Ecologically Sound Lawn Care for the Pacific Northwest

This a summary of a report (provided courtesy of David McDonald, Seattle Public Utilities) which aims to provide three tools for persons interested in best environmental practices in lawn care:

1. An introduction to the concept of ecologically based lawn care, and a review of the scientific literature that supports a change from traditional chemical-intensive practices;

2. Practical recommendations for ecologically sound lawn care in the region west of the Cascade mountains, assembled from interviews with turf scientists and professionals and a review of literature;

3. An annotated bibliography that reviews source documents useful to residents, landscape professionals, and public resource managers.

Lawn Care:  An Ecosystem Approach

Like forests or prairie grasslands, lawns are dynamic ecosystems: communities of plants, soil, and microbes; insects and earthworms and the birds that feed on them; and humans who mow, water, fertilize, and play on the lawn. The interactions of all these community members shape the dynamic equilibrium we see as a lawn. Understanding and working within the natural processes that shape the lawn and its soil community can yield a durable, beautiful lawn that is easier to care for. As it turns out, these ecologically sound methods will also help reduce water use, waste generation, and water pollution. 

Why Make A Change?

The ecological approach to lawn care described in this report has several advantages, including:

• Reduced mowing time and fertilizer needs, and improved turf color, quality, and density.

• Enhanced resistance to diseases and weed invasion.

• Improved nutrient availability, and less soil compaction, acidification, and thatch buildup.

It is also useful to understand the disadvantages of some common current lawn care practices:

Water use: Lawn and garden watering in the Lake Oswego area increase water use by 30% during the summer. Endangered Species Act listings of salmon will increase the cost of new water supplies.

Solid and hazardous waste generation: Grass clippings from lawns are overloading regional composting facilities, when they could be reducing fertilizer use by 25-50% if left on the lawn, thus potentially reducing water pollution.

Current pesticide use in the region: The EPA estimates that 1.1 million pounds of pesticides are applied in urban areas of this region each year, with 213,000 pounds being applied by private households, predominantly on lawns and gardens. Many residents say they use “weed and feed” (a pesticide/fertilizer mix) on their lawns.

Fertilizer and pesticide pollution, and effects on aquatic life: Much of the phosphorus that enters Oswego Lake, canals, and creeks comes from single-home residential areas. Sources include fertilizers and soil wash-off. Excess nutrients promote algae blooms that decompose and deplete the oxygen needed by fish and other aquatic life.

Side effects of pesticides and soluble synthetic fertilizers on the turfgrass ecosystem: A number of studies demonstrate that regular use of these products, especially at higher levels, can reduce the diversity of essential soil life, such as earthworms, and contribute to soil compaction and acidification, and increased thatch build-up in lawns.

Possible human health effects of pesticides: While not conclusive, a number of epidemiological studies have reported an increased incidence of cancer and other health problems among families that use common lawn and garden pesticides. Children may be particularly susceptible.

Healthy Lawns Grow on Healthy Soil: 
Cultural Practices that Support the Turf Grass Ecosystem

Current best practices for lawn care west of the Cascade mountains, drawn from interviews with turf professionals and an extensive review of the scientific and professional literature include:

• Setting realistic expectations for lawn appearance, and tolerating a few weeds.

• Proper site selection, and preparation of the soil by tilling in compost to a depth of 6 to 12 inches.

• The selection of site-adapted and disease-resistant grasses.

• Moderate fertilization with natural or natural/synthetic-slow-release combination fertilizers, to build soil nutrient reserves and biodiversity.

• Mulch-mowing (also called “grass cycling”) whenever possible.

• Mowing regularly (remove only 1/3 of grass height each time), and mowing a little higher, at 2 to 2^-1/₂ inches on most lawns (or 1 inch for bentgrass lawns).

• Avoiding over-watering: water deeply, to moisten the whole root zone, but infrequently, to limit disease and build deeper roots; and water dormant lawns at least once a month during the dry season to improve post-drought recovery.

• Renovation/improvement practices that include aeration, compost topdressing, and overseeding, to reduce compaction, increase water infiltration, improve soil structure and natural disease control, and crowd out weeds.

• An integrated approach to pest problems (weeds, insects, and diseases) that includes:

1)      Correctly identifying the cause of the problem;

2)      Understanding the biology of the pest organism and its natural predators;

3)      Setting realistic thresholds of acceptable damage to the lawn from pests;

4)      Monitoring for pest problems at appropriate times of the year; and

5)      Treatment of over-threshold problems with methods that support the turf grass ecosystem and have the fewest non-target impacts on beneficial soil organisms, wildlife, pets, or humans.  Repeated broadcast or calendar-based applications of pesticides should be avoided because they may damage the diversity and stability of the grass/soil ecosystem.

In Conclusion:  Towards Sustainable Lawn Care

Turf professionals reported a number of barriers to widespread adoption of the recommended practices, including: customers’ lack of tolerance for some weeds in lawns; the desire for a deep blue-green lawn color, which can only be maintained by overfertilization; the erroneous belief that grass cycling contributes to thatch build-up in lawns; the promotional power of the chemical industry; lack of knowledge about alternatives; and the demand for immediate results on a limited budget.

Lawns are a meeting point for many public concerns, including water use, disposal of mountains of clippings and containers of hazardous chemicals, water and air pollution, human health effects, effects on salmon, birds and other wildlife, and the desire for attractive green spaces to play and live in. This offers a challenge and an opportunity for groups of resource agencies, citizens, and landscape professionals to come together and develop a consensus for change.

This entire report can be downloaded off the internet at   http://www.ci.seattle.wa.us/util/rescons