Gardening Word of the Day: Mulching

What is mulch?

Mulch is plant/animal material, usually waste from tree clippings, animal poo, leaves, green waste, bark, or other “outside” organic materials that have been gathered and processed through a chipper, a composting process, or just heaped up in a pile and “seasoned”. If it has been composted, it will contain microorganisms that are good for your garden; the digestive system for plants. If it hasn’t composted much, or it’s too full of nitrogen (such as fresh chicken poo or cow manure), it may burn your plants. Some horse piles, usually layered with hay, will burst into flames when the nitrogen gets too hot!


Mulching your trees and flower beds is the single most important thing you can do to ensure a healthy garden and maximum results. But don’t put the mulch right up against the bark of a tree! If the tree’s roots are all underground, then putting mulch against the trunk may cause phytophthora (a fungal disease organism) to grow and set up the eventual demise of the tree.

I tell all my clients to put a “monster truck tire” sized ring of mulch around their trees.

Benefits of mulching:

1. Reduces the need for water: you water less because there is less evaporation when the water seeps into the mulch and is held there.

2. It feeds the plants and trees: Fertilizer can only be taken up by the roots when the soil is rich with life. The bacteria, fungi, worms, and other critters that feed on organic matter and live symbiotically with the plants’ roots are the ones who make the fertilizer bio available so that it can be taken up by the plant.

3. It looks good. Have you ever seen dry, cracked soil? Not too pretty. Cover that up!

4. Mulch suppresses weeds. It’s harder for weed seeds to germinate when they are too far under a 2 inch (or thicker) cover of mulch.

5. It improves the quality of your soil. If you’ve ever been told to “amend your soil” it is always about adding organic matter. Mulch, being made of organic matter, when mixed with your soil, allows for proper aeration, improves the fertility and tilth (read: structure and suitability) of the soil, and enriches it with each application. You should be mulching every six months, in a perfect world. Adding your own composted kitchen scraps around your plants would be ideal.

6. Mulch protects the soil. Sun and wind will erode your soil and reduce the soil level. Often, tree roots will become visible. The mulch acts as a replacement for the soil, covering those roots and preventing further erosion.

Where to find mulch in the South Bay. Here are five types of mulch and the benefits/pitfalls of each:


1. Gaffey Street Mulch isn’t actually on Gaffey Street; it’s on the access road across from the San Pedro DMV and running alongside the San Pedro Community Garden. It is just North of the recycling and hazardous waste center. The pile is usually available on Saturday mornings and gone by the afternoon. They sometimes drop it off during the week as well. It comes from the City’s composting facilities, which takes the green waste from your cans, chips it, piles it up and seasons it, mixes it. You will find it in varying degrees of breakdown. Sometimes the chips are large, sometimes it is really fine. But you will always find pieces of glass, trash, and debris among the material. It’s not that bad, but if you have small children or barefooted people walking through your garden, don’t get this mulch. Plus, you have to shovel it into containers or a truck because it’s self-serve.

2. Go online and sign up to receive chips from tree companies. You will need to have a driveway large enough to take a huge dumptruckload and you might not be home when it happens. They want the flexibility to come anytime and leave you a “present” in your driveway. They also might come with chips that contain evergreen tree material, which is highly suppressive to growth. Great for making paths and keeping out weeds, but not great for growing fruit trees.

Not free

3. Hy Grade at 25200 Vermont Ave., Harbor City, CA 90710. 310-326-6996 Henry Alvarez sells “planting mix” or “compost” for $25/cubic yard. He has a “scoop” which holds the equivalent of one cubic yard, so the good news is that you don’t have to shovel it into your truck by yourself and it takes very little time to get a truckload. The downside is, the material is not “hot” and as such, it does not contain much biological activity. The stuff he calls “compost” is not made out of the type of material that percolates well. Water will pool or run off of it, not percolate through it evenly. But it is very fine, and it looks quite good. When mixed with your bio-active soil, it provides organic material for the little buggers, so if you already have a thriving garden, it makes a nice topcoat.

4. Kellogg’s Amend, Planting Mix, bags of compost, mulch, bark, etc. at Home Depot, Lowes, Armstrong, etc. You can buy bags of almost any organic material to use as mulch. If you have a small garden, or you just can’t see yourself dealing with trucks and gardeners, this is the way to go. If the bag is still hot, it may still contain microorganisms, and that is a good thing.

5. Mini bark from BD White, 18800 South Broadway, Gardena, CA 90248. 424-285-4129 For top of the line material, you can’t do better than mini bark. It costs $65/cubic yard, and BD White will deliver for an extra fee. They will dump 10 cubic yards, but they will not spread it. This stuff is beautiful, but the most excellent thing about it is that it contains mycorrhizae and bacterial populations that the others might not have. And it will never have termites in it, like the aforementioned wood chips, because it’s from the bark of trees, not the part that would contain termites.

For a dumptruck company, call Garnica Trucking (310) 780-1289; ask for Steve. His truck will hold up to 10 cubic yards. A cubic yard is 27 cubic feet, and the typical bag of material from the garden store contains only 2 to 3 cubic feet.

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