Hagg Lake was created in 1972 when the Bureau of Reclamation dammed Scoggins Creek, a tributary of the Tualatin River. It sits at about 400 feet elevation at the foot of the Coast Range in southwestern Washington County, Oregon: 35 miles west of Portland. It is an area of mixed stands of Oregon White Oak, Big Leaf Maple, and various species of fir, depending on the elevation. Understory shrubs consist of snowberry, Indian plum, serviceberry, Salal and copious amounts of poison oak.
Iris tenax is found in the margins of the oak woods, in areas that have been cleared either through logging or road building activities. The most visible and accessible are the bountiful clumps on the roadside margins. Scoggins Creek is the type locality for butter yellow form Iris tenax f. gormannii.
All the Iris tenax I have seen along the Patton Valley and Lee Roads on the south side of Hagg Lake are typical lavender with dark violet veining and a yellow eye on the falls. I have seen no iris with yellow tones in this area.
On the roads that are at elevations higher than the lake, to the southwest and west, the colors of Iris tenax start to change. Yellow overtones begin to show up, creating "muddied" lavender flowers with a dark gold eye, and violet veining. The reverse also occurs with the lavender over yellow, which creates a very pretty, almost copper tone. There is an infinite amount of variation in shading - more yellow, or more lavender - in the clumps in any given area.
At the west end of the lake, the roads follow little creeks up into the Coast Range. Up Scoggins Creek and Tanner Creek roads, the predominant color is yellow, with some white, but almost no lavender. The yellow is a pale butter yellow with darker yellow veining and a dark gold eye on the falls. The white is a pure white, with very little veining and a gold eye on the falls.
A clear-cut area off Scoggins Creek Road has the best display of diversity I have seen in the area: bright lavender, butter yellow and every color in between except white. Up Tanner Creek Road, there were large patches of white, and pink blends (almost orange pinks) along with the yellows.