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Lake Wilderness Arboretum

Maple Valley, WA · 42 acres Arboretum

History & Context

Lake Wilderness Arboretum began without land, money, or institutional backing. In 1965, George Tersiisky, a Bulgarian immigrant, and a small group of supporters including Kent Mayor Isabel Hogan organized the South King County Arboretum Foundation as a 501(c)(3) nonprofit. Their goal was to establish an arboretum in south King County.

The land they eventually secured had its own history. In the 1890s, one of King County's largest logging mills operated at Lake Wilderness. In 1926, the Gaffney brothers began developing a resort on the lakeshore that grew into a complex of about sixty rental cabins with a golf course, bowling alley, dance hall, and restaurant. The Lake Wilderness Lodge was built in the early 1950s, with a 2,400-foot airstrip added to accommodate air taxis. By the 1960s the resort had declined and King County purchased the property in 1964.

In October 1967, King County approved the concept of an arboretum on over 40 acres of the former Gaffney property, centered on the old airstrip area adjacent to the Lake Wilderness Lodge. Final approval came in 1969. An architect's overall design was completed in 1970, and volunteers began implementing it in sections. The resort's old corral became a nursery for propagating trees and shrubs. The first plant sale, held in 1971 on the boardwalk at the Golden Steer Restaurant in Kent, established an annual tradition that remains a major funding source.

In 2003, the land transferred from King County Parks to the newly incorporated City of Maple Valley, and the name changed from South King County Arboretum to Lake Wilderness Arboretum. The Foundation name followed in 2007. The Tribal Life Trail, an ethnobotanical garden focusing on plants used by native peoples of the Puget Sound area, opened in 2010 and has been maintained by WSU Extension Master Gardeners since 2008.

Today the arboretum covers 42 acres: five acres of developed gardens and 30 acres of forest trails. It operates through a Joint Use Agreement between the Lake Wilderness Arboretum Foundation and the City of Maple Valley.

Garden Sections

Smith-Mossman Western Azalea Garden

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Western azalea collection.

Est. "

Rock Garden

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Alpine and rock garden plantings.

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Woodland Garden

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Shade-tolerant plantings under canopy.

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Legacy Garden

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Mixed specimen plantings.

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Perennial Garden

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Herbaceous perennial displays.

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Tribal Life Trail

Maintained by WSU Extension Master Gardeners (King County)

Ethnobotanical demonstration garden focusing on plants used by native peoples of the Puget Sound area. Trail-style layout highlighting food, medicine, utility, clothing, and ceremonial uses of five...

Est. 2010 (clearing and initial plantings began 2005)

Children's Discovery Forest

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Natural play and discovery area for children.

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Forest Reserve

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30-acre second-growth forest with trail network. Not wheelchair accessible.

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Visit Log (2 visits)

April 20, 2026

GDD₃₂: 1531.6 Station: issaquah Warm and dry. High 71°F, low 54°F. No precipitation. Light winds.

First visit to Lake Wilderness Arboretum. Arrived late afternoon and spent a fair amount of time walking the grounds. The arboretum sits on the site of the former Gaffney Resort, and at 42 acres it has a mix of developed gardens and forest trails that gives it a different character from the urban gardens I usually visit.

The Tribal Life Trail was a highlight. It's an ethnobotanical garden maintained by WSU Extension Master Gardeners that focuses on plants used by native peoples of the Puget Sound area, organized by use: food, medicine, utility, clothing, and ceremonial. The interpretive signage covering Western Red Cedar, Douglas Fir, Salal, Vine Maple, and Western Sword Fern was well done.

The Metasequoia glyptostroboides 'Ogon' was leafing out with striking golden-yellow foliage. There's a nice mature Acer griseum that was still at bud swell while most other maples were in full leaf, which is typical for paperbark maple. Plenty of rhododendrons in bloom, several magnolia species flowering, and the woodland garden had Anemone nemorosa 'Vestal' in peak bloom. The collection is diverse for a volunteer-run arboretum, with some genuinely uncommon specimens like Rhododendron pseudochrysanthemum and Cedrus brevifolia 'Kenwith'.

Notable Findings

  • Tribal Life Trail ethnobotanical garden is well-conceived and well-maintained; good example of ethnobotanical interpretation
  • Metasequoia glyptostroboides 'Ogon' golden foliage emergence is a phenological marker worth tracking
  • Acer griseum late dormancy break confirmed (bud swell at 1531 GDD₃₂ while other maples in full leaf)
  • Good diversity of magnolia species and cultivars: M. macrophylla, M. stellata 'Royal Star', M. liliiflora 'Nigra', M. 'Elizabeth'
  • Rhododendron pseudochrysanthemum (Taiwan endemic) in full bloom
Return notes (5)
  • Return in June for peony bloom and hydrangea development
  • Explore Forest Reserve trails more thoroughly
  • Document western azalea bloom timing in Smith-Mossman Garden
  • Check Acer griseum bark condition and full leaf development
  • Photograph Tribal Life Trail interpretive signage for reference

May 15, 2026

GDD₃₂: 2162.2 Station: issaquah Cool and wet. High 51°F, low 46°F. 0.56 in precipitation.

Brief return visit on a cool, rainy morning. Mostly a drive-by with a quick walk. Noted Cotoneaster dammeri in full bloom along pathways and Euonymus alatus 'Compactus' with flower buds developing. Not a thorough walk-through; weather kept this visit short.

Return notes (3)
  • Return in summer for a proper second visit
  • Check Acer griseum full leaf and bark detail
  • Look for summer-blooming perennials in the Perennial Garden