Once a year, you can explore rare ecosystem of Thurston County's Glacial Heritage Preserve on Prairie Appreciation Day.

Location: Mima Mounds and Glacial Heritage preserves, Littlerock, Thurston County

Length: Five miles of trails at Mima Mounds (including a half-mile paved loop); seven miles at Glacial Heritage.

Level of difficulty: Level to gentle grade.

Setting: The 637-acre Mima Mounds Natural Area Preserve, famous for its mysterious mounds, also features a rare prairie habitat. When the white settlers arrived in South Puget Sound, along with dense forests they also encountered open rolling prairies. Native Americans managed these grasslands for thousands of years with periodic burns to encourage the growth of plants used for food and to provide habitat for deer and elk. This careful management of the prairies developed a unique ecosystem with several species and plant communities that exist nowhere else. This prairie landscape once extended from just south of Tacoma to the Chehalis River drainage, but now it makes up only about 3 percent of the land in South Puget Sound.

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Highlights: Wildflowers and butterflies make May and early June prime times to visit the prairies. The nearby 1,300-acre Glacial Heritage Preserve hosts the annual Prairie Appreciation Day from 10 a.m. to 3 p.m. this Saturday. (An excellent example of the Puget Prairie ecosystem, the Glacial Heritage Preserve is accessible to the public only for this annual celebration.)

Bring the family for lots of activities. Go on a wildflower walk, hear how Native Americans harvested prairie plants, and get up close and personal with small prairie creatures. Learn how the prairies are being restored and managed, or attend a talk to hear theories about what caused the mysterious mounds on this area’s prairie landscapes. Wander out among the flowers by yourself, and then hop a hayride back to the parking lot. Explore a five-mile, self-guided interpretive trail, or kids can check out fun, informative activity stations along the shorter two-mile trail.

Facilities: Vault toilet at Mima Mounds Preserve.

Restrictions: No pets, horses, bikes or plant collecting. Please keep on trails. During hot weather, bring water, sunscreen and a hat.

Directions: From Interstate 5 about 10 miles south of Olympia, take Exit 95. Go west on Maytown Road Southwest 3.8 miles through Littlerock to the “T” intersection. To reach the Glacial Heritage Preserve, turn left on Mima Road, go 2.7 miles, and turn left onto an unmarked gravel road. Drive to the end of the road and park near the gate. To reach the Mima Mounds Natural Area Preserve, turn right at the “T” intersection on Waddell Creek Road Southwest, go .8 miles north, and turn left.

For more information: 360-357-6280 (Nature Conservancy). Websites: www.southsoundprairies.org, www.prairieappreciationday.org or www.nature.org. The Nature Conservancy and Friends of Puget Prairies have volunteer opportunities at Glacial Heritage Preserve that let you access the area year-round.

Renton-based freelancer Cathy McDonald, a geologist by training, has written about science and nature travel for 20 years. She’s currently a travel guidebook editor at Rick Steves’ Europe Through the Back Door. Contact her: nwwriter@hotmail.com