"You definitely have to have the right mentality for [collecting cacti]. But just the fact that not everybody does it makes it fun," he says from his Houston home. Visitors step from his back door into his bright nursery, where he has hundreds of cacti and succulents in green pots. Most he has grown himself from seed, but some of the older and rarer varieties were field collected - that is, harvested from the wild. He and his wife, Lyn, spend every free moment tending the plants, which he estimates are worth about a half a million dollars. He isn't interested in field collection, though he admits he is not above buying field-collected plants. Instead, Mr. Thomas spends most of his time propagating the species he has.
"Used to be you could just go scrape them off the desert, just have at it. It's not like that anymore," he says.
Field collection is a tricky proposition. Instead of the lassos and horses used to rustle cattle in wild West days, today's cactus rustlers use shovels and pickup trucks.
Large barrel, prickly pear, and saguaro cacti are the most sought-after varieties for desert landscaping, called xeriscaping, which has taken off in cities such as Phoenix, Tucson, and Las Vegas.
Because of Arizona's strict laws regarding cactus harvesting, landscaping suppliers - who find it easier and faster to dig up full-grown plants in the wild than propagate them in nurseries - turn to unregulated Texas.
Between 1998 and 2001, for instance, nearly 100,000 succulents worth an estimated $3 million were shipped to Arizona from Texas.
Then there are those who pluck a cactus from a state or national park and don't realize that it's against the law, says Danny Contreras, a park ranger at the Franklin Mountains State Park near El Paso. While he has caught people driving off with truckloads of barrel cacti, yucca plants, and ocotillo trees, a more common occurrence is a solitary person digging up a single cactus for medicinal purposes or to plant in their garden.