For 50 years, "seeing the color" has been a personal mission for Ray and Donna Solt of Albertville, Minn., who last week marveled at autumn's reds, oranges and yellows from the banks of the St. Croix River.

"You've got to take care of the beauty out here," Ray said, meaning he sees it as a human duty to appreciate the color palette of leaves as one fabled Minnesota season fades into another.

In coming weeks, trees and shrubs along Washington County's river valley will explode into their peak fall color. Nature's painting will attract thousands of people who bring their cameras and canoes to witness the splendor.

A few miles north of Marine on St. Croix's downtown village, at Crabtree's Garden Gate, business jumps 30 percent when color-watchers come cruising up Hwy. 95, said owner Jan Lynn. They don't always know the area — but they know what they want to see.

"It makes this time of year prosperous for me," said Lynn, who sells everything from bird seed to gourmet coffee to outdoor garden art. "We get so many people up this way who think we're the North Shore."

The best colors along the St. Croix River come from a handful of primary species, said Anton Benson, a regional resource specialist for the Minnesota Department of Natural Resources (DNR).

Sugar maples and pin oaks will produce vibrant oranges and reds. Green ash, hackberry and aspen bring yellows and golds. Brilliant reds can be found in sumac, a shrub, and Virginia creeper, a vine.

At William O'Brien State Park, camping is popular during the peak color season. Last weekend, 648 people came to the park for various activities on Saturday and 500 on Sunday, said manager Wayne Boerner.

"Colors do bring people out to our state parks," he said. "The progression coming down [the river], it's a beautiful time of year."

Many people, Boerner said, come to state parks for photographs, including large groups seeking to have their portraits taken against the amid the colorful array. Other people, drawn by the appeal of paddling through a canyon of color, come by canoe and kayak to William O'Brien.

In Stillwater, recently chosen by Travel and Leisure magazine as the nation's third-best city for fall foliage viewing, scenic color attracts crowds. The May-to-October peak tourist season accelerates noticeably when the colors come out, drawing as many as 40,000 more people to the city, said Barb Trueman of the Stillwater Convention and Visitors Bureau.

Patricia Arndt, a DNR spokeswoman, said colors generally peak from late September to mid-October. Heavy rain last spring will help make colors more vivid than usual this fall, she said, as will an onset of cooler nights.

"We encourage people to get out," she said. "The change is what we embrace in Minnesota. Just think of the variety we have here. It's crazy."

Kevin Giles • 651-925-5037