Driving along the tree-lined neighborhood in Portland, Oregon, in search of Sean Hogan and Parker Sanderson's house, it is difficult to determine where their garden ends and another begins. You gradually realize that there has been an expansion into a neighbor's backyard, over to another's front yard, a leap across the street to another, and so forth. Sean and Parker practice the art of neighborhood street-gardening - spilling your garden up and down the street onto your neighbors' property (with approval from the neighbors, of course). I once asked Sean what his favorite plant was and he responded without a moment's hesitation, but with a sly grin: "The plant that is in front of me at the moment." That is probably a rehearsed answer from a confirmed "plant geek," an endearing term bestowed on Sean and Parker by their friends and by professionals in the nursery industry. Sean and Parker are into "extreme plants" (the odd, the unusual plant) and "zonal denial" (stretching limits by testing a plant's adaptability to horticultural hardiness zones outside its range), a term they coined. A native of Portland, Oregon, Sean studied biology in college in California. From 1988 till 1995, he worked as a horticulturist at the University of California (Berkeley) Botanical Garden where he managed the New World, Australia/New Zealand, Africa, and California cultivar plant collections.

Parker is a native of Wales and spent time in Hawaii. He has a botany degree from the University of California at Davis and worked for the Davis campus arboretum for seven years. Sean spent time as director of collections of Portland's Hoyt Arboretum, renowned for the extensive conifer collection, and he and Parkerwere co-curators and planting designers of the Classical Chinese Garden, a garden of tranquillity and beauty walled away from Portland's busy streets. Both of them volunteer with numerous plant and horticultural organizations, write about plants, lecture, and travel to see plants in gardens and arboreta and in the field, both domestically and abroad. They have a commingling expertise in plants: for example, Parker is an authority on the Brodiaea alliance of Allium-like bulbous plants and Sean on Lewisia, native plants of western North America. The Lewisia interest extended to assisting in completion of LeRoy Davidson's book, Lewisias, and in sorting out taxonomic problems and the range of L. cantelovii, including the recognition of three botanical varieties (Davidson 2000). Sean and Parker founded Cistus Design in Portland in 1995, specializing in the design and creation of private and public gardens.

The business was expanded to include a nursery, now carrying about twelve thousand selections of plants and specializing in hardy tropical plants, broadleaf evergreens, Mediterranean, and Southern Hemisphere plants. Their tastes in plants are catholic. Sean and Parker's great skill is in facilitating the introduction of "new" plants - not necessarily plants that they have collected themselves, but the found, neglected, overlooked, and unpromoted plants. Sean says: There is such a candy store of plants available now and so many that are "new" that the market demand for plants is growing. Folks are not interested just solely in a few bold, or even native plants, for the garden. They want everything. There is a horticultural agenda afoot! Sean continues, tongue in cheek, "Parker and I tend to promote plants that are appropriate to our climate and any plants that we can force the climate to accommodate!" Helen Dillon (Dublin, Ireland), gardener, lecturer, and writer, has frequently visited the United States, including Portland. She says of Sean and Parker: One of the most extraordinary plant experiences of my life was a visit to Sean and Parker's plant collection when it was all housed, hig.