Austen Thibault, The Union Democrat

Rattlesnakes, bears or unexpected weather may worry summer hikers tromping through the Mother Lode's backcountry. But they should add to that list clandestine marijuana growers, according to law enforcement officials.

The months between now and October are high season for illegal marijuana grows - found at all elevations and typically on public lands or isolated private property.

Never safe to stumble into, they are becoming even more prolific and dangerous, according to law enforcement.

According to Craig Davis, commander of the Tuolumne Narcotics Unit, which recently conducted some raids on forest lands, most grows nowadays are operated by drug cartels based in Mexico.

They are almost always tended by guards, and those guards are increasingly carrying high-powered firearms.

An AK-47 assault rifle with a 30-round magazine was found at a grow site in Tuolumne County last week. Firearms have also been confiscated from grow sites in Calaveras County.

"Hunters, fishermen and hikers might head to some of the same places these growers set up," Davis said. "If you come across one, the best thing to do is just back away. Mark the spot, if possible, in your mind or with a GPS device."

Signs of a nearby grow site include hoses running from creeks and streams, small isolated campsites, wilderness areas that look manually cleared, and the jagged-edged, odd-numbered leaves of marijuana plants.

Grow operations have been found all throughout the region, Davis said, from the lowest foothill elevations up to about 10,000 feet.

The plants must be somewhat near a water source, but are usually placed somewhere not too likely to be wandered onto.

In Calaveras County, more grow operations are found on large tracts of private property, usually without permission from the property owner, according to Sgt. Chris Hewitt of the Calaveras County Sheriff's Office.

There are more attractive grow areas on private estates in Calaveras County, and there's less public land in the county in general than Tuolumne County, he explained.

A grow site being on private property makes it no less dangerous.

In 2007, growers shot at a father and son hunting on property near Sheep Ranch. The two escaped alive and later led authorities to 3,000 plants.

"If anyone suspects a grow on their property, do not under any circumstances try to confront them yourselves. Call the Sheriff's Office," Hewitt advised.

In Calaveras County, authorities have conducted several raids this season, resulting in three arrests of undocumented immigrants, three guns found and 46,174 plants eradicated, Hewitt said.

One gun was a handgun and the other two were rifles.

One immigrant was deported and the other two are slated to be.

In Tuolumne County, no arrests have yet been made this season. However, about 24,000 plants have been eradicated and an assault rifle was found - the first assault rifle to be found in a Tuolumne County marijuana grow bust to Davis' knowledge.