Juniper trees are a relatively uncommon tree in Washington State. Much of eastern Washington is too dry and/or too hot in the summer so that there are only a few isolated stands of Juniperus occidentalis (western) and even rarer Juniperus scopulorum (Rocky Mountain). The western junipers are limited to the Juniper Dunes Wilderness just north of the Snake River and a few isolated spots in the Snake River Canyon and Wallula Gap where the Columbia River cuts through the Horse Heaven Hills. The Rocky Mountain junipers are limited to small very isolated stands along the Columbia River from Chelan to Vantage.
Western Washington has Juniperus maritima (Adams, 2007). The south facing slopes in Anacortes' Washington Park is the largest stand I have observed.
Juniperus maritima in Washington Park
The south slope of the park has an alpine feel with open meadows of grass and moss between stands of trees and rocky outcrops. The junipers are the dominant tree over large areas with scattered stands of Douglas fir and madrone.
View to the west toward with the southern end of Lopez Island in the distance and the Straight of Juan de Fuca.
View to the southeast and of Mount Erie
Burrows Pass and Burrows Island
Lichen covered rock and junipers
Serpentinite of the Fidalgo Ophiolite
Anacortes is well within the rain shadow of the Olympic Mountains. The relatively low rain fall and south slope aspect of the location contributes to the presence of the junipers. The junipers are also present on south slopes in dry areas of the San Juan Islands and Gulf Islands.
The geology of Washington Park provides another advantage to the junipers. Serpentinite chemistry is a harsh plant environment due to the unusual ration of calcium and magnesium as well as a lack of phosphate bearing minerals. That chemistry limits other trees and allows the junipers a competitive advantage as the junipers have a higher tolerance to these harsh conditions.