How to Mulch
Summer mulches for annual flowers and vegetable gardens are normally applied in midspring, once the soil has warmed enough for active root growth. For best weed suppression in a perennial border, apply mulch in early spring, before the forsythia blooms. For best results, remove any existing weeds before applying mulch. Mulches applied for winter protection should be laid down in early winter, once the soil has cooled but before it has frozen.
For trees and shrubs, spread mulch evenly to a depth of 2 to 3 inches. For trees and shrubs in beds, mulch the entire bed. For those in a lawn, mulch a wide ring (extending from 3 to 6 feet out from the trunk) around each plant. Never pile mulch against tree trunks. Pull mulch back away from the trunk about an inch or so. As organic mulches decompose, they may need to be replenished somewhat every year; but don't let mulch build up to depths greater than about 4 inches.
For flower beds, mulch can be applied up to 3 inches deep (after settling), but should be kept pulled back slightly from plant stems. Mulches should thoroughly cover an area to a uniform depth to be most effective. Low or bare spots are prone to weed problems.