By JOAN S. BOLTON
South Coast Beacon

It may start innocently enough. A fan-shaped mound appears on the edge of your lawn. Then another. And another.

Before you know it, what seems like a ravenous horde of underground demons has wreaked havoc throughout your garden, creating a maze of mounds of freshly pulverized earth. Below ground, these beasts are chomping on roots, undermining prized plants and causing erosion with their extensive tunnels.

The culprits? Most likely a new generation of pocket gophers.

These destructive, tunneling rodents dig and chew their way from one end of the South Coast to the other every year. They mate between January and April. By June, they’ve been bearing their young and there’s a whole new round of mounding and munching going on.

It’s interesting to note that gophers are solitary critters that share their burrows only during mating and caring for their newborn offspring.

Why so many mounds then? The varmints are incredibly industrious: a single gopher may dig up to 600 feet of tunnels and build 70 mounds a month. Multiply that by several gophers, and you have a real problem.

What’s a gardener to do?

Defending your garden starts with creating barriers.

Pocket gophers rarely venture above ground. Instead, they eat what’s already buried in the soil or yank whole plants into their tunnels.

You can protect individual plants or bulbs by planting them within pre-made gopher cages. Or build your own from aviary wire. Half-inch or quarter-inch mesh is available from hardware stores in 4-foot-wide rolls. Fold over the edges to prevent sharp points from sticking out of the ground. Mulch the area with bark as an extra precaution.

For vegetables, build raised beds, then line the sides and bottoms before you fill them with soil. Be sure the aviary wire is deep enough. If it’s not at least 12 to 18 inches below the eventual soil line, you might rip through it when you turn over the soil for a new crop.

Or, depending on the size of your garden, you can establish an underground wall around the perimeter. I know one avid gardener who dug 2-foot-deep trenches at his fence line, then pounded in plastic panels that are usually used to direct tree roots deep into the soil.

But aviary wire only goes so far in protecting your plants. It doesn’t get rid of the gophers and does nothing for existing plants. And the verdict is still out on the plastic in the trench.

Trapping is the next tactic.

My favorite device is “The Blackhole Gopher Trap,” a 4-inch-wide piece of black PVC pipe bearing a spring-loaded loop crusher at one end and a dime-sized hole at the other end. It’s easy to use and safe around children and pets.

Look for a fresh, fan-shaped mound. Dig out the soil in the center. Poke around with a sturdy wire, weeder or screwdriver to find the tunnel. Use a shovel to make a clean slice at the tunnel’s mouth: this is what you will press the Blackhole against. But first, set the spring and sprinkle some dirt inside the Blackhole. Then shove it against the tunnel, making sure it’s parallel to the ground. Leave the dime-sized hole at the other end uncovered.

Gophers don’t like light, and will constantly work to plug openings to their burrows. In the case of the Blackhole, the gopher scurries out to plug the light, trips the spring-loaded mechanism, and Wham! the loop slams into the gopher’s chest. It can’t breath. It dies.

When you see that the trap has sprung, lift it out. If the gopher has only filled it with dirt, shake it out and re-set it. If you’ve caught the gopher, press the spring to release it. There’s no blood, no mess. The dead gopher is intact and easy to dispose of.

Macabee traps are a more traditional method. They’re also more gruesome: prongs spear the beast.

For the macabees, you’ll need to locate the main run — rather than one of the many little “kick-out” tunnels.

Main runs generally link two mounds. Use a long piece of metal, such as a curtain rod or rebar, to probe the ground, about one foot away from a fresh mound.

Dig out the tunnel and set two macabee traps, facing opposite directions. Leave enough room between the two to drop a handful of carrot tops or other fresh, green material. Gophers have a keen sense of smell and will want to investigate. By the same token, wear gloves while setting the traps, to hide your human scent.

Attach the traps to a stake to prevent a snared gopher or scavenging dogs or coyotes from moving them.

Cover the hole with a board, making sure no light can enter. Otherwise the gopher will push dirt ahead of himself to repair the hole and that dirt will trigger the trap, rather than the gopher.

Bait is an alternative. But it carries a risk of poisoning other animals. Predators, such as hawks or even neighborhood cats, that eat poisoned gophers can fall victim to secondary poisoning.

Other techniques include gassers or compression bombs. These work best in moist soil, which helps to confine the gasses to the tunnels. If the ground is dry, the gas may dissipate through cracks in the soil and lose its effectiveness.

Old-timers may swear by attaching a hose to their car exhaust and directing the flow into a hole. But with California’s strict emission standards, newer model cars don’t produce much carbon monoxide.

You can also try flooding out your gophers. But be warned: you may use a vast amount of water and the gophers are not likely to drown quietly deep within the earth. Instead, the water will inevitably flush them out. And then you’ll have live gophers scurrying about.

Joan S. Bolton is a free-lance writer and garden designer who lives in Goleta. She can be contacted at www.santabarbaragardens.com.