Organic Lawn Care

Knowledgebase

Rising concern for the environment has led to more people asking for information regarding organic lawn care. Many people want to decrease or eliminate the use of synthetic fertilizers and pesticides in their home lawns. There is concern that some of these products may be harmful to humans, beneficial insects, wildlife, and pets. With proper knowledge, the homeowner can use naturally occurring resources to maintain a home lawn without using synthetic products. The goal of organic lawn care is to use ecological options, including such concepts as IPM and "least toxic pest management."

Natural organic lawn care differs from conventional methods by allowing the soil to be improved by adding organic matter such as compost (made from plant wastes), certain animal manures (chiefly composted cow, chicken, or horse manures), and other naturally occurring substances. Improved soil contributes to healthy plants that will be less susceptible to damage from pests or environmental stress. Fertilizer may be applied less frequently than in conventional lawn care but timing of applications becomes especially important. Weeds, insects, and diseases are managed by cultural practices that are oriented toward prevention. Natural organic methods also emphasize the recycling of organic wastes.

Natural Organic Lawn Care

The first step in switching from conventional to natural organic lawn care is to evaluate the quality of the existing lawn. If there are few weeds and a desirable grass species, natural organic lawn care can be sufficient. However, if these lawn conditions do not exist it is best to kill the entire lawn and start over. After this decision has been made, the next step is to assess soil quality. A soil test is a fundamental first step to any organic or conventional lawn care program.

Good soil quality is a primary factor in growing healthy grass. Good soil contains adequate organic matter, which improves soil structure by binding mineral soil particles together to form aggregates. This creates greater pore space among the aggregated particles, providing optimal conditions for root growth. Increased pore space improves both soil drainage and water-holding capacity and also improves soil aeration. In addition, sufficient quantities of organic matter in the soil aid in nitrogen fixation, help reduce soil borne plant diseases, and help hold nutrients for plant use. Good soil also contains adequate amounts of the nutrients plants need.

If an existing lawn is to be preserved, the transition to natural organic methods can be instituted at any time. When it is time to fertilize, choose appropriate organic fertilizers to correct deficiencies. Although soil test recommendations are based on the use of synthetic fertilizers, use the nutrient rates recommended in the soil test report as a guideline for the application of natural organic fertilizers.

If an existing lawn is of poor quality and needs to be killed and re-established a non-selective herbicide such as glyphosate (Roundup®) may be considered since it does not leave residues in the soil. Covering the lawn with plastic in the heat of summer can also be used the kill existing grass, though this may be difficult to do if the lawn is too large.

The advantages of starting a new lawn are: (1) improved, disease-resistant grasses can be selected; (2) soil can be amended with organic matter; and (3) nutrient deficiencies can be corrected (per soil test) before seed is sown. Adding organic matter to the soil before seeding is more effective in changing the percentage of organic matter in the soil than top-dressing an existing lawn with compost.

There are two key points to keep in mind when going organic. (1) Compared with conventional lawn care, organic methods take longer to produce visible results in most cases. For example, synthetic fertilizers release nitrogen immediately and therefore produce a rapid "green-up," whereas the response of grass to organic fertilizers may take months to years. (2) Perfection is an unreasonable expectation. Tolerating a few weeds or insects here and there is part of the natural organic approach. When natural organic methods are used consistently over time, a reasonably uniform green lawn that is resistant to adverse environmental conditions and/or pests can be expected.

Nutrient Sources

Organic fertilizer sources of nitrogen include dried blood, vegetable and feather meals, manures, and sludge, and may range from 3-10% by weight. In organic form, most of the nitrogen is bound to complex molecules and is inaccessible to plants until it is slowly released by the natural activity of soil microorganisms. Other organic nitrogen sources include composted manures, cover crops, and green manures. In addition, nutrient availability may be limited during cold periods when activity of microorganisms is minimal. The typical slow response time and high cost associated with the use of organic products has led to an increase in the sales of fertilizers that contain mixtures of natural/synthetic and natural/inorganic nutrient sources. While use of these products reduces green-up time and cost, they are not in compliance with "natural organic" standards.

Cultural Management

Maintenance of a vigorous lawn depends upon cultural practices to increase the diversity and health of beneficial organisms in all levels of the soil. An ecological lawn seed mix should thus be comprised of a variety of grass species and cultivars in order to take advantage of the disease-resistance qualities of each and to reduce susceptibility to damage by pests specific to any one. Endophyte-enhanced grass mixtures are a good choice for sustainable, organic lawn care situations. These grasses tend to be more vigorous than conventional varieties and have resistance to foliar-feeding insects such as chinch bugs, billbugs, and sod webworms.

Integrated Pest Management (IPM)

The IPM strategy for organic lawn care is prevention. The aim is to use plant selection, establishment, and maintenance practices to promote, conserve and enhance natural pest controls. A healthy, well-rooted lawn can compete with many species of weeds. Mowing high is another organic strategy aimed at shading out particularly troublesome annual weeds such as crabgrass, which require light to germinate. In addition, organic lawn care endorses the need for education aimed at acceptance of a certain level of "weeds."

An organic approach to pest management for insects focuses on "least toxic control strategies." Avoidance of broad spectrum pesticides that affect "nontarget" organisms results in the maintenance of natural pests. Biologica controls, such as predators and parasites, can also be used in addition to natural organic sprays and dusts. Also, as mentioned above, endophyte-enhanced grasses are resistant to a number of surface-feeding insects. Certain "insecteating"nematodes parasitize the larvae of sod webworms and cutworms. Bacteria such as Bacillus thuringiensis (sold as B.t.) can be used against the sod webworm and the cutworm, as well. Botanical insecticides such as rotenone and pyrethrum are also allowed as part of an organic pest control program.

Management of Lawn Weeds

Inspect the lawn regularly for weeds and weed seedlings. Weed species tend to be found in certain habitats. For example, crabgrass is a spring annual that needs light to germinate. Therefore, crabgrass seedlings are most likely to be found in thin areas of the lawn in the spring. Mid-summer would be an excellent time to look for mature plants to identify seed sources for the following year while late fall would be the best time to look for seedlings of winter annuals. Dandelions are also common in home lawns, especially where the lawn is thin or mowed too short. One way to eliminate them is to cut as much of the dandelion roots as possible beginning in early spring, immediately after they have leafed out. Continue this as new growth appears. The root will send up new growth until the plant runs out of energy.

As with the rest of organic lawn management, employing sound cultural practices is important to reducing weed problems. A short list of the most important cultural practices follows:

• Mow at 2 ½ – 3 inches to keep the lawn dense and discourage weed seed germination. Frequent mowing will prevent or reduce seed production in some weed species.

• Fertilize more heavily in fall and keep fertility levels up in late spring and summer using slow release products.

• Frequent, shallow irrigation discourages root growth and can encourage weed seed germination.

• Renovate chronically thin lawns and reseed bare spots and thinned areas. Fall is the best time to do this.

Use organic-based herbicides such as corn gluten or herbicidal soaps, as appropriate. Herbicidal soaps are fatty acid-based, non-selective contact herbicides. They work by contact and will not affect underground plant parts. They can be quite effective against small annual and biennial weeds such as common chickweed and crabgrass. Soaps are less effective on perennial grasses and larger tap-rooted weeds. Because herbicidal soaps are non-selective, they can adversely affect desirable plants as well as weeds.

Corn gluten is an effective pre-emergence herbicide that can control crabgrass, barnyardgrass, foxtails, dandelion, lambsquarter, pigweed, purslane, and smartweed. The proteins in corn gluten act on germinating seeds to inhibit root growth. After application and a period of water stress weed seedlings wilt and die. Corn gluten also contains 10% nitrogen by weight, and has a slowrelease fertilizing effect when applied to home lawns. If applied at the rate of 20 pounds per 1,000 square feet this also effectively applies 2 pounds ofactual nitrogen.

The best time to apply corn gluten is shortly after the last spring frost and again in the fall. Water following the application if there is no rain and then allow the area to dry for two or three days. A dry period following application is required for corn gluten to effectively kill emerging weed seedlings. If excessive rain occurs following application then reapplication may be necessary. A corn gluten application can inhibit grass seed germination, so avoid using this product if reseeding or overseeding an area of the lawn.

Factors to consider in the use of corn gluten include: (1) expense; (2) knowledge of the weeds and their life cycles because it must be applied in a four- to six-week period prior to weed seed germination; and (3) possibly inconsistent results because excessive moisture and microbial soil activity can reduce its effectiveness.

Management of Lawn Diseases

Disease management focuses on providing optimal conditions to maintain the health of both grass and soil. Good drainage and proper soil pH contribute to the conservation of organisms antagonistic to pathogens. Practices such as planting disease-resistant grasses, increasing air circulation, and avoiding watering at times when the grass will remain wet may all be used in attempts to prevent disease.

Disease-causing organisms are always present in the lawn, ready to infect weakened plants when environmental conditions become favorable. Environmental conditions that are not optimal for growing grass and that stress the lawn provide the conditions for lawn diseases to develop. These include too much or too little water, excessive heat, shade, and poor soils. Very succulent grass growing under a high maintenance fertilizer program will often provide conditions favorable for plant pathogen growth and infection.

Most common lawn diseases seldom kill the grass but cause aesthetic changes that most homeowners dislike. Fortunately, most lawns recover with changes in environmental conditions and proper maintenance. There are currently no natural organic fungicides that are useful in lawn disease management. The first line of defense against lawn diseases is the establishment of proper soil conditions before grass seed is planted to

help to ensure a healthy lawn. The second line of defense is the proper choice of grass species, cultivars, and quality seed. The third line of defense is proper lawn maintenance practices that can reduce disease problems, such as mowing, irrigation, fertilizing, and core aeration.

For severe lawn disease problems due to poor soil conditions or excessive thatch, renovation may be the best solution. Disease problems related to poor grass selection can usually be corrected by renovation with disease-resistant varieties.

Management for Lawn Insects

Healthy lawns contain a variety of insects, yet most people don't know one insect from another and consider them all bad. Very few insects actually injure home lawns. Many organisms in a lawn may prey on or parasitize potential pests, while others help in decaying organic matter in the lawn. For example, ground and rove beetles readily attack lawn caterpillars as well as the eggs of sod webworms and white grubs. A number of tiny flies and wasps also parasitize lawn pests.

The most important practices to reduce insect pests in lawns are proper grass species and cultivar selection, thatch management, proper mowing, and irrigation.

Adapted from: University of Massachusetts Extension, 1999; Ohio State University Extension

Where to Obtain Organic Lawn Care Products

Local garden centers may or may not carry organic lawn care products, but they are available from the following online and catalog sources (not an exhaustive list):

Gardens Alive!

Offers corn gluten, organic fertilizers, and grass seed mixtures (including those with endophytes)

(513) 354-1482

http://www.gardensalive.com/Default.asp?bhcd2=1204236080

Gardener's Supply

Offers corn gluten, biological pest controls, composting equipment

1-888-883-1412

http://www.gardeners.com/

Extremely Green Gardening Co.

Offers fertilizers, corn gluten, nematodes, grass seed

http://extremelygreen.com/

Planet Natural