October 2009


Cardboarding Pasadena Backyard (c) 2009 Orchid Black

Cardboarding Pasadena Backyard © 2008 Orchid Black

Using recycled cardboard to kill your Bermuda lawn, called as sheet mulching, is the easiest and most environmentally friendly way to do it.  Unlike St. Augustine or Marathon, which can both be removed with a sod cutter on a large site, or with minimal digging on a small site, Bermuda can’t be easily removed by digging.

Digging can remove it, but it’s not an easy weekend project without 10 friends and a 10 ton low-boy construction debris dumpster.  Then you either dig down about a foot, and throw away all the grass and dirt to that depth (why the low-boy is needed), or dig down about a foot, and sift each shovel-full through half-inch hardware cloth to remove the runners, which means ultimately lifting each shovel load at least twice.  Until recently, the only alternative to the dig-out or the dig-and-sift methods has been to use glyphosate (Roundup), which, while safer than some herbicides, is not benign.

A few years ago, I was introduced to the idea of sheet mulching.  It sounded simple: just smother the lawn in a layer of cardboard and mulch, wait a couple of months, then plant into it.  I thought it would work for everything except Bermuda.  I kept that thought until I had young environmental activist clients who wouldn’t use glyphosate, didn’t have the finances to hire a crew for several days, and, because the wife was pregnant, weren’t able to do that kind of labor themselves in their very large yard.

I suggested sheet mulching, since their options were limited.  They gathered appliance-store and bike-store boxes, and laid them across the yard, making sure there were no openings between boxes that could admit light, and spread mulch over the whole thing.  Three months later, I visited the site, and surprise!, there was almost no bermuda left.  The few single pieces left were stringy, weak, and easy to remove.  Most of the cardboard had degraded under the mulch, and the small cardboard pieces that were left were easy to pull out and throw away.

Cardboard is an excellent light barrier, and I think of it as “mulch pressed into a shape.”  It biodegrades, improving the soil as it does so.  Adding a layer of at least two inches of shredded mulch on top improves the light barrier which keeps the grass from photosynthesizing.  The Bermuda travels under the cardboard, exhausting its underground resources and is unable to replenish them.  This is why the process takes time.  While the best time to do it is in summer, it can be done at any time.

While wet newspaper or sheets can work as the first layer, I have gotten the best results from cardboard, which is a better physical barrier.  Since it is covered with mulch, it looks like a finished landscape and won’t upset the neighbors.  While some references suggest using compost under the cardboard to help kill the grass more quickly, compost shouldn’t be used where natives will be planted as they don’t like the high fertility.

Though people love the idea of using black plastic to kill the lawn, it doesn’t work well here.  It may work in places where the ground retains water and there is a lot of heat in summer.   In those places, the water in the ground cooks the plants under the plastic.  Unfortunately, in California the ground is drier.  Because plastic isn’t as good a light barrier, the grass can often still get enough light to keep growing.  Multiple cuts and tears quickly appear in the plastic, compromising the barrier effect.  In the end, cardboard is better.

So, step by step, the first step is to measure the area’s square footage.  Gather at least that much cardboard, plus at least 20%.  The best cardboard comes from appliance stores and bike stores, since it is thick.  Grocery or liquor store boxes may need to be laid in two layers.  Step two is to lay out the cardboard, lapping the edges over each other by at least 2”, with no gaps.  Cover every gap with another piece of cardboard.  When there is a sidewalk or patio, it is best if the cardboard can be laid up over the hard surface and taped down for safety.  If the cardboard can’t be laid over the sidewalk, dig at least 6” down, removing as many of the roots as possible.  Any roots left in the ground at an edge will be an ongoing problem. Step three is to cover with at least 2” of mulch.  The easiest mulch to get is shredded arborist’s waste, which is shredded mixed tree and bark, with some leaves.  See the resources page for sources.  Then, turn off the water to the area, and leave the whole thing alone for two to three months.

Bringing Cardboard over an Edge (c) 2008 Orchid Black

Cardboard at an Edge © 2008 Orchid Black

It is easier to cardboard a whole lawn than to only do part of it, since at the edge, a trench has to be dug out at least 6 to 9” deep, and a physical barrier added where the Bermuda will stop. If the lawn area to remain won’t be very big, it might be worthwhile just to remove the whole thing and replant the lawn areas with St. Augustine, than to deal endlessly with Bermuda runners.

Cardboard and Mulch on Planting Day (c) 2008 Orchid Black

Cardboard and Mulch on Planting Day © 2008 Orchid Black

When time comes to plant, if the cardboard remains, holes can be cut into it with a box knife and plants can be planted through the cardboard.

If you are planning to plant natives this year, it isn’t too late to cardboard, but it would have to be done as soon as possible, with a plan to plant in January or February.

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Epilobium canum and Trichostema (c) 2004 Orchid Black

Epilobium canum and Trichostema © 2004 Orchid Black

California fuchsia (Epilobium canum and others) is one of the star bloomers of this time of year, accenting the landscape with bursts of color in fiery red and orange, which contrasts beautifully with olive or silvery foliage.  Hummingbirds dive close to the ground for its nectar right now.  California fuchsias are mostly drought-tolerant and love sun, unlike their cousin and namesake, the garden Fuchsia, though it is in the same Evening Primrose family.

It is an important nectar source for hummingbirds at this time of year, and bridges the gap for hummers between the sage (Salvia sp.) in summer and the blooms of currants (Ribes sp.) and manzanitas (Arctostaphylos sp.) which start flowering in December.

California fuchsia has suffered from the botanical “lumpers.” It used to have its own name, Zauschneria, which was hard to learn but fun to say.  But the “lumpers” have lumped it in with Epilobium, otherwise known as fireweed, a plant which is horticulturally very different, growing in moist meadows instead of on dry slopes.

California fuchsias range from low mat-forming plants to shrubby perennials up to five feet high, though most are two to three feet high by about the same wide.  Many spread by rhizomes underground, making them a good choice for filling in slopes between deep-rooted California shrubs.  California fuchsia can look best spilling over rocks, as I have seen in the local mountains.

East of California, Epilobium canum ssp. latifolium is sometimes called Fire Chalice, which stirs the imagination in a way that California ( not really a) fuchsia doesn’t.  I’ve wondered why few of the variety names attached to California fuchsia have much romance.  There are Lipstick dahlias and daylilies, and Firecracker penstemon, but there is no Firecracker California fuchsia, or Scarlet Lipstick California fuchsia.  It’s almost as if horticulturists don’t want to let people know how brightly colored it is.

E. canum (c) 2005 Orchid Black

E. canum © 2005 Orchid Black

Varieties are mostly named by place, such as Select Mattole, Uvas Canyon, and Catalina, and by foliage color, like Silver Select and Wayne’s Silver.  Most love sun, but a few, such as Catalina, and varieties from Northern California, tolerate light shade.

Most of the fuchsias are almost fully deciduous, leaving brown stems with brown leaves attached after their fall bloom.  Because of this they are best used only as an accent.  November and December is a good time to cut the stems close to the ground, after harvesting the fluffy seedheads to share or to prevent seeding.  Some experts say to “mow it,” to emphasize how much they should be cut back.  The plant will bounce back with new stems the following year.

Some lower-growing forms such as Select Mattole and Everett’s Choice don’t need to be cut back to look good.  The lowest-growing form that I know is Select Mattole.  Coming from Northern California, it needs more water than others.  Very old plants may get brown in the center, but otherwise, both varieties form a neat low mat year-round.  Low varieties, though a good choice for a parkway because of their lack of height, they are brittle and could break from foot traffic in a heavily traveled area.  Care should also be taken when planting them, as major stems can easily break.

As planting season is almost here, planting some California fuchsias this year will bring color and hummers to the garden this time next year.