Madrones: Our Evergreen, Ever-red Trees

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Growing throughout the coastal mountains and inland valleys of western Oregon are stands of broad, heavy-limbed trees with peeling red bark and glossy ovate leaves. They are prominent and exotic-looking; they are often found interspersed with Douglas fir and western hemlock and tanoak in low-lying woodlands. They are evergreen in the sense that they do not defoliate in the fall, but instead shed their old leaves every July, after the new ones have fully grown in. Some of these strange red trees cling to cliff-sides and grow scraggly and shrub-like; others aestivate in sun-draped foothills and valleys and reach heights of a hundred feet or more.

The Pacific madrone (Arbutus menziesii), along with the shrubbier chinquapin tree and a couple of oaks, are the only broad-leafed evergreen trees native to Oregon. Their dark green, varnished leaves are sclerophyllous, meaning that they are adapted for water-retention: leathery, thick, impermeable, perfect for prolonged exposure to the sun. Pacific madrone is found from southwestern British Columbia all the way down to the coastal and western slopes of the Sierra Nevada, but no further south than Mount Palomar in San Diego County. It occurs most often at elevations below 3,000 feet, in sparse woodlands with rocky soils and plenty of light.

The sloughed-off skin of the madrone is perhaps its most striking feature. Termed “self-exfoliating” in the botanist’s argot, the tree aggressively sheds its papery bark year-round, exposing a smooth green trunk underneath that eventually turns brown, then orange, then a deep, burnished crimson. The exfoliation is thought to rid the tree of lichens and parasites, the latter of which there are several: bark-boring insects, pathogenic bacteria, pathogenic fungi that cause Arbutus canker, or heart rot, or butt rot; and much else. Like its relatives kinnikinnick and hairy manzanita, madrones in Washington put out small, bell-shaped flowers in late spring that ripen into clusters of reddish berries in the fall, and these fruits persist into the winter. Birds such as the Band-tailed Pigeon, Dark-eyed Junco, and Varied Thrush gorge on madrone berries when food is scarce. There is always something coming off the madrone tree, no matter the season—bark, leaves, flowers, and fruit. The madrone is perpetually shedding its accoutrements, yet it is ever green, and ever red.

Pacific madrones are slowly declining in their northern range, and many suspect that it is the suppression of fire that is to blame. Madrones are not fire-resistant trees—their flimsy bark does little to thwart flame—but rather they are fire-dependent: they rely on burns to clear away competition in the understory. Madrones seem to do best when growing in areas swept periodically by wildfire, especially those intense enough to kill more fire-resistant firs and pines. The upper portion of the madrone dies and burns in a blaze, but deep in the heartwood is a regenerative structure called the burl, which usually survives belowground. The wildfire consumes all that it can in the forest and eventually dies out. From the nutrient-packed burl sprout dozens of shoots, eager to outpace the others and tower over the fire-ravaged landscape.