Horse Rock Ridge ResearchNatural Area

Linda R. McMahan, Ph.D.

Retired, OSU Extension Service

Oregon State University

April 28, 2014

Perched on a mountain at 2700 feet in the western Cascade Mountains, the area, protected by the U.S. Bureau of Land Management since the 1980’s, provides a stunning contrast to the surrounding forests. My friend Tim and I revisited this outstanding natural place early in the year to view spring flora. Paintbrush, Castilleja hispida, partially

parasitic on surrounding vegetation.

The meadow persists as a mantle covering basalt lava flows 24 million years old! The shallow wet soils inhibit colonizing trees, but favor low-growing meadow plants.

Horse Rock Ridge is perhaps named for a basalt dike near the upper part of the reserve. From some views, it may resemble a horse or horses to some.

Upon entering the meadow after a short climb from the parking area, this was the first plant to catch our attention.

Fields of shooting star, Dodecatheonhendersonii, blanketed moist areas of the reserve.

Nearby, a less common early spring plant, Frittilaria lanceolata, was visible, protected under shrubs along the trail.

Poor soils foster delightful diminutive forms of usually larger plants. Pink-flowered and tiny rosy plectritis, Plectritis congesta, and blue-flowered, but also tiny blue-eyed Mary, Collinsia sp.

Other common wildflowers were small patches of bright yellow-flowered Lomatium utriculatumand drifts of Oregon fawn lily, Erythroniumoreganum.

Erigeron compositus

The striking cut-leaf daisy often appeared near the edges of basalt ledges.

“Weeping” basalt ledges provide habitat for water-loving plants.

Yellow monkeyflower, Mimulus guttatus, grows profusely in these areas.

Pretty meadow plants from the darker side. . .Top : Death camas, Zigadenus venenosus(now Toxicoscordionvenenosum), whose bulbs have been mistaken for the edible camas bulb. Bottom: Annual and parasitic naked broomrape, Orobanche uniflora, which surfaces to flower and producer seeds.

Forest edges hold other interests. Here a manzanita, Arctostaphyloscolumbiana, borders the forest with die-back in unfavorable years. Douglas fir, Pseudotsuga menziesii, produces cones, and a wild strawberry, probably Fragariavirginiana, flowers profusely.

The entire area offers outstanding views of the surrounding mountains. This photograph shows the view looking toward the central Cascade Mountains to the East. Horse ridge rock is in the foreground.

Although clear cuts for timber are common in the area, the meadow itself, nearly 83 acres, has been preserved and buffered with the help of local timber companies. Weyerhaeuser has granted an easement and surrounding old growth forest to help preserve a portion of this exceptional area.

On our way out of the reserve, we came across a rare sight in the forest. It was the first time I had seen the white-flowered form of this forest beauty, the fairy slipper orchid, Calypso bulbosa.

For more information . . .• http://www.portlandhikersfieldguide

.org/wiki/Horse_Rock_Ridge This website provides basic information and directions to the trailhead.

• http://www.npsoregon.org/kalmiopsis/kalmiopsis11/horserockridge.pdfAn article in Kalmiopsis magazine about this outstanding area. Includes a species list.

• http://www.fs.fed.us/pnw/pubs/gtr571.pdf Pictured at right, this publication by the Bureau of Land Management explains more about the area and provides a species list.

Thank you for watching!

• Copyright©, Linda R. McMahan, Oregon State University Extension Service

• This presentation can be used freely for educational purposes

• For other uses, please contact the author at viomusica@gmail.com

A native Saxifrage, perhaps Saxifragaoccidentalis.