Sweet peas look innocent enough. Their petals perch like little butterflies on long, curly vines. And the delicate blossoms, in shades of pink, lavender, maroon, blue, and white, don’t seem very impressive on their own. But put a bunch of them together and watch out – if the ruffled bouquet doesn’t seduce your senses, the heady fragrance will.

Susan Keating of Surry knows all about the flower’s power. She has built a successful business, Sweet Pea Gardens, around the unassuming Lathyrus odoratus, a fragrant annual that captured her attention as a girl in New Brunswick.

Keating’s grandmother would hold high tea in the parlor of her home, and young Sue would listen to the ladies gushing about their gardens, especially their sweet peas.

“As a child, I didn’t run out and plant them, but it was a memory,” she said, sitting in her dining room, a framed copy of a Martha Stewart Living feature on Sweet Pea Gardens hanging on the wall behind her.

That memory stayed with her after her family moved to Massachusetts, and then later, as she worked in corporate marketing in Manhattan. But it wasn’t until her new husband, Pat Keating, was transferred to Maine that she was able to turn her attention to gardening.

In 1992, the couple moved to Lamoine, and Susan and Pat both worked at The Jackson Laboratory – she in marketing, he in construction management. They had a large plot of land, and Susan started a garden. Two years later, she started selling flowers and pickles at the Bar Harbor farmers market, and she loved the community atmosphere. Her friends from New York would come up to visit and tease her about her country lifestyle, but it didn’t bother Keating a bit.

“I just got hooked on it,” she said, smiling.

For several years, Keating worked as a marketer by day, gardener by night. It was going well, until she found out she was pregnant with her daughter, Maggie, who is now 61/2.

“When I had my baby I really had to make a decision,” Keating, 38, said. “It’s been the best decision I’ve ever made. Not that I didn’t like working at the Jackson Lab, but this is much more me. … It’s a hobby turned into a passion turned into a business.

The Keatings had moved to Surry, where they had enough land for gardens and a barn they could turn into a shop. In 1998, they hung a sign in front of their house, and it attracted the attention of several influential members of the gardening community, including Martha Stewart, who has featured Keating on her TV show and in her magazine. Belfast-based photographer and author Lynn Karlin included Keating in her book, “Gardens Maine Style.” Sweet Pea Gardens was featured on the cover of the February/March issue of Garden Design magazine, and Keating’s flowers will be the focus of an upcoming article in Country Living magazine.

“I think it’s the niche,” Keating said of the publicity. “There’s so many people who love sweet peas and so few people who specialize in them.”

Keating now grows more than 20 rows of the high-climbing, fragrant annual – between 25 and 35 cultivars a year – as well as the nonfragrant perennial variety, Lathyrus latifolius, which comes in shades of pink and white and grows up to 15 feet tall. In addition, she grows up to 40 different types of cut flowers, which she sells in cottage-style bouquets. But sweet peas are still her first love.

“Sweet peas in general are just a fabulous cut flower for the fragrance and the beauty,” Keating said. “You can keep on cutting and cutting and cutting.”

In fact, you should keep on cutting. She and her staff of six to eight seasonal employees cut the flowers every two days to encourage blossoming.

“On sweet peas, you never want to see pods,” Keating said.

If you’re a seed-saver, Keating said, you should be selective with sweet peas.

“If you’re going to save your seeds, let those pods get swollen and dry on the vine,” she said. “The problem with saving seeds is that if you let them go to seed, you’re not going to get any more flowers.”

And the flowers are the best part. Though they’re relatively small, they come in an almost endless range of colors and variations. There’s the true-blue “Azureus,” the red and white striped “America,” the creamy “Mrs. Collier,” and the big-blossoming favorite “Spencer Mix,” with a variety of blue, purple, white and pink blooms.

“I love them because they have the widest range of colors,” Keating said.

In addition, the Spencer Mix is reliable, it can be planted as soon as the ground is workable, and it has longer stems and larger flowers.

“People read all the articles and hear all about these antique or heirloom varieties and they tend to get all romantically swept into that,” Keating said. “One thing to remember is those antique varieties have small blooms. … But some people are just hooked on the heirlooms and they don’t care that they’re smaller.”

As a compromise, Keating usually urges gardeners to plant a combination of heirlooms and the Spencer Mix. She does admit that the antique varieties are a nod to the sweet pea’s rich history, which dates back to 1699, when a Sicilian monk named Francis Cupiani discovered a purple and maroon flower growing in his garden.

He liked it so much that he kept the seeds and gave them to a botanist friend. From there came “Painted Lady,” a pink and white flower that popped up in the early 1700s. Later, Henry Eckford, a Scottish breeder, introduced new colors and a bigger, bolder structure to the flower.

“He did more than anyone to popularize sweet peas,” Keating said.

The flowers that followed in the 1800s are what people commonly refer to as heirlooms, such as “America,” “Lady Grisel-Hamilton,” and “Mrs. Collier.” The turning point in sweet pea production came about 200 years ago, when the gardener for the Earl of Spencer discovered a large, frilly blossom that sprung up among his sweet pea plants. He saved the seeds and developed what is now known as the “Spencer” variety, which is a favorite of the cut-flower industry.

Keating’s current favorites are “April in Paris,” a white bloom with a maroon edge sold by Renee’s Seeds, and “Oban Bay,” a large, heavenly white with a light blue tinge.

“It’s very beautiful,” she said.

As she walks around her garden on a cool, early May day, only a few sweet peas have germinated along the tall trellises, but Keating knows it will be a good season. She has developed an almost foolproof formula for growing the flowers – and the results are the kind of thing elderly women still brag about over tea. Her grandmother would be proud.

“It’s a dream come true,” she said.

Sweet pea tips

Susan Keating offers the following tips for growing great sweet peas

. It’s best if you prepare your flower bed in the fall. Pick out a spot with full sun and fertile, well-drained soil. Raised beds work well. If you didn’t prepare the soil in the fall, either plant the sweet peas in pots or amend an old garden bed with compost and hope for the best. In general, sweet peas thrive under the same conditions as vegetables.

. Add a lot of organic matter. Manure works well, but Keating’s favorite is seafood compost.

. Keep the soil’s pH between 6.5 and 7.0

. Plant the seeds as soon as the soil can be worked – mid-April to mid-May. If you’re reading this now, you’ll want to get your seeds in the ground as soon as possible.

. Soak seeds overnight before planting. Some people recommend nicking the seeds with a sharp knife, but Keating has never done it and she’s had excellent results.

. Drain seeds and sprinkle liberally with inoculant, which helps them germinate faster and grow more vigorously.

. Plant seeds 1 inch deep and 1 inch apart.

. Sweet pea vines grow between 6 and 8 feet tall, so they will need a trellis system. If planting in rows in the garden, stake and reinforce with chicken wire. If planting in patio pots, use a wide pot that can accommodate an odalisque or a group of gray birch twigs (called “pea brush”) as support.

. When growing from seed, it will take between two and three weeks for the plants to germinate. Don’t worry if they seem to be taking a long time.

. When growing from seedlings, sprinkle a teaspoon of organic phosphorous (Keating recommends BioPhos) into the planting hole.

. If your space is limited, plant in patio pots filled with a mix of potting soil and seafood compost. Add a little time-release fertilizer to the soil (Keating recommends Osmacote).

. In June, feed seedlings twice with diluted fish emulsion. If your sweet peas are planted in fertile soil, you won’t need to feed them again. If the soil is poor, they will need regular feedings.

. Transplant seedlings by mid-May.

. If you plant by mid-May, plants should bloom from mid-July to September.