The Portland Flower Show opened this week, providing winter-weary visitors with a glimpse of spring: acres of flowers, shrubs, grass, the sound of water running over rough stones, the smell of fresh earth.

To the visitors, it was heaven.

To the vendors, the show was a harbinger of big bucks to come.

Horticulture is now the fastest-growing segment of Maine agriculture, raking in $286 million last year, including retail and wholesale sales and services.

Income within the industry grew by an average of 32 percent per firm, according to Anne Gibbs, Maine’s state horticulturist.

Put that in perspective: Maine’s blueberries are a $44 million annual crop; potatoes are $100 million; and the entire Maine livestock industry is $262 million.

This explosive growth is no Maine fluke. Horticulture has become the largest agriculture sector in four other New England states: Connecticut, Massachusetts, New Hampshire and Rhode Island.

Eight years ago, Chris Paquette of Robin’s Nest Aquatics in Hollis sold $7,000 worth of water gardens. “This year, we’ll do at least a half-million dollars,” he said.

Chase Campbell of Gnome Landscapes and Design in Falmouth had 11 employees a decade ago. This summer, he will have 65.

“We’ve had an explosion,” said Jeff Marstaller of The Flower Center in Cumberland. His business has jumped from two small greenhouses to seven large ones in the last decade.

“I remember when a landscaped home was one that had a forsythia bush in the front yard,” reflected Marstaller. “People used to drive by to see it when it was in bloom.”

Not so today, said Marstaller.

American consumers spend two to three times more on outdoor plants and flowers than consumers in other developed nations – $203 a year per household, according to national statistics.

Marstaller’s exhibit “Vacationing where other people live” won the show’s kitchen-garden award and theme award. It featured driftwood from Sebomook Lake crafted into a covered porch enclosed by a twisted stick fence around a garden filled with green beans on poles, lettuce, cabbage, pumpkin and Swiss chard.

The exhibits throughout the acres of space at the Portland show ranged from formal, carefully manicured estate and zen gardens to Marstaller’s wild kitchen garden to a chicken coop, with live chickens and a crowing rooster, surrounded by a tropical garden.

“Our customers today are more sophisticated and educated,” said Marstaller. “They know what they want and they want something different.”

That observation was echoed by Shirley Brannigan of Allen, Sterling and Lothrop in Falmouth, the oldest seed house in Maine, established in 1911.

“Our clientele is expecting something new,” Brannigan said. “We have been growing specialized grass seed, unique outdoor shrubbery and plant materials.” Brannigan said her business has more than doubled in the last five years.

But Marstaller said the distinction of “two Maines” is clear when it comes to horticulture. “It’s huge in the south. No so much in the north,” he said.

And that’s not just a casual thought: State agricultural statistics back it up.

From 1974 to 1997, nursery and greenhouse businesses exploded, but at a far more dramatic rate in southern Maine. During that time, Cumberland County’s sales grew from $849,000 to $7.58 million, while Penobscot grew from $337,000 to $2.39 million. Aroostock County went from $177,000 to $1.5 million.

If you think that horticulture is far divorced from agriculture, listen to the story of Winterwood Farm in Lyman.

The St. Onge family has been farming in Lyman since 1686 and as part of diversification, a black walnut tree grove was established. “These trees need lots of compost,” said Allan Hayes of Winterwood. The search for just the right compost resulted in the creation of an agriculture-based business that is now making a larger profit than the farm itself.

Taking manure and bedding from 100 area farms and adding crushed shells of shrimp, crab and lobster from coastal processing plants, aging and screening the product, the farm has created a top-grade compost.

“Last year, four garden centers carried our bagged product,” said Hayes. This year, Winterwood Farm supplies 118 garden centers throughout New England and upstate New York.

“We are riding the wave of horticulture and the wave of organic,” said Hayes.

But success breeds success and many of the Portland Flower Show vendors said that competition is heavy. “Especially in hardscapes,” which is stone and concrete worke, said Campbell of Falmouth’s Gnome Landscapes. “Everyone does stonework now.”

The Internet and dozens of home gardening shows on cable television have also peaked consumers’ interest and created a more savvy customer.

“They’ve already checked it out and they know what they want,” said Campbell.

Matthew Chase owns Anchor Fence Co. in Kennebunk, which produces cedar fencing and furniture and has grown by 50 percent in the past year.

“I think that especially after 911, people became more interested in their homes. People were afraid to travel and interest rates were low,” he said. “They began putting their vacation into their yard.”