Arctostaphylos for Pacific Northwest Gardens

By: Paul Bonine
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Xera Plants

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Paul Bonine is a garden writer, lecturer, and owner of the wholesale specialty plant nursery Xera Plants, in Portland, Oregon….

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Hairy manzanita (Arctostaphylos columbiana) in habitat above the Columbia River. Photographs by Joshua McCullough, PhytoPhoto, except as noted - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Hairy manzanita (Arctostaphylos columbiana) in habitat above the Columbia River. Photographs by Joshua McCullough, PhytoPhoto, except as noted

No other shrub is more symbolic of the Pacific Coast than manzanita (Arctostaphylos). From British Columbia to Baja, one species to many are endemic from the beaches to the mountains. Comprising more than fifty species and dozens of cultivars, they are one of the most distinctive shrubs of the far West, familiar to campers and hikers but little known in Pacific Northwest gardens—beyond the ubiquitous groundcover kinnikinnick (A. uva-ursi ).

We have been cultivating a wide variety of shrubby manzanitas at our nursery in Oregon’s Willamette Valley, and have been delighted to see them capture the imagination of Northwest gardeners. Once thought of as finicky in our region, it turns out that many, including those native to California, are ideally adapted to our naturally dry summers, and are surprisingly tolerant of winter cold as well. In California—where the majority of species are native, and where a multitude of cultivars are readily found in nurseries and at plant sales—they have long been recognized as valuable garden shrubs and have gained a staunch following among native plant enthusiasts. What they offer to gardeners in the Pacific Northwest is another component in the movement towards low-maintenance and low-water gardens. Handsome evergreen shrubs, they combine picturesque bark, showy flowers (early in the season), and food for wildlife; they are useful as both specimens and transitional shrubs to meld with neighboring wild areas. Their distinctive bark and sinuous branching habit might even suggest a dwarf version of our beloved—and related—native madrone (Arbutus menziesii).

Arctostaphylos canescens subsp. sonomensis in a garden with Osmanthus and Cupressus macrocarpa ‘Wilma Goldcrest’ - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Arctostaphylos canescens subsp. sonomensis in a garden with Osmanthus and Cupressus macrocarpa ‘Wilma Goldcrest’

A Familiar Family

The genus Arctostaphylos is part of the large rhododendron family (Ericaceae). Their urn-shaped flowers resemble those of such related and common Northwest garden shrubs as Pieris and heaths (Erica and Calluna) as well as our native Vaccinium and Gaultheria. The upright, symmetrical leaves of manzanita are distinct among evergreen shrubs: rounded and waxy, many with a sharp apical tip, they are nearly always held perpendicular to the sun’s face, an adaptation that helps plants limit moisture loss during the West’s dry summers. The foliage comes in a fascinating array of colors, from felted gray and silver to sage and bright glossy green. On some, the new growth takes on dramatic tints of orange, coral, and red, adding to the appeal of the plants.

From midwinter into spring, clusters of pink to white, urn-shaped flowers appear in profusion at the branch tips and persist for weeks in the cool air. Small rounded fruit follow and ripen by summer, often with a blush on one side. Resembling tiny apples, they were christened “manzanita” (little apples) by the Spaniards when they first visited California. The fruits range in color from rust orange to brown, red, and maroon. Though showy, they are often quickly consumed by birds and other wildlife, even in home gardens.

Its bark is the most spectacular feature of a manzanita. Smooth and muscular trunks and branches twist and turn with the illusion of motion. In most species, the thin bark buckles and splits, rolls up into ribbons, and then exfoliates in early summer; the new bark becomes darkened and streaked before achieving its final smooth texture by mid-summer. The hue varies from mahogany, deep maroon, or red to nearly black, and orange. Bold and strong, no other shrub can compete with the beauty of a manzanita’s trunk and bark.

Some Arctostaphylos species develop an enlarged area called a burl at soil level; new shoots emerge from the burl following fire or extreme drought, or from extensive pruning to rejuvenate a plant in the garden.

Summer fruits on hoary manzanita (Arctostaphylos canescens - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Summer fruits on hoary manzanita (Arctostaphylos canescens)

Native Northwesterners

Though the greatest diversity of Arctostaphylos species occurs in California’s chaparral country, nine (or more) species are native to Washington and Oregon. They range from tall shrubs to groundcovers and can be found in a variety of biomes. Some have gained a place in gardens, while others have yet to find mass acceptance, and still others have proven difficult to tame.

West of the Cascades, hairy manzanita (Arctostaphylos columbiana) is the most widespread species, ranging from the Northern California coast into southwestern British Columbia. It forms an upright to spreading shrub, to ten feet tall and as wide, with gray to sage green leaves; conspicuous hairs on the stems make it one of the easiest to identify. In April, pale pink to white flowers precede tawny orange fruits, which contrast with the glossy deep mahogany bark and stems. On the Oregon coast, hairy manzanita is common on stabilized sand dunes, where it mingles with shore pine (Pinus contorta), evergreen huckleberry (Vaccinium ovatum), and salal (Gaultheria shallon). Further inland, it appears sporadically in disturbed and exposed areas of the Coast Range and foothills of the Cascades, and even as far east as the central Columbia Gorge. The area north and west of Mt Hood is particularly rich with this species. In Washington, large populations occur on the drier eastern side of the Olympic Peninsula and are conspicuous from the Kitsap Peninsula north and west to Port Angeles. In spite of its wide natural range, hairy manzanita has proven to be an exacting garden plant. It shuns all irrigation and is subject to leaf spot diseases. Provided with fast draining soil and good air circulation, however, it makes a handsome shrub for transitional areas.

A ruggedly handsome specimen of whiteleaf manzanita (Arctostaphylos viscida) in southwestern Oregon - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

A ruggedly handsome specimen of whiteleaf manzanita (Arctostaphylos viscida) in southwestern Oregon

Kinnikinnick, or bear berry (Arctostaphylos uva-ursi), is a well-known denizen of Pacific Northwest landscapes. As a groundcover, it does dutiful work on slopes, tolerating both light irrigation and drought. In habitat in the Pacific Northwest, it can be found along sandy stretches in the coastal zone, on glacial moraine in the Puget Sound region, on pumice strata in the Cascades, and throughout the Siskiyou and Klamath ranges. Though it is found on fastdraining soils in its habitat, it is surprisingly adaptable to a variety of soils in cultivation, including clays (on sloping sites). Many selections have been made of this cold-hardy, ornamental plant. In our region, two of the best are ‘Vancouver Jade’, with sage green leaves, pink flowers, and a prostrate habit, and ‘Wood’s Red’, a low mound grown for its large red berries.

Where hairy manzanita and kinnikinnick grow in close proximity to each other, hybrid offspring, known as media manzanita (Arctostaphylos ×media) may appear. The product of an upright species and a prostrate species, media manzanita often shows a variation in habit: almost upright forms can be found, but the most commonly seen is decumbent with deep green, paddle-shaped leaves and light pink flowers in early spring. This hybrid is much more amenable to cultivation than hairy manzanita and may be used as a large-scale groundcover. We have introduced and named ‘Martha Ewan’, a particularly handsome selection with deep green foliage and a vigorous, mounding habit. It was found near Manzanita, Oregon (so named for the local abundance of hairy manzanita).

Kinnikinnick (Arctostaphylos uva-ursi) cascading over a garden wall - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Kinnikinnick (Arctostaphylos uvaursi) cascading over a garden wall

Another low, spreading species is pinemat manzanita (Arctostaphylos nevadensis), which is found in the Cascades, at higher elevations in the Olympics, and throughout the mountains of southern Oregon south into California. Aptly named, it forms an extensive understory beneath pines and firs in the middle elevations of the eastern crest of the Cascades, where it may be buried in snow for months. Pinemat manzanita assumes a more mounding habit than kinnikinnick, to which it is strikingly similar. The best way to differentiate between the two is by the shape of the leaves: kinnikinnick has distinctly rounded leaves, whereas leaves of pinemat manzanita have a pointed or mucronate tip. Both have deep green foliage with white-tinted, pink flowers, but the berries of pinemat manzanita take on more russet tones.

East of the Cascade Crest in Oregon and Washington, the glossy, grass green leaves of green leaf manzanita (Arctostaphylos patula) become a familiar sight, forming extensive stands, often under the canopy of large ponderosa pines. This species occupies vast tracts of land and has one of the largest natural ranges, stretching deep into the Rocky Mountain States and as far south as the higher elevations of Arizona. Clear pink flowers are showy in spring and are followed by dark maroon fruits. It is an upright species, with an average height of five feet and an equal spread. Its twisted trunk and stems become a vivid cinnamon orange—striking below the foliage and even more dramatic against a drift of pure white snow—a common sight in its range. On the west side of the Cascades, it seems to languish, preferring drier air and colder winters.

Flowers of Pajaro manzanita (Arctostaphylos pajaroensis), a coastal California species that has proven remarkably hardy in Oregon - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Flowers of Pajaro manzanita (Arctostaphylos pajaroensis), a coastal California species that has proven remarkably hardy in Oregon

California Extensions

A larger cluster of Arctostaphylos species occurs in southwestern Oregon’s Klamath and Siskiyou mountains, the northern continuation of the California Floristic Province. They may be found in mixed forests, open rocky areas, or in chaparral shrub communities. They may also inhabit specialized soils, such as the serpentine soils that occur throughout the area.

Hoary manzanita (Arctostaphylos canescens subsp. canescens) is a gray-leaved species that congregates in mixed forest margins as well as in open sites where it will grow in extensive pure stands. It is found as far north as Oregon’s Douglas and Coos counties and south into California, where its range is extensive. A fine coating of hairs on both sides gives the leaves a frosty gray appearance; they vary in size but nearly always terminate in a sharp tip. This is one of the earliest species to bloom in the Pacific Northwest, with white to pink flowers appearing in late February to March. It does not grow in serpentine soils. As a garden plant, it is unpredictable in growth and in its adaptation to garden conditions—surprising given its extensive range.

One of the least common species found in southwestern Oregon is Eastwood manzanita (Arctostaphylos glandulosa subsp. glandulosa), best identified by its glandular green leaves, stems, and pedicels. A burl-forming manzanita, it forms a dapper shrub to five feet tall and as wide, and is often found on disturbed sites on the coastal side of the Klamath and Coast ranges. In mid-spring, it is covered in pure white flowers, followed later by maroon berries. In California, Eastwood manzanita extends south along the coast for the full length of the state.

Howell’s manzanita (Arctostaphylos hispidula) ranges from the Coast Range in California as far north as Coos County, Oregon, with the most conspicuous stands of this tidy shrub seen along the Rogue River. Though it is similar to Eastwood manzanita, this species tolerates serpentine soils. Another burl-forming species, it has oblanceolate leaves that are medium green with fine hairs on both surfaces of the leaves. Twigs from the latest year’s growth are often maroon, which further assists in identification. Berries ripen to red and burgundy and have a more flattened appearance than on other species in Oregon.

Whiteleaf manzanita (Arctostaphylos viscida) is one of the most striking species in southwestern Oregon, distinctive for its large, round, smooth leaves of the palest gray, and for new growth that emerges a rubbery, startling red. In early spring, it bears white-tinted, pink flowers. Its trunk and stems are a smooth, deep mahogany brown. Non-pubescent stems and leaves, covered with a waxy white powder, make it one of the easiest to identify where it occurs in Jackson, Josephine, and Curry counties, and farther south into California. It is conspicuous as the sole gray- (or white-) leaved species to appear on serpentine soils. In the Kalmiopsis Botanical Wilderness, it mixes with western azalea (Rhododendron occidentalis) on vast serpentine hillsides, in a finely balanced community surrounding bogs filled with California pitcher plant (Darlingtonia californica). Though similar in appearance from a distance, hoary manzanita will not take the harsh conditions of serpentine soils; where serpentine soils abut other soil types, there may be an abrupt transition from a mix of species to pure whiteleaf manzanita.

All of these California species are currently recognized as occurring in southwestern Oregon, along with the hybrid and four species mentioned earlier. Often, several species will occur in close proximity, and natural hybridization may lead to intermediate forms scattered among them. Where Arctostaphylos viscida occurs on serpentine soil adjacent to A. canescens on non-serpentine soil, the hybrid A. ×cinerea can be found. Another hybrid, known as A. ×parvifolia, may occur in Oregon between A. glandulosa subsp. glandulosa and A. nevadensis. Other hybrids can occur in swarms where two or more species intersect. Add to that a natural variation of characteristics within each species, and you get a botanical puzzle that is difficult to unravel. Though frustrating to botanists, this tremendous diversity offers the potential for selection of cultivars in a myriad of shapes and sizes for Pacific Northwest gardens.

A young hedge of Arctostaphylos ‘Sunset’. Author’s photograph - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

A young hedge of Arctostaphylos ‘Sunset’. Author’s photograph

Culture

We began growing manzanitas in our nursery because they were seldom available commercially in the Pacific Northwest. Our experimental plantings, as well as occasional commercial plantings, had shown that they succeeded easily in our climate. During the severe freeze of 1989, when the temperature plunged to near 0° F (-18° C) in Eugene, plants of Arctostaphylos ‘Howard McMinn’ showed only superficial damage and recovered quickly—unlike many other more commonly grown shrubs. This gave us a clue that manzanitas were well adapted to our climate and could succeed where other exotic shrubs had failed. They require no supplemental irrigation to thrive, subsisting only on natural rainfall; there is none of the aesthetic decline suffered by many other shrubs native to summer rainfall regions.

We now grow more than fifteen different kinds, and have plans to add more if they show similar ease and adaptation in gardens. The paradigm of landscapes needing heavy irrigation during our naturally dry summer months has slowly been replaced by a new awareness of the importance of water conservation. Less irrigation—in fact, no summer irrigation—is what Arctostaphylos require to thrive in the Northwest.

Cultural requirements for Arctostaphylos in Pacific Northwest gardens are not difficult to meet but are specific: well-drained, unamended mineral soils, good air circulation, little or no summer irrigation, and no fertilizer. Manzanitas are adapted to well-drained soils but will tolerate clay soils on slopes, where there is no summer irrigation. In well-drained situations, some will accept occasional irrigation. Poorly drained sites, shade, and regular summer irrigation are to be avoided. This regime fits well into low-water and low-maintenance landscapes; in such situations, manzanitas combine easily with other plants native to mediterranean climates (winter wet/ summer dry).

We have found that manzanitas native to drier climates (eg, the many California species and cultivars) behave differently in our wetter climate. In western Oregon and Washington, our annual rainy season extends the growing season for these plants by several more months, compared to their natural habitat; that means that they often grow larger in our climate than they do in the wild.

To maintain good air circulation for Arctostaphylos in the Pacific Northwest, give them an open exposure with little crowding or competition from neighboring plants. This will help avoid leaf spot diseases that can occur in stagnant air. Mud splashed onto the leaves during heavy rainfall can result in a fungal leaf spot, especially on the lowest exposed branches. A coarse mulch around newly planted specimens will reduce the amount of mud splash.

Gardeners in the Pacific Northwest have been taught to amend their soils with compost to achieve maximum results in the garden. For manzanitas, however, as with many native plants, overly rich soils often result in too rapid growth, leaving plants vulnerable to wind rock and fungal root pathogens. Native soils with good drainage produce the best results.

Pruning Arctostaphylos is a more complex matter. New growth may be tip pruned lightly to encourage a denser, if temporarily, smaller plant. This may be done after new growth has commenced and before the next year’s flower buds have emerged. Older stems that have begun to shed bark will not resprout; these should be pruned thoughtfully to avoid permanent disfigurement. To increase air circulation and expose a manzanita’s network of smooth, sculptural trunks, removing the lower branches works well. The result transforms a mere shrub into a piece of living sculpture.

Unfortunately, gardeners smitten by the beauty of the larger manzanitas often want to fit them into spaces that are too small; such short-sighted placement usually results in pruning that destroys the natural form and grace of the plants. With the diversity found in the genus, there is plenty of opportunity to choose a manzanita that will fit the intended site. Choosing the right cultivar or species can eliminate the need to prune

The cold hardiness of Arctostaphylos species and cultivars from California has been a great surprise. During December 2008, we experienced our coldest spell in ten years. We observed the effects on all of the manzanitas that we grow and others that we were considering. Species and cultivars native to areas that we thought would pose hardiness issues in the Pacific Northwest performed astonishingly well; among them were Arctostaphylos rudis and Arctostaphylos pajaroensis, both native to the central California coast; there was little or no damage to any of the plants in the ground. Arctostaphylos ‘Austin Griffiths’ was in full bloom prior to that cold wave, when the temperature fell to 11° F (-12.5° C) and remained below freezing for two weeks. When the thaw came, we were astounded to find that the blossoms were unscathed and flowering continued unabated for another month. This cultivar and several others show great promise as valuable winter-blooming shrubs in our gardens.

Companions for Manzanitas

In my own garden, I have found a number of plants that combine well with the requirement for summer-dry conditions that manzanitas appreciate. An underplanting of California fescue (Festuca californica), which is native to the Willamette Valley south into the mountains of California, thrives as a natural understory component. Native species of Ceanothus that occur with Arctostaphylos in the wild are a natural choice; especially appropriate is buck brush (C. cuneatus), which occurs with manzanitas throughout southern Oregon. A number of drought-tolerant Southern Hemisphere shrubs, such as Ozothamnus rosmarinifolius, Grevillea juniperina, and Corokia cotoneaster, complement the familiar chaparral feel, echoing the fine billowing textures found in that plant community. More common landscape shrubs, such as drought-tolerant selections of heavenly bamboo (Nandina) and Pittosporum, have also worked well.

Many perennials thrive beneath manzanitas and have proven to be ideal companions. Erodium ×kolbianum ‘Natasha’ blooms for months with lavender blotched flowers, forming lacy clumps that require little water. Royal purple sage (Salvia muelleri) blooms almost as long; its shrubby form and deep purple flowers fill the niches between other plants, just as native sages do in habitat. Epilobium (syn. Zauschneria) septentrionalis ‘Select Mattole’ forms silver and vermilion pools beneath my Sonoma manzanita (Arctostaphylos canescens var. sonomensis) in late summer and early autumn. Other perennials that I’ve had success with are Scutellaria, Oenothera, and Penstemon, all of which require no supplemental water in summer and combine well with native bulbs such as Brodiaea and Dichelostemma.

One particularly harmonious winter combination that I have enjoyed for years has been a planting of Cyclamen coum beneath a large established ‘Howard McMinn’ manzanita. The cyclamen begin to bloom in late December and continue through early spring, coinciding with the flowering of the overhanging manzanita. The cyclamen’s handsome marbled leaves contrast with the mahogany bark and persist as a small scale groundcover through late spring, before going cleanly dormant for the summer.

Arctostaphylos densiflora ‘Howard McMinn’ in a garden setting. Author’s photograph - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Arctostaphylos densiflora ‘Howard McMinn’ in a garden setting. Author’s photograph

A Selection of the Best for the Northwest

Based upon our twelve-year experiment in growing manzanitas, here is a sample of the best cultivars for gardens west of the Cascades in the Pacific Northwest.

Arctostaphylos densiflora ‘Howard McMinn’ (Sunset zones 6-24; USDA zone 7b) One of the most popular and consistently grown manzanitas in the Northwest, this cultivar shows excellent garden tolerance and cold hardiness. Small, white-tinted, pink flowers appear profusely in March. Foliage is glossy green and handsome year round; bark is deep cinnamon mahogany. Tolerates summer water. At ten years, it can reach eight feet tall and wide.

Arctostaphylos ‘Sunset’ (Sunset zones 6-9,14-24; USDA zone 7b) This little-known jewel has become one of our favorite cultivars. Low and spreading, its new growth is tinted orange, before settling into a strong olive green. Flowers are white and appear in early spring. The five-year size is four feet tall and six feet wide. Tolerates clay soils and more pruning than other selections. An excellent landscape or garden shrub.

Arctostaphylos bakeri ‘Louis Edmonds’ (Sunset zones 4-9,14-24; USDA zone 7b) Consistently the best gray-leaved manzanita for gardens in the Northwest, it pairs attractive foliage with deep pink flowers in early spring, all set against ebony black bark. An upright habit, reaching five feet tall and four feet wide in ten years. Cold hardy; best with no summer water and well drained soil.

Arctostaphylos densiflora ‘Howard McMinn’ in a garden setting. Author’s photograph - See more at: http://www.pacifichorticulture.org/articles/arctostaphylos-for-pacific-northwest-gardens/#sthash.cFQDub9E.dpuf

Arctostaphylos densiflora ‘Howard McMinn’ in a garden setting. Author’s photograph

Arctostaphylos ‘Austin Griffiths’ (Sunset zones unknown, but estimated to be 4-9, 14-24; USDA zone 7a) Extremely adaptable and cold-hardy large shrub with big, sage green leaves and an upright habit—everything a manzanita needs for greatness. Bark is a deep mahogany brown. Large pink flowers open in December and continue to be effective through February. At eight years, height is twelve feet and width is eight feet.

Arctostaphylos x media ‘Martha Ewan’ (Sunset zones unknown, but estimated to be 4-9, 14-24; USDA zone 7a) Our introduction of an exceptionally good form of this natural hybrid found near Manzanita, on the northern Oregon coast. Deep green leaves are paddle shaped on a domeshaped, spreading shrub to three feet tall and five feet wide with white flowers. Shows excellent garden tolerance.

Arctostaphylos ‘Greensphere’ (Sunset zones unknown, but estimated to be 4-9, 14-24; USDA zone 7a) A perfect manzanita for a small garden, this extremely slow-growing selection will only attain two feet in height and three feet in width in eight years. In early spring, it covers itself in pearl pink flowers. Tolerant of cold, it appreciates good air circulation. Its bark is a handsome mahogany red.

We have begun to focus our search for manzanitas on those native to Oregon and Washington to increase the number of locally native selections. Surprisingly, many from Oregon and Washington do not have the ease of culture in both the nursery and home garden as do the many cultivars and species from California, but we will continue our search.

Arctostaphylos have shown a remarkable adaptation to our climate, soils, and, finally, garden-making. We have found a large and expanding variety of species and cultivars that thrive in our region. The enthusiasm that gardeners have shown for Arctostaphylos continues; we hope manzanitas of all kinds and sizes will become staples of low-water landscapes and find a permanent home in Pacific Northwest gardens.

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