Mulching Basics

When used correctly, mulch serves many important functions in the landscape.  With so many options available, it can be difficult to figure out what kind to use, how much, where to use it.  Below are suggestions for mulching in a California native plant garden.

What is mulch?

Mulch is any material spread over an outdoor surface to cover soil. Mulch is used to help retain soil moisture, suppress weeds, and improve the look of your garden. There are two types of mulch, organic and inorganic. Organic mulches are those that will break down over time because they are based on natural materials such as tree bark, leaves, and pine needles. Inorganic mulches are petrochemical based products such as plastic sheeting or rubber chips. Consider using organic mulches in almost all situations!

Why use mulch?

Mulch reduces soil water losses, suppresses weeds, and protects against temperature extremes, especially in places where it snows.  Mulch also feeds soil biology as it decomposes, helping to create healthy, living soil.  Healthy soil means healthy plants!

What type of mulch?

Different California native plants prefer different types of mulch.  For example, some plants may require decomposed granite or gravel and rocks as mulch, while others will die if mulched with rock.  Know what mulch plants prefer by visiting Calscape.org.  Finally, avoid large, bark type mulch or big wood chips.  Since these big pieces take a long time to decompose, and they end up depriving the soil and plants of nutrients.

How much mulch?

Mulch well with a 2-3” layer.  Be sure not to pile mulch against the trunks or stems of plants as it will rot them.  Apply mulch in late spring and early fall.

As the plants mature, they will start providing their own mulch in the form of fallen leaves, flower parts, and other plant litter.  It is best to leave the leaves and other plant litter in place!  This is beneficial to the plant as it promotes the natural cycling of nutrients, and also provides habitat for beneficial insects, birds, and other species.

Leave a few areas MULCH FREE!

Many native bees are ground burrowers.

When planning your garden, identify patches of bare ground to remain mulch free to allow space for ground dwelling bees and other beneficial insects that need open soil.

Remember!

• If you sheet mulched during turf removal, mulch is already in place at planting time.
• Skip the petrochemicals, and don’t use plastics or weed cloths as sheeting under the mulch. They will kill the beneficial biology in the soil, and prevent the natural nutrient cycling that plants depend on for nutrients.