STEP 1: Weed Prevention
As with most types of prevention, discouraging weed seeds from sprouting requires some extra time now so you can save a lot of time later. When weeds have already taken hold in a section of your yard, remove them before planting. Pull them by hand if possible, or use an herbicide such as glyphosate (Roundup), and apply it with caution. This nonselective chemical will kill almost all plants. As always, carefully read directions before using.
Install landscape fabric.
Synthetic landscape fabrics provide a physical barrier to weeds yet allow air, water and nutrients through to plant roots. Spread the fabric over bare soil around trees and shrubs; overlap several inches of fabric at the seams. Anchor the material with U-shaped metal pins, then conceal it with 1 to 2 in. of mulch, such as stone or bark chips.
You can also use landscape fabrics to control weeds under decks and in pathways (spread over the excavated soil base before you add gravel or sand). A 3x50-ft. roll of landscape fabric, such as the Typar shown below, costs about $10. The fabric is also available in 36-in. die-cut circles (about $3 each) for installing at the base of trees.
Smother with mulch.
Left unattended, weeds will quickly fill in unplanted areas and any open ground around plants. Mulch spread over the soil surface blocks the sunlight most annual weeds need to take hold. Weeds that do sprout are easy to pull because soil beneath mulch remains loose and moist. Coarse chipped or shredded bark is a good choice for large areas between trees and shrubs because it decomposes slowly and doesn't easily blow away. For paths, a thick layer of sawdust provides good weed suppression because it depletes nitrogen in the soil.
After clearing a landscaped area of visible weeds, put down coarse-textured mulch up to 4 in. deep. Apply a fine-textured mulch that packs tightly, such as shredded leaves, to a depth no greater than 2 to 3 in. Keep the mulch a few inches away from the trunks and stems of plants to prevent disease problems.
Apply preemergence herbicides.
Preemergence herbicides, such as those containing oryzalin or trifluralin (look on the label for these chemicals), or nontoxic corn gluten meal, kill weeds just as they germinate and will not eradicate established weeds. For a preemergence herbicide to be effective, you must apply it to soil cleared of visible weeds; also, you have to water most of these herbicides into the soil.
Check the label to determine if it is safe for use around the kinds of landscape plants you have and effective against the weeds normally present.
Deprive weeds of water.
Weeds can't survive without moisture. In areas with little or no summer rain, drip irrigation or soaker hoses help prevent weed seeds from sprouting by depriving them of water. These systems deliver water to the root zone of plants at the soil level. The soil surface and area surrounding the plants stays relatively dry. In contrast, overhead sprinkler systems spray water over the entire soil surface and supply both garden plants and weeds with water.
You can get in-depth information on drip irrigation from Michigan State University and the Irrigation and Green Industry Network in the "Where to Find It" section .
