The homegrown crowd is also getting more ingenious than ever. Check out the contraption above, seized in Washington State. Last year, Chad Robert Latham got 15 years in prison for designing and operating these "Ferris Wheel" growers that, in all, rotated over a thousand pot plants. Each machine, fashioned from aluminum, held 24 rows of plants–eight to a row. The plants cycled under grow lights and were sprayed at the top or drenched at the bottom with a hydroponic nutrient solution.

Here's another striking setup, found last month in underground chambers on remote land in Santa Ysabel, a mountain town east of San Diego:

Inside a garage, authorities uncovered a hidden closet elevator which opened to a four-foot-wide, 65-foot-long tunnel. The tunnel, in turn, led to underground rooms crammed with 454 pot plants along with "irrigation, lighting, electrical and ventilation systems," according to the DEA. You can find more photos here.

Then there's this operation in Manhattan (below), announced April 9 by the DEA, in which agents seized over 700 plants from a vacant apartment on the city's Amsterdam Avenue. The growers pirated electricity, water and natural gas to fuel a complex with separate rooms for growing, drying, packaging and processing, timers for lighting and heat, commercial-grade air conditioning, and sophisticated pumping systems.

Much of the indoor pot is being grown in California, where the number of indoor plants grabbed by authorities has quadrupled in the past three years. Just last month, cops in Los Angeles seized six houses filled with the stuff. In one three-bedroom home, every room was used for growing weed except the bathroom and kitchen.

But that pales compared with what's been going on in northern Georgia. Over the past two months, police have seized more than 70 indoor pot farms– almost 10 times the amount they found last year. One ring, linked to dealers in Miami, is tied to at least 17 houses, most of them apparently bought exclusively to grow pot in.

The prevalence of homegrown pot has even helped inspire a TV show: Weeds. The Showtime cable series stars Mary-Louise Parker as a widowed mom in California, who grows and sells marijuana from suburban houses to support her family.

Nationwide, the amount of homegrown pot being seized still accounts for less than a tenth of that found outdoors, largely on farms and national forest land. Nor does it take into account the huge amounts smuggled in from Canada and Mexico. But authorities say the trend toward indoor pot is clear. "Law enforcement is becoming a lot more savvy," says Garrison Courtney, a DEA spokesman. "Outdoor seizures reflect better enforcement and newer technology. The drug dealers are smart–they know we're catching on, so they're moving it inside."

Photo credits: U.S. Drug Enforcement Administration