No trail marked our route; we parked on a friend's private property and walked for a spell up an old fire road, then plunged into the underbrush. Directions? We headed due southwest and uphill.

Veilleux waxed rhapsodic about the bay trees all around us: the manifold shapes of trunk, the lush color of the leaves when they catch the sun, and above all the scent, that wonderful smell. "I think Umbellularia californica is the most versatile and under-used California native plant in the landscaping trade," he said.

"Not in my yard," I replied. The mature bay reaches heights of 120 feet, and as wide. He allowed that regular pruning for size might be necessary. Mixed among the bays all around us, oaks and madrones whispered in the wind as if in awe of the bay's position as climax forest community, the ultimate dispatcher of other trees in the ecosystem.

I often see my own name written in native plants, but rarely so explicitly. Coffee fern (Pellaea andromedifolia) grows triangular fronds of delicate oval segments in a warm shade of green brushed with purple; we found them emerging from a vertical crevice in sheered-away rock like a spray of crystallized water. This plant also enjoys one of the most lovely and appropriate botanical names: the genus is Greek for "dusky," from the bluish-grey hue of the fronds, while the species name honors Andromeda, mythical beauty and princess of Ethiopia, the royal daughter chained to a cliff in sacrifice to a sea monster to appease angry gods. This long-creeping rhizome can act out a better Fay Wray than you'll find in the cinema, and can be used to great effect in the garden, e.g. between stones in a north-facing wall.

Suddenly, a thicket of poison oak blocked our way. At this time of year, the branches are bare of leaves, but Toxicodendron diversilobia still packs a wallop in its wood. This particular patch grew clear across the mountain face we were crossing, with no way around it.

"We just need to reach that ridge," said Veilleux. "It's not very far." Dubious at best, I thought. But he rolled down his sleeves, put on his gloves, and forged ahead.

I circled back downhill to look for a better approach, but there was none. No way to the top but through the toxic tangle. I did find a spot where the thicket looked thinner, but could see that the passage would still be severe.

I like to explore off-trail and to plumb the unknown; I do not like to become an itching ball of fire. Somewhere on the slope above me, I heard Veilleux thrashing through the poisonous branches and shouting "Almost there! Almost there!" Unable to throw my dermatology so casually to the wolves without good metaphoric support, I reminded myself that true character is built through adversity, true vision afforded only those who dare to transcend. And so I tucked my notebook and pen into my pack, pulled on my gloves, and looked for a very long minute -- then leaped.

I parted the thicket of menacing reddish-brown branches with a grimace and pushed through them for a minute or two, reaching the other side feeling fine despite what I considered my inadequate armor. Reunited, we made for the top of the ridge, where the tall trees gave way to a 10-foot micro-forest of coyote brush holding the perimeter of a mesa (recently cleared by bulldozers) with a commanding view of the East Bay hills sprawled between us and Mount Diablo like an odalisque.

We found what looked like an old Indian grinding stone beneath a gnarled, hoary oak on one side of the clearing, and stopped there for lunch. Absolute silence surrounded us, but for the cry of a hawk -- and looking out over so much natural Earth, I felt the shiver of my comparative youth beside these trees of centuries old, this landscape whose lifespan will be measured in millennia. Taking the view from among old oaks is good that way; it helps me change my units of thinking about time.

And yet mankind too has shaped this place: from the Indians renewing tired grasslands and oak woodlands by burning them to ranchers clearing woodland and brush for cattle; from developers chopping up parcels for a growing population to public utilities like EBMUD which owns and manages much of the Upper San Leandro watershed (in which we sat). Costs are high, both financial and spiritual, and the counties of Alameda and neighboring Contra Costa should be commended for the importance they have placed on the preservation of open space in this area.

Finally we descended the other side of the mountain toward the crease at Redwood Rd., our destination. At some point we must have crossed the Chabot-to-Garin regional trail, which runs north and south along that ridge, but we never noticed it, nor met another soul. Instead we drank in the shapes and colors of the woods: giant bouqets of aromatic bay, sculpted cappuccino trunks of madrone, and the myriad contortions of coast live oak. Several specimens of coffeeberry (Rhamnus californica), that hardy evergreen shrub, gave me a wink from the edges of the chaparral. Various clearings showed signs of passing deer or cattle, and the stamp of the hand of man: we encountered a young bay pruned into an 8-foot Christmas tree, and another topiaried into a 15-foot mushroom. Swooping down a final series of lightly wooded slopes, we reached the road and my car parked in the Chabot staging area near a tree farm doing a brisk business in yultide conifers.

Who can say where nature ends and civilization begins? We might as easily seek the source of the longest river and the voice of the hidden waterfall. Deep connections are found at these intersections, where urban gives on to wild with all the subtle gradient of the old year passing into the new. Safeguard these connections wherever you can find them -- we protect our roots even as we reach for the sunlight, our future.

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Geoffrey Coffey wrote this article from a bath of calamine lotion. He is the founder of the Madrono landscape design studio, a principal of Bay Natives nursery, and a freelance writer for the San Francisco Chronicle.

The Bonny Doon Ecological Preserve is the largest and most accessible of these unique habitats, with 550 acres and a network of trails open to the public during daylight hours. Walking these paths of heavy sand, one expects to hear the roar of the surf around every corner -- yet the ear meets nothing but the sound of a mountain breeze whispering through the surrounding woods.

Here we find a dominant population of the rare and endangered Bonny Doon manzanita (Arctostaphylos silvicola), an upright shrub from 5-15 feet tall with gorgeous silver foliage and a gnarled trunk of deep red vein-like branches. Sunlight shining at an angle through the leaves can cause this foliage to glow as if from within, rendering the landscape otherworldly and magical.

Bonny Doon contains several other endangered species that grow here and only here. The annual Ben Lomond spineflower (Chorizanthe pungens var. hartwegiana), for example, covers wide swaths of the sand with a bright pink bloom every spring, its small white flowers surrounded by spiny pink bracts that give this plant both its common name and its underlying color. Another rare spring bloomer is the Santa Cruz wallflower (Erysimum teretifolium), a biennial that grows a silvery basal rosette of needle-like leaves its first year, blooms a brilliant yellow in its second spring, then dries up and dies, leaving behind only a seed bank as the foundation for next year's growth.

Silvery color characterizes the leaves of many other members of the Bonny Doon flora, an adaptation that reflects sunlight and thus helps these plants conserve precious water in such dry and unforgiving conditions. Take the Ben Lomond wild buckwheat (Eriogonum nudum var. decurrens), another rare and endangered species, with delicate white hairs on its spoon-shaped leaves and a summer bloom of tiny white flowers held in dense heads like cotton balls. Wild buckwheats draw many native bees and other beneficial insects to feed on their flowers, which in turn attract a host of native birds to feed on the bugs; home gardeners seeking to attract wildlife, take note. While the Ben Lomond buckwheat is protected and not cultivated for the trade, Eriogonum is the largest dicot genus in California with approximately 250 species, many of which are available to home gardeners and are analogous wildlife magnets. Here in the Bay Area, ask your nurseryman for E. latifolium, our most common local variety, or E. 'grande rubescens,' a beautiful red-blooming selection from San Miguel Island.

Scattered widely throughout Bonny Doon's sandy open areas, the silver lupine (Lupinus albifrons var. albifrons) and the silvery-white fragrant everlasting (Gnaphalium canescens ssp. beneolens) yield further evidence of the prevailing color scheme. This species of lupine is common in chaparral and foothill woodlands throughout California, where it can grow to a shrub of 6 feet and closer to green in color, but here in the sandhills it stays lower and more compact (no more than 2 feet tall), its tight leaves with a shiny hue like a bright new coin. The fragrant everlasting rises like a white lock of wool to a height of 2 feet, its leaves linear in basal tufts with an aroma like minty pineapple; deployed in the garden or planned landscape, everlasting can be useful as edging along paths or to define the boundaries of a planted flower bed.

Isolated ecosystems like Bonny Doon serve as Darwinistic laboratories, where plants have evolved into micro-populations genetically distinct from their more widespread cousins. This may explain the number of silver-leafed endemic species restricted to such a narrow range, and also the several "undescribed species" like the tipless tidy tips (Layia platyglossa), the slender gilia (Gilia tenuiflora), and the Zayante everlasting (Gnaphalium sp. nov.) that demonstrate evolution in progress and warrant further taxonomic research. But the Santa Cruz sandhills also host several disjunct populations of plants that normally grow elsewhere -- closer to the ocean, for example, in the obvious case of mock heather (Ericameria ericoides), sea pink (Armeria maritima var. californica), and beach sagewort (Artemisia pycnocephala). It does stand to reason that such beach-loving species would thrive here in the sandy soils of an ancient seabed, but we may still wonder how they came to dwell here on a mountain so far from the shore. More perplexing is the presence of Ponderosa pine (Pinus ponderosa), a common tree in the Sierra above 3,000 feet but rather unusual this far west. Local botanist and revegetation specialist Valerie Haley explains that these pines were once considered their own distinct species, Pinus benthamiana, but later were lumped together with Pinus ponderosa -- although other botanists still argue whether or not to put them in their own subspecies. "These pines have 7 or 8 features that are different from those in the Sierra," says Haley, "but that's not always enough to convince the taxonomists."

Unbowed by the indignities of modern nomenclature, the flora of Bonny Doon exudes its own proud charisma, with a cool zeitgeist that endows this region with the sense of a silvery paradise regained. Local residents have pitched in with a volunteer program, organized by Haley, that meets once a month to clear trails, pick up litter, and otherwise support the underfunded and overworked Dept. of Fish & Game in maintaining the beauty of this rare and endangered preserve. Such relationships underscore the dividends generated by like-minded people who rally around the common goal of deepening our connections to earth. Whether at the beach, in the redwood forest, or some enchanted zone in between, native plants (and the people who cultivate them) help to define our special identity of place.

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Geoffrey Coffey propagates the Bonny Doon manzanita for Bay Natives nursery. He is the founder of Madroño landscape design studio and a freelance writer for the San Francisco Chronicle.

Distant rumblings from city hall portend a boom on Treasure Island, the former Navy base on the brink of becoming San Francisco's newest residential neighborhood. This exercise of urban planning in the middle of the bay will be a closely watched experiment. Early drafts of the master plan have called for sustainable design and green building development, for example, including an open space and landscaping component that emphasizes the use of locally native plants.

No plant is native to Treasure Island -- this 400-acre landmass was built of quarried rock and bay-dredged landfill in the late 1930s. But the first seawalls for that project were raised from the northern shoals of Yerba Buena Island, the natural island now joined with man-made Treasure Island like a siamese twin. And the steep slopes of Yerba Buena Island, though radically altered by invasive weeds and the hand of man, still harbor remnants of the original native flora, a population from which the landscape planners may wish to draw their inspiration.

Consider the coast red elderberry (Sambucus racemosa var. racemosa), enthusiastic seeder of moist forest margins, a proven survivor even in the deepening shadows of eucalyptus and monterey pine. This robust deciduous shrub can reach tree-like heights of 15-20 feet, filling the middle space beneath a taller canopy with a cheerful bloom of frothy white blossoms from March through July. Just now the fruit has begun to form, dramatic clusters of scarlet berries adored by birds. After the leaves drop in late fall, the bare elderberry still holds interest for its branches, which have a large pith and are easily hollowed out. The Ohlone used these twigs for flutes, whistles, and clapper sticks (a drum alternative); indeed, the genus name Sambucus pays homage to the Greek sambuke, a musical instrument made from elder wood. Excellent as a specimen plant in the garden or as a focal point in an urban park, and a tasteful alternative to cotoneaster, the coast red elderberry should rank high on anybody's landscaping wish list.