Mulch for California native plant success

I'm a believer in what Southern California landscapers (even the ones that like agapanthus) have known for many years - mulch applied over the top of the soil keeps all the plants happier. This may be even more important for California native plants than for exotics.

For many years I cleaned up my leaf litter like most of my neighbors and threw it away - all that potential, gone. Us urbanites had somehow got the notion that flower beds and the like had to be completely clear of leaves to be orderly. I got a bit smarter later on: I composted the leaf litter. That was better, but I mostly ended up digging it into my heavy soil - as a top dressing, fully composted greens (and browns) don't really stand up to the rigors of sun, wind, and rain. I use it mostly on my vegetable garden now. There's some that claim that partially rotted leaves are a great top dressing, but I have yet to generate enough partially rotted leaves to make a difference. They're either overflowing my compost bin and there's no signs of rot or more often I've turned a summer's worth of lawn trimmings from my neighbor, the leaves from his tree and mine, and my own lawn trimmings into about 10 gallons of compost - there's a lot of fluff in vegetable matter.

On top of the soil I now apply various different kinds of wood mulch, which is not dug in. This is important - digging in your mulch causes it to decompose, which consumes nitrogen from the soil. The nitrogen is ultimately released, of course - mass balance has to be true in the end. But while the mulch is decomposing that nitrogen isn't available to your plants. People that dig uncomposted leaves or sawdust into their garden must supplement with nitrogen. Of course, already mulched greens don't have this problem.

Wood mulches placed on top of the soil decompose slowly so nitrogen depletion isn't an issue. What the mulch does do is prevent weeds by shading them out, keep the soil moist and cool, and provide safe harbor for beneficial bugs. It also makes it easy to pull weeds, since they are usually not deeply rooted. In my vegetable garden I started with shredded cedar compost - it seemed to make a more tightly bound mat, but I'm now using redwood bark.

My native plants all get the bark too. And the leaves? I don't worry about them so much any more.

Today I found a local bulk supplier of bark mulch - B.D. White Top Soil, Inc at 192 S. Prairie Ave in Torrance (weekdays, 7:30 to 4:00). They scooped me up a cubic yard of top quality bark mulch for $56.29 with tax. A cubic yard is what fits in one scoop of the smaller of their two skip loaders and fills the back of my Ford Ranger. This price is a bit better than the home improvement centers charge, and the product seems superior.


  1. Mark and I used to rake the fall leaves into the furrow between tomato beds in the vegetable garden. Then we uprooted the skeletal vegetable plants and tossed them in. Finally, we tossed a light layer of dirt on top.

    In the spring, after the danger of snow and frost passed, we had composted leaves. I don't know if that was the "right" way to do it, but the leaves had decomposed.

  2. I forgot to mention this was when we lived in Boulder, Colorado.

  3. Areas with winter seasons seem to get away with that sort of composting. Here, it's too dry to compost like that unless you add lots of water. I could add water to my compost bin twice weekly and it would be about enough. Exposed leaves on otherwise dry ground can last a long time in California.

    I wouldn't have thrown the plants back in for fear of promoting some special tomato plant pathogen, but that's just my paranoia. Sounds like you had the ticket to healthy soil.