Pirates of the trees.

New York's tree thieves will be in for a rude awakening if they hijack a "free" Christmas tree from alongside the Long Island Expressway this winter. Instead of the gentle scent of pine, they'll be taking home a stench worse than a dead skunk in the middle of the road.

Environmental specialists at the state's Department of Transportation (DOT) are tired of their trees disappearing - particularly during November and December - so they're counterattacking. Armed with a vile recipe created at Cornell University's plantations division in Ithaca, New York, state landscapers slather roadside trees with a harmless but hideous coating aptly named the "Ugly Mix" (containing, among other things, hydrated lime and food coloring). Says Gary Gentile, senior New York DOT landscape architect, "When they've been coated with Ugly Mix, the trees look like a three-year-old kid sprayed the hell out of them with something putrid. Think vomit."

As visually displeasing as this theft-prevention may be, it's less stomach-churning than the DOT's second, albeit invisible step. Using sprays favored by hunters seeking to disguise human scent, land-scapers douse targeted trees with an odor that's unnoticeable in the cold, yet unbearable when it starts to heat up, say, in your living room.

"It's more odoriferous than cat urine," remarks Gentile. "And the warmer it gets, the worse it smells."

Tree theft is a problem that is by no means limited to Long Island - or the United States. In New Zealand, for example, native palms are regularly stolen and then sold on an extensive black market, forcing anxious arborists to insert computer chips under their trees' bark for identification. In South Africa, laws have recently been passed requiring microchipping of certain rare, native cycads and palms.

Back in the U.S., however, the problem is getting serious. "We'll plant a tree before lunch, and after lunch it's gone," complains David Wohlbach DOT environmental specialist in Poughkeepsie, New York.

Tree thieves, it seems, are not easily dissuaded. "We don't like having to spray trees with nasty smells or Ugly Mix," admits Wohlbach. "But people on Long Island have no problem stopping their cars and popping out a tree from the side of the road. Even when the trees are wired down with chains or stakes, some people will just, cut the top eight feet off of a 30-foot tree."

The future of public tree planting, concludes Wohlbach, depends on adaptation to adversity. "Landscapers," he predicts, "are going to have to start buying plants with really long thorns." CONTACT: New York Department of Transportation, Building 5, State Office Building Campus, Albany, NY 12232/[phone].