Roger Cook
Photo: Keller & Keller
"I don't know why people don't do more yard work in September," says This Old House landscape contractor Roger Cook. "Fall is the absolute best time to get things done, and it gives you a head start on spring." For most of the country, autumn's moderate temperatures and plentiful rainfall offer the year's best gardening conditions. What's more, many plants are in a phase of intense root growth, which makes fall a great time to plant, transplant, and feed them. So when the first hint of cool air sweeps through your yard — from late August to early October, depending on your latitude and altitude—here's what you can do to dress up your landscape and lay the groundwork for a lush lawn and beautiful flower beds come spring.

"To grow a lawn that greens up naturally each spring and that resists drought and disease, you need to foster a strong root system," says Roger. This requires annual maintenance — best done in the fall when weeds aren't likely to sprout.

AERATE: Constant trampling by people, pets, and lawn mowers compacts the soil beneath lawns and prevents air, moisture, and nutrients from penetrating to the roots. If water puddles on top of the turf after a rain, it's time to aerate. For a small lawn, use a garden fork to punch holes in the soil every few inches. To treat a larger area, rent a walk-behind aerator at your local garden center. (You can save money by splitting the rental costs with a neighbor.) These gas-powered machines have hollow teeth mounted underneath that pierce the turf and pull up small plugs of earth as they roll along. To protect sprinkler heads, be sure to mark and avoid them. Afterward, use a flat shovel to flick a light coating of a sand-and-compost mix over the turf; it will settle into the holes and help improve drainage further.

FEED: After the weekly mowings necessitated by summer"s speedy growing cycle, fall's slower growth rates can be a relief. But there"s still lots of activity going on underground. "Grass roots keep on growing until the ground gets down to around 40 degrees," says Roger, "so this is a good time to nourish them." Use a spreader to apply fertilizer to the lawn, once at the beginning of the fall season and again just before the first frost. Roger prefers a high-phosphorus mix, like 12-25-12 (the three numbers denote, in order, the ratio of nitrogen, phosphorus, and potassium in the fertilizer). This mix stimulates root growth rather than greenery.

SEED: Planting new areas, reseeding bare patches, and overseeding sparse ones now gives the grass a chance to establish itself without having to compete with weeds, which tend to germinate in the spring. Roger suggests not buying the cheapest grass seed at the nursery. Instead, look for one that contains less than 0.5 percent weed seed and comprises a mix of several different grass types and named varieties (e.g., "Alene" Kentucky bluegrass or "Wizard" perennial ryegrass). "That way, if disease affects one, you"ll still have a good-looking lawn," he says. Also, check the label to see that the seed was harvested no earlier than the previous year. Before sowing, loosen the soil to a depth of 4 to 6 inches with a small tiller or spade and add a lime fertilizer. Then, after seeding, scratch the planting area with a rake to ensure that the seed will come into contact with earth. Water daily.
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