Mulching Do's and Don'ts

Newly mulched garden bed

A newly mulched bed with freshly cut bed edges makes a landscape look neat and well tended.

Mulch is more than "just the icing on the cake" to make your garden look nice. When used correctly, mulch can reduce weed growth, moderate soil temperature, and slow the evaporation of water. Here’s a few things to remember before you get spreading this spring:


  • Use an edging tool to cut a sharp edge around garden beds before mulching. This prevents lawn grass from creeping into garden beds while making a neat edge that looks nicely tended. Cut a “lip” of two or three inches around the edge so that it catches mulch that might roll down the bed and fall into the adjoining lawn or sidewalk.
  • Use Preen Mulch with Extended Control Weed Preventer for added weed protection. Preen Mulch has an added weed preventer in it so it blocks weeds from germinating for six months. Each bag covers up to 12 square feet since it only needs to be applied to a depth of 2-inches to suppress weed growth, instead of the usual 3-inch depth recommended for other mulches. Available for purchase at Lowe’s.
  • Leave space between the base of the plant and the mulch. Always keep mulch at least a few inches back away from the crown of all plants to allow for air movement. When mulching around trees and shrubs, don’t pack it against the trunks and stems, where the moisture and wood-decaying organisms in most mulches can rot bark.
  • Pay extra attention around the base of trees and shrubs. A layer three to four inches deep should be plenty. Layers should not be deeper than where the base of the trunk begins to flare into the root system. Mulch can kill whole trees if it’s packed in excess quantities against a tree’s trunk – a practice known as “volcano mulching”.
  • Water after applying mulch. Smooth the mulch, then soak the beds to settle it in.
Mulch around tree.

Mulch around tree


  • Expect all mulch to stop weeds. Weeds are tough to beat. Invariably weed seeds find their way back into the garden, carried in by wind and birds, and oftentimes mulch serves as a handy growth medium. Prevent weeds from sprouting by sprinkling a layer of Preen Garden Weed Preventer on top of mulched beds. Be sure to water after applying.
  • Layer mulch too deep. Too deep a layer prevents essential oxygen from reaching the soil, causing root suffocation. For perennials, 2-inches is enough and around annuals and veggies, 1-inch.
  • Add fresh mulch on top of old mulch without loosening it up first. Fresh mulch can go on top of old mulch, but loosen the existing layer first if it’s matted down or crusted to improve drainage and air movement. If you already have enough mulch in place, no need to add more; if the plants are suffocated remove some of it.

Mulch can be applied either before or after soil preparation of new beds. Some pros prefer to mulch the entire bed free of plants ahead of time, and then make holes for the plantings, being sure to pull away excess mulch from the crowns. Others prefer to plant first and then mulch around them.

Preen Garden Weed Preventer

Applying Preen Garden Weed Preventer.

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