Oaks are the Answer

The dwarf interior live oak (Quercus wislizenii var. frutescens) has a sturdy structure and thrives in rocky or poor soils common in the urban West. Photo: Sean Hogan

The Willamette Valley has a thriving export nursery industry. But most of that inventory is grown and bound for points east where cold winters and wet summers prevail. Plant those trees here in our mild winter, dry summer climate and the result is the drought-shocked urban canopy that can be seen around Portland and other western cities.

Other factors contributing to an ailing green infrastructure include the planting of canopy trees in greater numbers out of reach of irrigation, such as planting strips between sidewalk and street. Though our extensive “urban mulch” of pavement does help preserve ground moisture into the dry season, as historical sources of moisture—a hydroponic system of leaky clay sewer and water pipes—are replaced, questions follow like “why did most of the birch trees on my block just die?” And, whether due to a conservation ethos or ever-greater sticker shock at the water bill, many homeowners are cutting back on irriga...