Howard County narcotics officers have made two big marijuana busts in the last month, one that took months to crack and one that was literally stumbled onto.

The latter, larger sting happened in mid-July, after hikers, trekking through a wooded area near the Rocky Gorge reservoir in Laurel, came across a crop of 207 marijuana plants.

Narcotics officers watched the field until, they said, Curtis Lee Dorsey, 27, showed up to tend it the next day. They caught him after a short chase on foot.

The "rather substantial grow," as vice and narcotics supervisor Lt. Tim Branning put it, was worth about $200,000. It lay in a 30-by-30-foot plot less than a quarter-mile back from Stansfield Road, in the Washington Suburban Sanitary Commission's Patuxent restricted watershed area, and far from any trail or natural opening.

Officials said the area--amid a thicket of pine and hardwood and dense overgrowth--was cleared of trees so light could come in, ringed by an unsophisticated mesh fence and protected from animals by a barrier of chemicals poured on the ground around the perimeter. Some of the plants were young and some were mature, indicating the crop had been there a while.

Larry Iager, captain for watershed protection in that area, said the WSSC has had similar incidents before in the 6,000-acre watershed area. "When you have something so large, on-foot observation of it is impossible," he said.

Branning, of the narcotics squad, said the bust was atypical anyway. Usually pot busts happen indoors--in crawl spaces, basements, garages--not in an outdoor garden so huge and established. Still, police had no knowledge of Dorsey, and were it not for the hikers, he might not have been discovered for a while. "I'm sure he was pretty confident that nobody would come across it," Branning said. " . . . We know that there's a lot of people out there we just haven't caught up with."

Police said they also found a quarter-pound of processed marijuana and growing lights in Dorsey's home, in the 8800 block of Bluebird Trace. He was charged with manufacturing a controlled dangerous substance, possession with intent to distribute and possession of drugs and paraphernalia. If convicted on all charges, Dorsey could be sentenced to 20 years in prison and fined $20,000, police said. He was released on $75,000 bond.

Police also arrested Philip Damon Knight, 26, of Rockville, who showed up with 245 Ecstasy pills, worth about $2,000, at Dorsey's house while it was under surveillance.

Last week, Howard County police arrested five teenagers in a drug bust at a Long Reach home. The police had been investigating for several months, based on citizens' tips, before they had probable cause for a search warrant. Such an investigation usually includes surveillance and undercover purchases.

When they raided the home, in the 8900 block of Footed Ridge in Columbia, police found almost 4.5 pounds of packaged marijuana, $3,000 in cash and two handguns. They arrested Devon Taron Conwell, 17, and charged him as an adult with possession with the intent to distribute marijuana, possession of marijuana and possession of drug-related paraphernalia.

Police also arrested a 15-year-old who drove up to the house with 15 small bags of marijuana and 12 rocks of crack cocaine, and three other teenagers--Terrance Crosby, 18; Thomas Lamont Moon, 19; and a 17-year-old, all of Columbia--who arrived with a half-pound of pot.

All the teenagers were charged with possession with the intent to distribute and possession. The 15-year-old was also charged with motor vehicle violations; he and the 17-year-old were charged as minors.

Conwell lives in the house with his parents, who were not home at the time of the raid. "Based on what we know right now," Branning said, the parents probably would not face any charges, though he said he anticipates additional arrests.

"We think we put a pretty good dent in the goings-on in Long Reach," Branning said. Staff writer Raja Mishra contributed to this report.