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May 19, 2007 California's "Sierra iris" (Iris hartwegii) occurs at intermediate elevations all along the western Sierra Nevada mountains. It lives in the thick bed of pine cones and fallen needles on the floor of yellow pine forests and nearby favorable environments. You'll usually find Sierra iris growing as individuals or clumps of single plants. Each year, only a few of the iris bloom in little patches of sunlight. But under certain conditions, a much more dense and colorful flowering takes place. Forest and woodland-dwelling Pacific Coast native iris like I. hartwegii respond quickly to increased sunlight. A higher percentage of the individual plants flower and set seed. Forest fires, clearcuts or roadways open up the canopy and for several years allow in more direct sunlight. With more seed and continued sunlight, iris plants flower in abundance, until the woodlands regrow and a new canopy once again captures most of the direct light before it can reach the forest floor.
During the last decade, many sections of California's Sierra Nevada yellow pine forest were selectively "thinned" as part of lumber industry and U. S. Forest Service - Department of Agriculture management programs. Remaining trees are more widely spaced. In some areas, virtual carpets of yellow Sierra iris blanket these new artificial meadows.
The photos below were taken along state highway 20 in Nevada County in mid May. Sierra iris were abundant all along the road to the Rock Creek nature trail, some 6-7 miles above Nevada City, at about 4,000 feet elevation. Remnant stumps show the forest was recently much more dense. Click any of the photos to see a larger version in a new window.
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