What is Mulch?

Straw mulch on collards and onions

Mulch in a community garden--wood chips on the paths, straw in the vegetable beds

Wood chip mulch on perennial and native plants

What's mulch? Why mulch?

I mentioned in my last post that soil microorganisms like to stay moist, and since these organisms increase soil fertility, it is useful to keep them happy. Mulching is an easy and cheap way to achieve this result.

Mulch is any soil covering. It is most often an organic matter of some kind--wood chips, oat or rice straw, pine needles, partially decomposed compost--these are all common, free or cheap materials great for mulching. Other mulches that cost money are cocoa hulls, coconut fibers, commercial wood chip mulch, or black plastic sheeting (often used to cover strawberries commercially). Another free mulch material is dry leaves, although it's not as good as some other choices since the leaves can mat, and prevent air circulation to the soil and plants. Some tree leaves may be alleliopathic which means they create conditions that most plants won't tolerate.

In my opinion, no one should spend big money on mulch. Nature provides many excellent materials for free--wood chips can be attained free from a tree trimmer, pine needles can be gathered from under a pine tree, and oat or rice straw (very useful in vegetable gardens) can be purchased for a small fee at horse feed lots or the race track. Sometimes Halloween or Christmas Tree lots give away bales of hay or straw for free when they are done for the season.

The benefits of mulch are many--keeps the soil and thus the plants moist, increases nutrient fertility by benefiting soil microorganisms, lessens the amount of watering needed, keeps weeds down, insulates plants from both very cold and very hot conditions, and loosens soil which makes weed pulling and digging easier. Here in Northern California, where we have a xeric moisture regime (no rain for 5 months out of the year), mulching makes a lot of sense.

Heavy mulches like wood chips, cocoa hulls, and pine needles are good for perennial plants, trees, shrubs, and paths. Straw is best for mulching annual vegetables.

If you want a vegetable garden, and the spot in your yard you have in mind is covered with weeds, the best way to prepare it is to sheet mulch the spot. More about sheet mulching next time.