Garden tasks for September
by Mary Robson, Area Extension Agent, WSU Cooperative Extension
September's one of the finest gardening months in the maritime Pacific Northwest. Warm air and warm soil make working outside delightful, and days remain light until late in the month.
Lawns need help in September. Fertilize now. Use a 3-1-2 ratio fertilizer, applying it at the rate of one pound of actual nitrogen per 1000 square feet. Water well after fertilizing if rains haven't returned. Continue regular mowing during all the fall months.
Dig out or spot treat perennial weeds with an herbicide. Don't apply a fertilizer product with weed killer in it: WSU turf specialists don't recommend these. A feed/weed type product contains weed killers that will damage any plant "dicot" leaves--this means dandelions, yes, but it also means trees and shrubs that may send their roots under the lawn. These products result in applying pesticides where weeds may not exist, and the clippings from the lawn cannot be used as mulch because of potential damage to broad leaf plants. Lawn grasses are "monocot" and aren't affected by the chemicals that kill weeds such as dandelions and clover. If the lawn is severely infested with weeds, it may be necessary to renovate it now.
Lawn renovation--ah, there's a subject. September, particularly after the middle of the month, is an ideal time to repair or install a new lawn. If there's been some rain, this is a good time to thatch the lawn and aerate it. Both these processes improve lawn growth.
Thatching, done with a manual rake or power machine (these are available as rentals), removes matted grass roots and stolons at the crown level. This thatch, if it builds up, prevents water from reaching the roots and reduces grass vigor. If the lawn feels spongy, and if a plug of turf shows more than about 1-inch build up, thatching is necessary. The raking gets in and pulls out excess dead material.
Aeration, which removes small cores of turf, improves water penetration. After thatching and aeration, bare spots (or sometimes the entire lawn) may need to be over-seeded with new grass. Grass seed mixtures containing perennial rye and turf-type fine fescues do well here. Beware of bluegrasses: If they are a major component of the lawn seed, the grass will not thrive in Western Washington. Do not seed lawns unless there's been rain or it's possible to keep the area irrigated. Lawn seed won't grow if it dries out.
If vegetable crops are harvested, and no fall crops are planted, get a cover crop planted. Crimson clover is a good one--this plant will smother weeds and provides soil fertility. Waiting too long to plant a cover crop doesn't work--the seeds must germinate in the warm days of September. Cover crops grow through winter and are dug into the ground in early spring, before they go to flower, and before the garden is planted again. They break down and improve soil texture and fertility.
Cover crops are a great idea if there's bare ground where a landscape will be planted later. Don't leave bare ground--it's an invitation to weeds. Shelter it with the cover crop, a deep mulch of organic matter (about 4 inches), or even leaves as they fall. Pile them on the ground and dig them in before planting. Bare ground exposed in winter also can wash away with rains.
Slugs, sad to say, breed during late summer and early fall. Keep up evening slug patrols. If applying slug bait, put it out in protected containers such as margarine tubs. Cut a hole in the tub for slugs to climb through, add the slug bait, and replace the lid. Slug baits are toxic to animals (including dogs, cats, and children).
One common slug bait package carries a warning label stating that it's attractive to dogs, and that dogs should be confined during the application to prevent them from believing they are being fed. This warning alone justifies caution in using slug baits, and indicates the wisdom of putting it in a closed container. Read all pesticide labels carefully. Use a magnifying glass if necessary.
Later in the month, transplant evergreens. Don't transplant any deciduous trees until they have finished dropping their leaves. Start a compost pile with leaves, if your garden doesn't already have one. For more information on composting, send a self-addressed stamped (32 cents) envelope (SASE) to King County Cooperative Extension; 506 Second Avenue, Room 612; Seattle, WA 98104. Ask for Fact Sheet #12 on "Composting."
Harvest fruit as it ripens, not allowing it to stay too long on the tree. Clean up any fallen fruit to prevent attracting yellowjackets, fruit flies, and rodents of all kinds. Don't compost fallen fruit: Possums can become real nuisances as they rummage for snacks.
Select spring-blooming bulbs (tulips, narcissus, hyacinth, and crocus, as well as others). Decide where to plant them. Mid-October is planting time.
Add new perennials to the garden, and divide overgrown spring-blooming perennials. Keep annual flowers deadheaded and fertilized to continue their flowering.
Bring house plants back into their indoor homes before Oct. 1. Check them for visiting pests and wash them off thoroughly before returning them to the house. Look under the drain holes for slugs, millipedes, and earwigs. If plants are severely infested with scale or mealybugs, consider discarding the plant rather than contaminating the rest of the house plant collection.
Visit WSU's Agriculture Site on the World-Wide Web at http://www.cahe.wsu.edu.