As March marches toward April, an ancient urge makes itself felt, becoming more insistent as the days lengthen: the urge to dig in the ground, to plant, to inhale the fragrance of flowers, to savor a multitude of shapes and shades — blue, purple, red, pink, yellow, orange, green.

In Maine, the long dying of winter known as mud season can be a frustrating time for gardeners. Elsewhere there are reports of spring, but here there are piles of dirty snow, and the ground is cold.

But there is hope. The annual Bangor Garden Show is around the corner — March 31 through April 2 at the Bangor Auditorium and Civic Center — and nurseries in the state are busily preparing for the short, hectic growing season.

At Surry Gardens, outdoor plants are hidden under piles of straw, and bags of peat moss are stacked high. Inside the greenhouses, there is welcome escape from a gray, raw March day — humid, mild air, the smell of earth, an assault of color. Magenta bougainvillea drips from hanging baskets, thick, white butterfly orchids disclose pink “lips,” and tiny sprigs of green line countless plant flats.

Jim Dickinson, who founded Surry Gardens in 1977-78 when he was fresh out of the defunct Nasson College in southern Maine and didn’t know how he was going to earn a living, now has nine greenhouses, with plans for two more. His staff ranges from five in winter to 35 in summer, and he can’t begin to count how many truckloads of peat moss bags he uses. A tubing system delivers the right amount of water to each hanging basket, a computer keeps track of which varieties sell best, and a generator prevents power outages from being disasters.

The business has grown like — well, like a weed.

“People keep moving in, and it gets a little bigger and a little bigger,” Dickinson said.

He has customers from Deer Isle to Bangor. Gardeners from estates in the Camden-Rockport area come to buy plants. Landscaping work accounts for a major share of the bottom line. Mainers like to garden, it seems, and there’s always call for geraniums, pansies, begonias — or something more exotic.

A love for the offbeat in the botanical world is evident as Dickinson shows off double white marguerites with spidery edges and Himalayan blue poppies. A few years ago, garden centers were in a rut, he said, but now that distributors are more competitive, more varieties are available — there are 20 to 30 kinds of fuchsias alone. He pointed out a yellow trumpet-shaped clivia that was advertised at $400 apiece, he said, though he got his plant for considerably less. He plans to pollinate the flowers and wait for the seeds to ripen.

Propagating from cuttings and seeds starts in late fall and continues through the winter. Houseplants sell all winter, and gardening starts the end of April. “It takes all winter to get ready for spring,” Dickinson said. The busiest time, of course, is the end of April to October.

While Dickinson ponders how to satisfy his customers’ fantasies, Phil Stack, manager of the Roger Clapp Greenhouses at the University of Maine in Orono, has perhaps a harder task — satisfying the competing demands of professors for research space.

Both sustainable agriculture involving weed and pest management in potato fields and ornamental horticulture are represented with research projects at the greenhouses, which provide a controlled environment in the winter.

The research has increased dramatically, Stack said, as renovations started about eight years ago have made the greenhouses more usable. Electrical and plumbing systems have been brought up to date, and an effort is under way to upgrade the plant collection. Greenhouses 1 and 2 are being improved, with new benches, and reorganized. With a more efficient cooling system, they can be used for research in summer as well as winter.

The 1-acre site, in the middle of the Orono campus, includes a small building with offices and lab, six greenhouses with work area, and outdoor gardens. Stack refers to the complex as a “living laboratory.”

His wife, Lois, an associate professor of horticulture in the adjacent Deering Hall, plants the outdoor gardens and uses them as a teaching aid. One of the beds is used as an All-America Selections Trial Garden, one of several national sites — and the only one in Maine — for testing the performance of seedlings.

While managing the greenhouses and facilitating the research of UM faculty, Stack does his own research on pest management, trying to develop resistant plants and biological controls, so chemical agents will be less and less necessary.

“Land-grant schools all have greenhouse facilities — it’s an important part of their program,” Stack said. He sees the UM greenhouses as having three major functions: research, teaching, and public service. They are open to the public, and Stack gives tours to schoolchildren, usually from the end of March through May. He gets from 10 to 20 groups a year, and they make a day of it, also visiting the UM planetarium and dairy center.

Surry Gardens and the Roger Clapp Greenhouses are two of the 19 commercial nurseries and seven public gardens listed in a new brochure, “Maine’s Horticultural Highlights.” It was developed by Karen Mitchell and Steven Jones of Fieldstone Gardens in Vassalboro, Michael and Gail Zuck of Everlasting Farm in Bangor, and Gail and Rick Sawyer of Fernwood in Swanville.

Criteria for inclusion, Mitchell said, are at least five years of experience, preferably in Maine, displays for public viewing, some unusual plants, hardy plants, and a commitment to providing public education. The brochure, which is not comprehensive, will be updated. “We would love to have more (entries) from northern Maine,” Mitchell said.

She said the group was inspired by a brochure the Cooperative Extension in Vermont has produced for years. The Maine brochure is privately funded and will be distributed at tourist centers around the state. Anyone interested in obtaining one can send a self-addressed stamped envelope to: Maine’s Horticultural Highlights, 620-P Quaker Lane, Vassalboro 04989-9713.