KENNEWICK -- Whether your lawn is pampered or neglected, weed-free or overcome with weeds, fall is the most important time of the year to give it the attention it deserves.

Recovery

Summer heat stresses the cool season turf grasses in our lawns. As the weather cools in early fall, lawns start to recover. You can help that recovery along with properly timed fertilizer applications. An early September (Labor Day) plus a late October (Halloween) or early November application are recommended for our region.

You still need to irrigate your lawn, but as the weather cools you should be cutting back on the amount of water being applied. If you're watering every day, you may only need to water every second or third day. By watering every day when the lawn doesn't need it, you're wasting water, washing away needed nutrients and encouraging the growth of weeds.

Weed management

One of the best ways to manage lawn weeds is to encourage a healthy turf with properly timed fertilizer applications and irrigation. However, weeds still find their way into lawns, and October is the best time to apply herbicides for the control of broadleaf weeds. That's because many of the perennial broadleaf weeds in our lawns, such as dandelions and plantain, are actively growing during the cool fall weather. Herbicides applied when they're actively growing are more effective.

There are also winter annual broadleaf weeds, such as chickweed, that germinate in the fall and grow during late fall and early spring. These are more easily controlled in the fall when the plants are young and small. Efforts made in the fall to encourage a dense, healthy turf can also help control summer annual weeds such as crabgrass, purslane and pigweed that will germinate in the spring. A dense turf makes it more difficult for weeds to germinate and grow.

Also, fall is a good time to apply herbicides to your lawn because landscape plants are not actively growing and not as susceptible to damage from the herbicides.

Which herbicides?

There are a number of broadleaf weed control products on the market.

Most broadleaf lawn weeds can be controlled with a combination of 2,4 D, MCPP and dicamba.

However, products containing dicamba should not be used in the root zone of desirable trees and shrubs because they can cause damage. This includes trees and shrubs growing in the lawn area or along the lawn border. Even if trees and shrubs are in a landscape bed, they're still vulnerable if their roots are growing into the lawn area.

Keep in mind that the absorbing roots of a tree can stretch to areas as far from a tree as the tree is tall and beyond. If you have vulnerable plants with roots throughout the lawn, it would be advisable to simply spot-treat weeds or use a product that doesn't contain dicamba.

There are also certain lawn weeds that are particularly difficult to control, including bindweed, black medic (Japanese clover), clover, creeping wood sorrel (oxalis), ground ivy, henbit, mallow, prostrate spurge and violet. Better control of these can be achieved with lawn herbicide products containing triclopyr.

Before purchasing any herbicide product for your lawn, identify the weeds you're trying to kill. WSU Master Gardeners can help you identify your weeds. Just dig them up and place them separately in zipper-locked plastic bags. Bring them to the Extension office in the Benton County Annex at 5600-E W. Canal Drive, Kennewick. Of course, read and follow all label directions and precautions on the herbicide product you select.

To contact the Extension office, call 735-3551.

* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension Office.