Canadians Against Pesticides
ORGANIC LAWN CARE
* Adapted from materials produced by Heather Apple of the Canadian Organic Growers, Durham Chapter
It is possible to have a healthy attractive lawn using only organic methods. The key is to provide the ideal conditions so that grass grows vigorously and crowds out any weeds, and is also healthy and resistant to diseases and pests. Proper mowing and watering promotes healthy grass without risking the environment.
Lawns should be mowed to a height of approximately 7 centimetres (3 inches) - never shorter than 4 cm (1.5 in). This will result in a good growth which keeps the grass vigorous, shades out weed seedlings and helps conserve soil moisture. Cut your lawn regularly - never removing more than the top 1/3 of the total grass blade in one cutting.
Make sure your blade is sharp, as a dull blade tears the grass and makes it susceptible to disease. Mulching blades cut grass multiple times producing very short clippings full of necessary nutrients. Mulching blades are handy for grinding or mulching fall leaves for storage and feeding to composters throughout the year. Mulching blade retrofit kits, adaptable to a variety of power mowers, are available at your local hardware or gardening centre (install yourself or seek help from a dealership). "Scalping", or cutting the lawn very close, is very harmful to the lawn. When too much of the leaf is cut away, the plant can begin to starve because you may have cut into the crown of the grass blade located at or near the ground surface. Grass blades grow from the crown, which is why you can cut off the tips without harming the plants. Also, small top growth cannot support the large healthy root system necessary to seek out water and nutrients.
After mowing, leave the grass clippings on the lawn. They will decompose, adding organic matter to the soil and recycling such nutrients as nitrogen, potassium and phosphorus found within them. When the growth is too thick or long and the amount of clippings is excessive, collect them and add in 15-cm (6-in) layers to backyard composters to help break down other yard and food waste. Fresh grass clippings are "greens" and provide nitrogen; dried grass clippings are "browns" and provide carbon, both of which are required for successful composting. Grass clippings are also useful around trees, shrubs and vegetables as garden mulch as they help enrich and moisten the soil.
Lack of watering harms the grass and the micro-organisms in the soil, driving earthworms down to greater depths. It also gives an advantage to certain weeds that can withstand drought conditions better than grass. Your lawn only needs 2-3 cm (1 in) every three to seven days depending on slope drainage, soil types, root zone depth (length of roots) and weather conditions. Adjust watering accordingly. Do the "catch can test" to measure your correct watering level. Place a few identical-sized cans on your lawn. Turn your sprinkler on and time how long it takes to fill the cans to your lawn's desired level (set sprinkler timer accordingly).
Shallow watering only encourages small, shallow root systems, resulting in a dry layer of soil between the moist surface and the deeper levels. Water deeply, but don't over-water your lawn.
Practice water efficiency and water during off peak hours (11:00 p.m. - 8:00 a.m.) to save stress on Toronto's water supply system. If you choose to water while you sleep, make sure to use an accurate timing device to guard against over watering, which can lead to fungus and rot problems. Watering in the very early morning allows time for the sunlight to dry out the grass blades.
Seed bare or sparse spots in your lawn to prevent weeds from taking over. Mid-August to mid-September is a good time to seed because the ground is still moist and warm, yet weed growth is slow, and there's enough time for grass plants to develop good roots before the weather turns very cold (spring seeding encourages problematic weeds that can smother new grass plants). Rake the area of dead grass and debris, sprinkle on some compost and rake in a bit.
Inexpensive seed mixtures often contain inappropriate grasses. Consult with your garden centre about an appropriate mix for your conditions. Seed generously - 15 to 20 seeds per 6.45 cm2 (sq in) - then rake the seeded area lightly. Never let newly seeded spots dry out until the grass is well established. Even then they will require extra watering for some time.
Thick, luxurious grass shades out newly germinated weed seedlings and eventually crowds out established weeds. If you have a manageable weed situation to begin with, this crowding out will occur gradually over a couple of years. It can be speeded along by digging out dandelions and other deep-rooted weeds with a long, sharp knife or other tool, and by hand-pulling other weeds.
Diseases and Pests:
Diseases are generally caused by poor soil drainage, improper watering and mowing, acidic soil, inappropriate grass varieties, feeding with chemical fertilizers, and neglecting trace minerals.
If you consistently have problems with poor grass growth, weeds, diseases or pests, it would be a good idea to take a soil test. Your soil may have a nutritional deficiency which can be corrected by adding a natural fertilizer. It could also be that your pH is off. Dolomitic limestone raises the pH (makes the soil more alkaline). Gypsum (calcium sulphate) and peat moss lower the pH (make the soil more acidic). If all else fails, there are exciting alternatives to having a lawn - doing your entire property in "edible" landscaping, using ground covers, planting a wildflower meadow or planting native species.