Necessary Natives

My husband and I recently moved to a new house, and one goal I have for our new garden is to plant a sizable chunk of it with native shrubs and grasses. I look forward to planting vine maple, red flowering currant and mock orange, and perhaps ocean spray or Pacific ninebark. But all these shrubs are deciduous, and I would like some smallish evergreens as well, to keep things interesting in winter. Oregon grape is an obvious candidate, for wildlife value and its assertive leaves. There are already one or two plants of tall Oregon grape (Berberis aquifolium), and a little bit of shade where I can plant long leaf Oregon grape (Berberis nervosa). I’ve just planted my favorite, compact form of tall Oregon grape on a sunny corner, where it will develop great winter color. What else?

At first glance it may seems that, conifers aside, native evergreen shrubs are a little thin on the ground. But I am not going to be a purist about this native business, if that means limiting myself to species found right here in the Southern Willamette Valley. That’s just too strict for my gardener’s heart to contemplate. But if you interpret ‘native’ as indigenous not only to the Willamette Valley but to all of Western Oregon the list of plausible evergreens grows quite long and various. Local nurseries have long sold Oregon wax myrtle and kinnickinnick, which are not valley natives. Including other species from the coast and from the mountains provides the wonderful evergreen huckleberry (Vaccinium ovatum), native rhododendron (Rhododendron macrophyllum), coast silk tassel (Garrya elliptica) and even, for those of us with some very free draining soil, manzanita.

Hairy Manzanita (Arctostaphylos columbiana) does belong in the valley, according to my references, but we don’t see it often. There are other less familiar valley and foothill natives, such as buckbrush (Ceonothus cuneatus), an evergreen ceonothus that can grow to 8 feet. Two smaller plants in this category that particularly interest me are coyote brush and Oregon boxwood. Sun-loving coyote brush (Baccharis pilularis) has small, silvery green leaves and fall flowers that are attractive to insects. Deer do not seem to eat it. At four to eight feet this is not always a small shrub, but it seems to tolerate considerable pruning, and the leaf color is appealing. It’s not a common plant in nurseries, but Fern Hill Nursery in Cottage Grove sells it. I’m thinking of making a coyote brush hedge.

Oregon boxwood (Pachistima myrsinites), also called mountain lover (and sometimes spelled paxistima), is common in the mountains and occasional in the foothills. It has little dark green leaves and a dainty way of growing. Last spring I noticed it teaming up with beargrass, right at the edge of the cliff above Tamolitch Pool on the McKenzie River. They made a lively combination that I hope to reproduce just as soon as I can provide a gritty slope in light shade. Oregon box is not always easy to please, but it is well worth trying if you want a native, shade-loving low-growing evergreen (1 to 3 feet). Unfortunately it is difficult to find. ForestFarm in Williams, Oregon lists it but is currently out of stock.

EW November 2009

Late Summer Blues

The last weeks of summer feature three of my favorite blue-flowered plants: a perennial, a sub-shrub and a potentially large bush. Besides their lavender blue flowers and a late blooming time, they have several things in common. All three appreciate good drainage and lots of sunshine, are loved by butterflies and are pretty much deer-resistant. Although they are easy to grow in ordinary garden conditions, they are relatively drought tolerant and adapt well to low-water landscapes.

Anise hyssop (Agastache foeniculum) is a tough perennial in the mint family, native to the prairie states of North America. You can get it from nurseries that specialize in prairie plants but it’s somewhat easier, these days, to find ‘Blue Fortune’, a hybrid between anise hyssop and a similar plant from Asia named Agastache rugosa. Both anise hyssop and ‘Blue Fortune’ grow 2-4 feet tall, and do best in full sun in dryish, well drained soil. Their slowly lengthening, cylindrical spikes are packed with small flowers that open over a long season and look great with rudbeckia, echinacea, tall sedum and grasses. They are hardier than the agastaches called hummingbird mint, which can have trouble with our wet winters.

Blue mist shrub (Caryopteris x clandonensis), also known as bluebeard or blue spiraea, is a small Asian shrub with fragrant grey-green leaves that blooms on new wood. In cold climates, the topgrowth dies back in winter. Even in mild climates it looks best if cut back in spring. Pruning by one half or more as the buds break keeps it tidy and vigorous. Small flowers are produced over a long period along the top few inches of new growth. Two varieties popular for their strong flower color are ‘Longwood Blue’ and ‘Dark Knight’. Both are rather upright plants that can reach 4 feet.

My favorite caryopteris is ‘Heavenly Blue’. It has powder blue flowers and an excellently neat, mounding habit but it has become very difficult to find. I recently read about a new variety with deeper colored flowers named ‘First Choice’. It is said to grow 2-3 feet tall (after pruning) and may turn out to be an acceptable substitute for ‘Heavenly Blue’. Another low-growing variety is ‘Worcester Gold’, named for its yellow foliage. All these compact varieties look best where they are not crowded in by other plants and can show off their shapely hummocks. They look great in gravel gardens with rocks, small grasses and strongly architectural plants such as yucca and New Zealand flax.

And now the big one. Chastetree (Vitex agnus-castus) is an aromatic shrub from the Mediterranean. Like caryopteris it blooms on new growth, and can be pruned quite hard in spring if you need to restrict it growth. In this climate, it is more often grown with minimal pruning as a large bush or small tree and can eventually reach 10 - 15 feet. Vitex leafs out quite late in spring and quickly produces new shoots clad with attractive three-part leaves. Each shoot terminates in a densely packed, tapering pyramid of bloom. Vitex extracts have been used since ancient times to regulate the menstrual cycle and promote female fertility. I just know that pollinators love the flowers of this late bloomer, and our voracious deer have never bothered it.

Back to Nature

This past Mothers Day, at least 500 people attended Eugene’s first native plant garden tour. Organized by the Native Gardening Awareness Program (NGAP, a committee of the Emerald Chapter Native Plant Society of Oregon) the tour gave native plant enthusiasts and curious gardeners an opportunity to visit four public and eight private gardens where native plants play an important role. The private gardens varied greatly in age, setting, style and strategy, making for an interesting tour.

Aryana Ferguson and Bart Johnson’s yard adjoining Tugman Park is about 80% native and relatively mature: the formative “big push” came in 2003. Now salamanders make a home here, hummingbirds abound, chickadees and flickers squabble over who will nest in a snag and a hairstreak butterfly has laid eggs on the checker mallow. The day of the tour, the sunny front yard was ablaze with a pink froth of annual rosy plectritis intermingled with native buttercups, all busy with insect pollinators. I returned at the end of June to talk with the owners about their garden and the makeover experience, and was greeted by a whole new crop of flowers.

These people are pros. Ferguson has worked in resource management for 19 years and currently owns Madrona Consulting, working as project manager for a variety of restoration projects. Johnson, a professor at the University of Oregon, is an ecologist and landscape architect who works to merge ecological function with form and beauty. We talked on a deck overlooking the back yard, where they’ve kept a number of mature non-native plants – trees, mostly, and a few shrubs, which contribute both shade and structure.

When I toured this garden in May I was struck by its use of sedges and grasses, so prevalent in nature but often omitted from native gardens. A central feature of the back yard is a swale designed to take runoff from the roof. Sedges flourish here. Slough sedge (Carex obnupta) seems to be the most satisfactory – it likes semi-shade and stands up well. Uphill from the slough, in dappled shade, is a soft, bluish green lawn consisting mostly of Roemer’s fescue. “We mow every two weeks to keep the fescue from shading itself out” said Johnson, “ and we have to weed out exotic forbs and grasses.” Still, he’s surprised how little work it’s been.

As we toured the garden, Ferguson indicated a taller grass: “California fescue is a good bunch grass, especially in winter, when it looks really pretty,” she said. Johnson commented on big chunks of log scattered here and there among the plantings. “Put out some large wood out for salamanders and snakes. They love it.” We passed a sizable patch of camas (“it seeded in here on its own”) prompting the comment that camas is one of the easier plants to grow. Once it dies down you can mulch over it. Oregon iris is another winner. It is easy to weed around the clumps and, unlike camas, it stays green all summer.

Although their own garden was a radical makeover, Ferguson and Johnson now advise people to start small. “Don’t try to convert everything to natives all at once,” Johnson suggested. “Start from less diversity and add more as you can handle it,” he said, “and plant clumping things you can mulch around, he emphasizes. “The easiest native garden to manage is one of shrubs, sedges and ferns, in shade.” You can’t mulch prairie because you want things to self sow, so weeds are a bigger problem. Establish patches of easy perennials first, and mulch to reduce weeding. Fill in with annuals later.

In their sunny front yard, the couple removed weed cloth, bark mulch and the standard issue landscape shrubs, then sheet mulched with cardboard and two inches of mycorrhizal soil from Lane Forest Products to get a fresh start. Now a mix of prairie species with some from bright woodland, this area is still a work in progress. “We began by throwing out a lot of seed to create high diversity mixes of species,” said Ferguson, “and it didn’t work. We redid it with an effort at an aesthetic people are more used to.” Grasses are allowed only in clumps; perennial forbs are corralled in well-defined groups. “Each year we bring a little more order to it,” she said.

EW July 2009

Scent of the Rogue

One of the highlights of a raft trip down the Rogue River a few years ago was the glorious sight and scent of native azaleas that covered some stretches of the river bank. The azalea was Rhododendron occidentale, a deciduous shrub that occurs in a coast-hugging strip from Santa Cruz county, California to Coos County, Oregon, from sea level to 9000 feet.

Western azalea is one of only three native rhododendron species that are found west of the Rocky Mountains. Pacific rhododendron (Rhododendron macrophyllum) is the most familiar. This big evergreen is plentiful in the coastal forests of Oregon and Washington and on the western slope of the Cascades. It is easy to grow and makes a nice addition to irrigated gardens. Cascade azalea (Rhododendron albiflorum), is hard to cultivate and seems scarce even in its native habitat. I’ve hiked the Cascades for years and have seen it only a handful of times.

The gem among our three rhododendron species is Western azalea. Like many wild plants it is highly variable, growing from three to 15 feet in height and occasionally more. The flowers are generally white with a yellow blotch inside, but they are often tinged with pink or even red, and range in size from a little over an inch across to nearly four inches. This fabulously fragrant shrub has tempted hybridizers for 150 years, primarily in Europe, contributing its perfume to the famous Exbury line of deciduous azaleas and to hybrids such as ‘Irene Koster’.

Over the last century, here in the Northwest, a handful of collectors catalogued, selected and distributed some particularly fine forms of the species itself. Today these plants are relatively hard to find in nurseries, but Greer Gardens lists several varieties.
I have two plants I bought as babies from local plant sales. About ten years on, they are less than three feet high, with modest but shapely flowers just shy of an inch and a half across. One has particularly colorful buds, with a strong pink flush and a distinct line of color along the outside of each petal. This is a striking occidentale feature that comes through in ‘Irene Koster’.

It’s a thrill to encounter Western azalea along the Rogue or in the Siskiyous. It is pretty darn nice in the garden, too, blooming quite late in the rhododendron season when most deciduous azaleas are over. Wild inland and mountain populations grow near streams, rivers and springs, indicating a liking for moisture. But it tolerates periods of dryness between waterings in summer, especially with some shade. It also tolerates soggy soil in winter, and the leaves seem to be less susceptible to the powdery mildew that often disfigures other deciduous azaleas by late summer.

What is an azalea, anyway? Botanically speaking, all azaleas are rhododendrons, so what justifies calling them by another name? There are a number of features that separate azaleas from rhodies, although none seems to be completely reliable. The easiest to grasp is the number of stamens per flower: five in azaleas (occasionally six to ten), and ten or more in rhododendrons. This works most of the time. Interestingly, the Cascade azalea I mentioned earlier is sometimes called ‘white rhododendron’. How many stamens does it have? Ten.

EW June 2009

BUZZ BUZZ BUZZ

Lots of people are keeping honeybees these days. That seems like a good idea, since wild honeybees have more or less disappeared. Keeping bees increases the bee population generally and provides pollinators for your own garden (and the possibility of your own honey).

Like most people, I am alarmed by colony collapse disorder, mites and the decline in honeybees. After all, much of the food we eat is dependant, directly or indirectly, on honeybees. Conventional mass production of tree fruit and almonds would be almost impossible without this colony-dwelling bee that can be driven about the country in hefty numbers and put to work wherever bees are needed to pollinate enormous monocultures. No wonder honeybees are stressed out.

Unlike a Central Valley almond grower, however, the average home gardener should be able to get by without the honeybee, which is not native. A healthy population of native pollinators could probably do the job. There are thousands of native bee species in the US, not to mention other types of pollinating insect. Sadly, many of the same factors that hit honeybees affect native bees as well. In fact pollinators of all kinds are disappearing.

One element behind this decline is undoubtedly the loss of pollinator-friendly habitat, through development, conventional agriculture and widespread pesticide application. Native bees are affected too; they are also becoming infected with diseases and parasites spread by honeybees. All the same, non-honeybees out-number honeybees in my garden. Bumblebees have been particularly conspicuous.

Like honeybees, bumblebees are social insects, forming small colonies. Other kinds of native bees (mason bees, for example) are solitary; that is, individual bees don’t interact with one another. There may be many about at the same time, but they don’t cooperate.
The value of native bees in agriculture is beginning to get some attention. Bumblebees, it seems, venture out at lower temperatures than honeybees and even tolerate a bit of rain - valuable traits if you have early-flowering crops to pollinate. And all native bees, adapted to their work by coevolving with the plants they pollinate, can be as much as 100 times as efficient at it.

While many native bees are specialists, visiting only a certain kind of flower, bumblebees and some others are ‘generalists’ that are happy to visit your apples, squash and so on. What can we do to encourage them? Solitary bees lay their eggs in bark crevices and hollow stems, and occasionally in man-made, purpose-built accommodations. Some bees need a certain amount of bare, uncultivated ground (without a thick covering of bark mulch!). Bumblebees nest in cavities in the ground, or beneath planks or inverted plant pots.

Slightly untidy gardens may have the edge here. Pesticides are out of the question, needless cultivation should be avoided, debris piles and weed patches are great. When it come to nectar sources, many of the plants that attract the honeybee also attract native generalists. Lavender and oregano, both from the Mediterranean, are magnets to both. Native plants, however, have been shown to support a larger and more diverse population of native insects, including bees. A quick internet search on ‘plants for pollinators Oregon’ will yield a wealth of information.

EW May 2009

Trout, Fawns and Dog's Teeth

I first encountered Oregon fawnlilies (Erythronium oregonum) in the yards of older homes in Eugene’s rocky south west hills, where I lived at the time. Sturdy little relics of pre-development days, they still grow there in the thin grass under native oaks and widely spaced Douglas firs. These cream colored, down-facing ‘lilies’ on stems less than a foot high flourish in open woodland throughout the Willamette Valley and elsewhere west of the Cascade mountains, blooming in late March and April.

Erythronium species occur naturally in Asia, Europe and North America. Most of them, around 20 species, are found in Western North America. Dog’s tooth violet, adder’s tongue and troutlily are all common names for various erythroniums, but those in the American west are generally called fawnlilies. The first name refers to the oddly shaped, elongated bulb, while troutlily and fawnlily reflect the brownish spots or mottling on the leaves of some species, including Oregon fawnlily.

Much less common in our area than Oregon fawnlily is the pink coast fawnlily (Erythronium revolutum). It grows in meadows and damp forests close to the coast, from northern California to the Olympics. The leaves sport a network of silvery white or brownish veins. You can see coast fawnlilies in the rhododendron garden at Hendricks Park in Eugene, where it was introduced many years ago. The splendid white-flowered avalanche lily (E. montanum), a species you may run into at higher elevations in the Coast Range and the Cascades, has plain green leaves.

Avalanche lily is reputedly difficult to grow, but some species of erythronium do really well in gardens. Oregon fawnlily spreads by seed and stolons and may form wide-spreading colonies in a well-drained, woodsy area that gets some sun in spring. (All species go dormant after they set seed.) In more conventional flower gardens it may be easier to find a home for the kinds that readily make bulb offsets and form clumps. These include the beautiful European dog’s-tooth violet (Erythronium dens-canis), but I have had difficulty getting this established in my garden.

I’ve been more successful with coast fawnlily and two robust, well-tested garden varieties, Erythronium californicum ‘White Beauty’ and E. ‘Pagoda’, a cross between ‘White Beauty’ and the yellow-flowered, plain green-leafed E. tuolumnense. You can grow these in ordinary good (not too heavy) garden soil between small shrubs and other clump-forming perennials. They will tolerate moderate summer watering as long as the soil is well-drained. It is a good idea to mark the clumps so you won’t disturb them during their long summer dormancy and so that you can keep vigorous, self-sown plants like foxglove and columbine from gobbling them up.

Common Oregon fawn lily can be grown from seed. You can also buy bulbs, from late summer into fall, from Buggy Crazy at the Lane County Farmers’ Market. Sometimes Buggy Crazy has other species, too. Plant sales are another good source: watch for sales, coming up in spring, sponsored by Destination Imagination, Mt. Pisgah Arboretum, Avid Gardeners and the Willamette Valley Hardy Plant Group. Go early.

EW April 2009

Tails of Glory

The British have always had an eye for a good plant, and anything that looks alluring in a gloomy northern winter should be downright irresistible. So it’s not surprising Brits embraced the Oregon native, coast silktassel bush (Garrya elliptica). Scottish explorer and plant hunter David Douglas introduced the plant to cultivation in 1828, along with salal and red-flowering currant, from seed he collected in the Pacific Northwest. Since it is the only member of the genus that is commonly encountered it is usually called silktassel or just garrya.

In London, where I spent this winter, silktassel is almost ubiquitous, yet I rarely see it in Oregon gardens. At the coast, where it grows naturally, it is happy as a clam. Given a little shade from the hottest sun and shelter from wind, it also does fine in the Willamette Valley. Why don’t we plant it more often? One reason may be that it can grow a little thin and gangly, and gardeners seem conditioned to expect evergreens to be dense and rounded. Unfortunately, many of the plants that fill that bill grow too big, too fast. Some, such as cherry laurel and Portugal laurel, are also highly invasive. In the right situation, silktassel may be a good alternative.

What’s so great about silktassel is its catkins. Most of the year it is just an unexceptional evergreen, whose dark green, leathery leaves with wavy margins and palely felted undersides are not quite distinctive enough to get your attention. But from December through February, when it shakes out those beguiling, gray-green tassels, a good specimen will stop you in your tracks. Female plants that have a male companion produce fruit that attract birds, but male plants are most often planted because they have longer, showier catkins. The American cultivar ‘James Roof’ has catkins a foot long.

Garrya grows at a moderate rate to 8-12 feet, in sun or shade. The leaves may burn in hot locations (don’t plant it against an unshaded south-facing wall) while in heavy shade the bush will be quite scrawny. You can minimize this effect by planting several young plants in a group two feet apart, shortening young growth occasionally to help maintain density. I’ve seen this done effectively in London parks. Alternatively, you can train your silktassel on a cool wall or fence. It’s young limbs are flexible, and an espalier is a wonderful way to show off the catkins. In a sunny place you can also train it as a small tree for maximum display.

A word of warning: silktassel does not recover well after transplanting, nor does it like to be cut way back (as in renewal pruning). So you want to get it in the right place early on and prune it, where necessary, lightly and often. Like many Oregon natives, silktassel is tolerant of drought. It also puts up with pollution, and does not appear to be fussy about soil type. It does, however, need good drainage, especially where it grows in heavy soil. Plant it slightly above grade, and be sparing with summer water. If it grows quickly but is slow to flower, the soil may be too fertile.

EW March 2009