As plastic bottles shuttle along humming conveyor belts in General Hydroponics' vast Sebastopol factory, a row of nozzles fills the bottles with a bright pink liquid.
The production of this proprietary mixture of phosphates, sulfates and potassium is being fueled by the popularity of growing plants indoors.
Once an industry focused on orchids, roses and tomatoes, hydroponics is now being propelled into mainstream business by marijuana.
"I used to be put off by seeing the work I did always show up in marijuana-focused stores," said General Hydroponics founder Lawrence Brooke, a scientist-turned-entrepreneur who has been developing fertilizers and water-pump systems since the 1970s.
But today, as business booms, he acknowledges the revolutionary influence of soil-free growing methods.
"People who grow medicinal cannabis know it's the most powerful tool," Brooke said. "Farmers ought to be paying attention."
He is among a cadre of business owners and gardeners who have brought Sonoma County to the forefront of a national surge in indoor farming.
More than two dozen local stores with names like Gonzo Grow in Santa Rosa, House of Hydro in Petaluma and Revolution Hydroponics in Sonoma have opened, many during the past five years.
"God knows, we've seen them pop up everywhere," said real estate agent Barry Palma, senior vice president at Cornish and Carey Commercial.
That boom is fueled by a steady hum of water pumps bringing nourishment to an unknown number of marijuana plants under an untold number of roofs.
"The vast majority (of hydroponic retailers) are doing business legally, but they're capitalizing on an illegal market," said Santa Rosa Police Sgt. Mike Tosti, who runs the department's narcotics unit.
Hydroponic gardening was developed as a way to get nutrients directly to plant roots.
The English philosopher and scientist Francis Bacon first published a study on such methods in the 17th century. A UC Berkeley scientist coined the term hydroponics in 1937.
The method avoids the soil that breaks down nutrients into elements plants can absorb. With hydroponic methods, the roots come in direct contact with nutrient solutions they can absorb.
Plants sit in pots of pebbles or shallow plastic bins. A constant stream of water delivers air and carefully crafted mixtures of elements plants need to thrive.
Plants are less hampered by pests. Water can be recycled.
"They just suck it up directly, optimizing the plant's diet, which optimizes growth," said Bob LaGasse, executive director of the Progressive Gardening Trade Association based in Manassas, Va.
He traces the beginning of the decade-long surge in alternative gardening techniques such as hydroponics to the Sept. 11, 2001, terrorist attacks, which drove many people to start growing their own food.
Organic and local food movements further bolstered the technique's popularity, as has high unemployment.
However, none of those factors has generated as much interest in growing plants indoors as marijuana.
"The activities of the medical marijuana industry have overshadowed the progressive gardening aspect," LaGasse said. "And a lot of single-purpose shops did open."
California led the way with the Compassionate Use Act of 1996, and 15 states have since passed medical-marijuana laws.
The recent referendum to legalize pot, Proposition 19, drove many entrepreneurs to open businesses ancillary to marijuana production, particularly after several polls showed significant percentages of California voters supported legalization, said David Solotky, General Hydroponics' chief financial officer.