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Oh, my aching muscles...

In Praise of Our Western Palette

By Sean Hogan

Hundreds of drop-dead gorgeous plants native to the West—that will thrive in our gardens—are available with only a little searching. Recently there has been a renewed interest in natives, given concerns about water use and an inclination to tread more lightly on our planet. We gardeners can have the best of both worlds: feeding our gluttonous desire for beautiful plants—and honoring the environment.

The following are a few native groundcovers and low-growing shrubs to consider. First, the smallest.

Perennials & Groundcovers

Oxalis oreganum is a favorite seen in many old gardens—though some forms are feared as spreaders. This little “clover” is wonderful for massing among shrubs and trees. I prefer the evergreen forms from the coast, particularly two favorites. The first, Oxalis oreganum f. smalliana, which I received from Portland’s Leach Botanical Garden, is six inches in height with silver-splashed leaves and large pink flowers. The other, I found on the southern Oregon coast, and is named Oxalis oreganum ‘Klamath Ruby’. It grows eight inches tall, the leaves have a burgundy reverse, and it produces white to pale pink flowers. Both are perfect in the deepest shade, often growing through winter and able to take long periods of summer drought—only wilting in the heat of the Willamette Valley.

Pacific coast iris are regaining a foothold in local gardens now that their needs are better understood. Like other natives, they prefer pretty lousy soil, perfectly gritty (though clay works), and little summer water especially when heat is involved. They are divided in late fall when the season’s roots are beginning to emerge. Iris tenax, a native from southwestern Washington through the Willamette Valley is often seen in shades of purple, pink, and white. It is the only species to be partially deciduous.

Others, like Iris innominata of the Siskiyous, often bring shades of yellow and orange into the mix. Iris douglasiana, found from the central Oregon coast southwards in clumps to three feet tall, has substantial evergreen leaves and blue to white flowers from March to June depending on its location.

Asarum, or wild gingers, are not as numerous in western North America as in Asia but the few we have are both beautiful and vigorous. Asarum caudatum, with its heart-shaped, evergreen leaves is useful in dry shade, spreading in time to large ginger-scented patches.

Asarum hartwegii, another Siskiyou resident, grows in shade and—surprisingly—in sunny, inhospitable places, offering a color and texture as close as we can get to cyclamen. Its heart-shaped, silver-streaked leaves sometimes take on a reddish cast in winter. The flowers are black and held on the ground to be pollinated by crawly things. Slow to spread into compact clumps, A. hartwegii should be divided every few years.

The Shrubby Natives

More and more manzanitas are becoming available. One in particular has been outstanding in my garden: Arctostaphylos pajaroensis, endemic to a small area between Monterrey and Santa Cruz. It grows to three or four feet tall and is one of the most attractive winter-flowering plants available. Its open habit displays cherry red stems with peeling bark around which are clasping, eucalyptus-like blue-green leaves often flushed pink with spring’s new growth. The cultivar A. p. ‘Warren Roberts’ bursts out in midwinter flowers of a cheery pink.

A number of my favorite low shrubs are in the genus Ceanothus. Ceanothus gloriosus ‘Point Reyes’ is a native with gray-cast leaves. It has pale blue flowers on plants under a foot tall but spreading to four or five feet wide.

A somewhat daintier plant, the variety porrectus (C.g. var. porrectus) and specifically the cultivar ‘Emily Brown’ grows to 18 inches tall as a more rounded low shrub with small, dark green leaves and flowers the color of a blue June sky. A relative, C. rigidus and its cultivar ‘Snow Ball’ is only slightly larger with a clean white flower against silvery leaves in spring—wonderful with such neighbors as rosemary or a dwarf grevillea.

The small form of our coastal native C. thyrsiflorus var. repens, which remains under three feet in height, spreads gleefully over walls or stray basketballs hidden in the garden. It’s a little shy to flower, but when it does it’s covered in a solid amethyst-blue blanket offset by shiny one-inch leaves. In gardens where temperatures are likely to fall to 10 F or below, it should be used sparingly. Another great low-growing hybrid, Ceanothus x ‘Centennial’, is of about the same hardiness, remaining under 18 inches in height but spreading—well—pretty much forever. It has curled, shiny leaves and deep blue flowers. It’s my favorite ground covering ceanothus. I have it planted where Amaryllis belladonna emerges through it in late summer.

Our native coyote bush, Baccharis pilularis, found in various forms from Astoria to Baja and inland in places in the Willamette and Sacramento Valleys, ranges from large shrubs to petite groundcovers. The cultivar ‘Twin Peaks’ has small leaves and grows slowly to two feet, spreading to around five feet. One of my selections, ‘Creeping Green’, found on the central Oregon coast, reaches three by five feet. It produces creamy yellow flowers in winter and again in early summer, a draw for needy pollinators.

The buckbrushes, or Rhamnus, come in several small forms, including Rhamnus californica. New on the scene, and given to me by Rancho Santa Ana Botanical garden, is R. californica ‘Leatherleaf’. It has a nearly black-green appearance and, so far at least, a height of less than three to four feet. (If I’m wrong, please get back to me.)

There seems to be great fear of the Oregon grape, Mahonia aquifolium, possibly because of its overuse in highway medians where it never looks happy.But other species are well worth growing. Mahonia nervosa is used as a delicate, 18-inch groundcover. Another I’m quite enamored with is M. dictyota with blue-green leaves, a dense rounded habit to three or four feet, and extreme drought tolerance. Its early spring flowers, emerge from peach-hued buds. One word of warning: it’s a bit vicious as each “lobe” is armed with a spine.

These are just a few examples of low-growing natives that are an asset to any Northwest garden. Some are increasingly available at nurseries, including the California lilacs (Ceanothus). A visit to regional botanical gardens or nurseries will turn up some of the above. The next time you encounter one of these attractive and practical plants, take it home with you! NWGN

Sean Hogan collects drought-tolerant plants for his nursery, Cistus Design Nursery, in Sauvie Island, Oregon, www.cistus.com

pacificcoastiris.jpg
Pacific Coast Iris

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