, says Rod, first and foremost with:

1. the importance of not using fertilizers and pesticides
2.  the many benefits of keeping some areas natural and not planting and mulching every square inch of ground

The “Freedom Lawn” I referred to stems in part from Redesigning the American Lawn, by three biologists from Yale University; Herbert Bormann, Diana Balmori, and Gordon Geballe.

I say “in part” because the “lawns” and savannah-like glades I briefly presented at the symposium require very little maintenance as opposed to fertilized and chemically treated traditional lawns, but in contrast are refugia for specialized, mostly native vegetation, including mosses and lichens, and wildlife that require such conditions (see photos below).  In short, they are high quality, semi-natural areas vs. the mostly artificial, weedy lawns featured in Redesigning the American Lawn (reducing or eliminating fossil fuel usage notwithstanding).  Moreover, the native “lawns” offer the appropriate native species and habitat for pollinators.

Most of these native “lawns” occur in oak (and oak-hickory) overstory savannahs and glades – places where the forest understory was removed long ago and maintained as such but were not farmed; hence the native soils, soil micro-organisms, and seedbank for diminutive native grasses and wildflowers are retained.  This is a common feature throughout Maryland, D.C., and Virginia.

Old-age Acidic Oak-Hickory Forest grove on south-facing, gravelly colluvial slope at Barcroft Apartments, Arlington County, VA. Pignut Hickory (Carya glabra), Sweet Pignut Hickory (Carya ovalis), and Mockernut Hickory (Carya tomentosa) are all co-dominant canopy trees of the grove. Poverty Oatgrass (Danthonia spicata), woodland carices (Carex spp.), and a host of diminutive wildflowers comprise the “no-mow,” low maintenance, chemical-free turf. Photo by R.H. Simmons.

Negative effects of traditional lawn establishment and maintenance:

Fertilizers, lime, and pesticides destroy most native grasses, wildflowers, and wildlife, including eventually, the canopy oaks.  Apart from golf courses and athletic fields, they are not necessary and should never be used.  This also includes leaf compost and manure – both of which are only appropriate for agriculture, gardens, and traditional lawns, and will disrupt and eventually destroy the balanced, acidic soils, soil micro-organisms, and flora of woodlands, as well as foster the growth of non-native invasive plants.  Nutrient-loading feeds pathogens that destroy trees and native biodiversity!

• Natural woodland glades and “lawns” should never be over-seeded by commercial grass seed mixes or wildflower seed mixes.
  
• No tilling or soil amendments are recommended – soil disturbance is the main cause of non-native invasive species.

Some ideas for establishing or supplementing native lawns:

• Shade (even moderate shade) from canopy trees greatly limits the growth of most turf grass species, most of which are light-demanding.  The many species and varieties of Red Fescue (Festuca rubra) are an exception and will grow and persist in shade.  However, all commercially available species and strains of Red Fescue are not native.
  
• If removing existing turf grass in shade is the goal, consider hand-pulling or shallowly digging out robust clumps or sections of grass and periodically and carefully applying iron sulfate (never aluminum sulfate) or elemental sulfur (Garden Sulfur) evenly over the grass according to the manufacturer’s recommendations.  This will gently acidify the soil and further restrict the growth of turf grass, while favoring mosses and other woodland plants.
  
• Don’t remove the oak leaves and organic matter (twigs, bark, etc.) in fall, but shred them up with the lawn mower and leave in place.  (This will require a few passes with the mower to get the leaves to a small enough size.)
  
• Many of the species native to grassy areas listed below are not readily available as seed from nurseries.  An alternate source for many of them is responsibly collecting seed material from clean meadowy areas locally, and supplemented by pots or plugs from specialized native plant nurseries or rescued material.
  
• Carefully pull or dig non-native weeds.

When one finds open, grassy areas dominated by the species below, it typically indicates a healthy, diverse, and sustainable community.  Species diversity is typically greater on mafic soils of the Triassic Basin in the Piedmont vs. acidic, sandy-gravelly soils of the Fall Zone and Coastal Plain.

Some characteristic native species of oak overstory savannahs and glades are:

Grasses:

Poverty Oatgrass (Danthonia spicata) – dominant and widespread; forms a continuous turf with lots of room for other plants.

Autumn Bentgrass (Agrostis perennans)

Panic Grass (Dichanthelium acuminatum vars.); also Dichanthelium depauperatum, D. dichotomum var. dichotomu D. dichotomum m, and other low Dichanthelia –
not Deer-Tongue Grass (Dichanthelium clandestinum).

Three-awn Grass (Aristida spp.) – mainly in sunny, open areas on mineral soil.
Poverty Grass (Sporobolus vaginiflorus var. vaginiflorus) – mainly in sunny, open areas on mineral soil.

Sedges:

Parasol Sedge (Carex umbellata), Black-edged Sedge (Carex nigromarginata), Reflexed Sedge (Carex retroflexa var. retroflexa), Shaved Sedge (Carex tonsa), and many other low, woodland carices.

Rushes:

Path Rush (Juncus tenuis)

Common Bluets (Houstonia caerulea), Poverty Oatgrass (Danthonia spicata), mosses, and woodland litter and duff in open “lawn” along the Mount Ida escarpment in the City of Alexandria, VA. Photo by R.H. Simmons.

Wildflowers:

Eastern Yellow Stargrass (Hypoxis hirsuta)

Trailing Bush-clover (Lespedeza procumbens); also Creeping Bush-clover (Lespedeza repens) – both prefer some sun.

Pussytoes (Antennaria spp.) – need some sun to bloom well, otherwise it’ll remain non-flowering.

Dwarf-dandelion (Krigia virginica) – in sunny, open areas on mineral soil.

Pinweeds (Lechea spp.) – need some sun to bloom well.

Nailworts (Paronychia canadensis and P. fastigiata)

Pineweed (Hypericum gentianoides) – in sunny, open areas on mineral soil.

St. Andrew’s Cross (Hypericum hypericoides ssp.) – Spp. hypericoides is rare in the greater D.C. area.

Wild Basil (Clinopodium vulgare)

American Pennyroyal (Hedeoma pulegioides)

Lyre-leaf Sage (Salvia lyrata)

Hyssop Skullcap (Scutellaria integrifolia)

Southern Yellow Wood-sorrel (Oxalis dillenii)

Blue Toadflax (Nuttallanthus canadensis) – needs some sun to bloom well, otherwise it’ll remain non-flowering.

Virginia Plantain (Plantago virginica)

Dwarf Cinquefoil (Potentilla canadensis) – dominant and spreading.

Common Buttonweed (Diodia teres) – in sunny, open areas on mineral soil.

Common Bluets (Houstonia caerulea)

Field Pansy (Viola bicolor) – in sunny, open areas; also other Viola spp.

Healthy, low maintenance glade of upland oaks and Poverty Oatgrass (Danthonia spicata), woodland sedges (Carex spp.), and diminutive wildflowers on the flat, gravel terrace at Arlington Forest Park, Arlington County, VA. Photo by R.H. Simmons.

Rod also passed along, in conjunction:
“A few essential aspects of White Oak biology” (as well as other upland oaks)
Richard Murray, Arborist and Tree Biology Notebook author

White Oak trees don’t readily display problems.  By the time they are visible these problems are often too far along to correct.  The state of the oaks reflects our changing global patterns.  Multiple factors are involved, none of which are coincidental.

1. They are obligatory species for mycorrhizae (composite organ of nonwoody roots).  The fungal component and the organ itself are sensitive and easily disturbed.

2. The non-woody roots of White Oaks are concentrated in the upper soil horizon and tend to spread laterally and form thick mats.

3. The tree depends on the degradation of annual leaf layers and the diversity of other organic soil components (living, dying, and dead).  Soil damage from events such as logging or urban construction (including gardening) can trigger serious problems for White Oaks and other obligatory species.  This is one reason that White Oak, Hickory, Beech, and other obligatory species don’t fare well as street trees.

4. Forest trees tend to be tall and less wide than open grown trees.  In urban areas many trees were cleared leaving remnant forest White Oaks, allowing them to grow large and broad.  Larger trees have a larger energy budget for metabolic processes, including defense.  When stressed by disturbances, energy reserves are diminished.

5. White Oaks tolerate drought, but not constant wetness.  The cultural practices of removing leaves, planting grass, and using fertilizer salts and irrigation reduce mycorrhizae and the biological diversity of soil.  Larger trees with a now smaller root system and a compromised energy budget set the stage for root rot.  These trees, in turn, become more prone to uprooting. 
 
Preserving and increasing the size of natural areas will aid trees and the organisms they support.  Planting trees in clusters or allowing nature to reclaim open spaces with pioneer species will help retain the diversity of species and of aging stages.  Street trees can be planted in rotation cycles.

Rod Simmons

*Symposium partners: Habitat Partners© Program of the VA Department of Game and Inland Fisheries and the Coastal Zone Management Program, based at the VA Department of Environmental Quality