Smother it

It is already March and if you have not planted your native plant garden you might want to consider putting it off until next year. Once again this rain year is turning out to be rather disappointing, and it does not look like we will be seeing noticeable amounts this spring. Although the numbers are better further north, according to The California Weather Blog, most of the rain fell in two major rainfall events. Not only has it been dry, but it has also been warm. These conditions do not bode well for late planting.Nevertheless, it is not a bad time to attack your lawn. If you are sure that you will be putting in a low water-use garden next year, you can start ridding yourself of the lawn and planning the new garden now. And fortunately, Emily Green’s timely KCET series, After the Lawn, provides important information on how to do this safely and effectively.

In the coming weeks and months KCET will explore how safe lawn conversion can be done around existing trees. The online written series “After the lawn” will address landscape challenges from curb to back fence. If you want to keep lawn, it will tell you how to do it and save water. If you want to go native, we’ll be on it. The theme: How to look at your lot and improve its function and beauty while increasing its water efficiency. Stay tuned. Ah, in the meantime, remember your trees. Here’s a good brochure on tree irrigation from the Inland Urban Forest Council.

I have already discussed one method of lawn reduction, neglect, offering suggestions and discussing its pros and cons. Other Lawn Removal Methods can bring more rapid change; however, whatever method you use, follow Green’s suggestion in After the lawn: Part 1, “Cut your sprinklers by all means but run new irrigation to trees. Keep them healthy.”

Of all of the ways one can lose the lawn, I think smothering is my favorite. Yes, it sounds gruesome but it is really quite gentle. Basically, you cover the lawn with a layer of stuff, usually organic mulch. The mulch blocks the sunlight, reduces air exchange (though coarse mulch should be used to minimize this), and starts to decompose, warming the soil below. Most turf grass withers and dies beneath, though Bermuda grass will be a tough adversary with this and most other methods.

The lasagne method – in which cardboard or newspaper is laid beneath mulch – is a variation of smothering. Some descriptions of this method include mowing the lawn low, then digging it out or rototilling it. The surface is then watered well and covered with cardboard or newspaper, making sure to overlap the pieces for complete coverage. Brown and green organic material are layered on top of the cardboard. Each layer is amply watered to facilitate rapid decomposition. The gardener, then, just waits for nature to take its course.

This method is not without controversy (gardening is part art, part science and a whole lot of argument). If the area is on a slope, the mulch placed on top of the cardboard is likely to slide down, and in windy areas, it may be more likely to blow around. And of course, it is an extra step. If you don’t overlap the cardboard well, grass and weeds will grow between the pieces. This happened to me because I am not a neat and careful person, I’m kind of a mess. The Garden Professors point out that digging or rototilling damages soil structure. Furthermore, the cardboard or newspaper, in addition to being slippery, reduces air exchange at the surface of the soil which can lead to anaerobic processes and the proliferation of disease-causing microorganisms.

I, too, am not a big proponent of this method. For one thing, it is too much trouble, and I am averse to buying anything, except plants. Furthermore, although it may work well for vegetable gardens, the resulting soil is very high in organics, a condition not beneficial to many California native plants. A serious windstorm provided me with first-hand evidence that simply applying a six inch layer of mulch in the form of coarse wood chips is all that is required. This does increase the organic composition of the soil but leaves and wood chips are not nearly as rich in nitrogen as the soft greens of kitchen waste. Furthermore, the coarseness of the material killed the grass while allowing air and water to freely penetrate the soil. And of course, the process more closely mimics what happens in nature when trees succumb.

On November 30, 2011 a major windstorm hit our area. There was severe tree damage throughout the region. Two mature trees in our front yard, an avocado and a deodar, lost a lot of limbs. We called an arborist who removed broken limbs and chipped the smaller branches. All of the debris was kept on site. The following pictures show how easily and thoroughly simple mulching can get rid of lawn.