A relatively new product making the rounds in organic lawn-care circles is corn gluten meal, a by-product of the milling process for corn. It controls weeds that germinate in the fall, such as black medick, stinkweed and shepherd's purse, by inhibiting seed germination. The only caution is that if you are overseeding your lawn in late summer or early fall, you shouldn't use corn gluten meal for at least four to six weeks after you've spread the seed. If you're not seeding, it can be used any time until Halloween. Think of it as an organic trick for a lawn treat.
The gentle approach
The three autumn tasks listed below are essential to maintaining a healthy, organic lawn.
Aerating gets oxygen into the soil, helps prevent or reduce thatch and lessens compaction. There are several different aeration tools; which one you use will depend on the size of your lawn. For large areas (say, an acre or more), consider renting a power aerator that lifts cores of soil from the turf. For smaller lawns, a core cultivator (a hand tool) will do the job, as will a pitchfork or forked spade. You'll need to drive the tool into the soil 10 to 15 centimetres deep, wiggle it around, then pull it out. Whichever method you choose, don't worry about the cores dotting the lawn—simply break them up with a rake.
Top dressing is a good idea after aerating; compost is the top dressing of choice for the organic lawn. Using sifted compost, rake in enough so that you've added a layer about one centimetre thick over the entire lawn surface. For large areas, you can use a fertilizer spreader to distribute the compost. Within days, it will settle into the soil.
Fertilizing is done in early to mid-fall to promote deeper root growth and is good preparation for the winter ahead. It's important to use a fertilizer low in nitrogen so that grass plants don't have an above-ground growth spurt. There are a number of organic lawn fertilizers on the market. Be sure to follow the manufacturer's directions—too much of a good thing is bad; for instance, you could overfeed the grass just before winter, leading to tender growth. As well, excess fertilizer can run into the sewer system.
Pam Charbonneau, a turfgrass specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs, suggests a non-destructive way to look for leatherjackets and other grubs under the grass: use a sharp knife to cut three sides of a 30-centimetre square, 7.5 centimetres deep. Then, simply fold back the turf and have a look. The grass mat can be folded back into place, with no permanent damage.