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Dwarf Conifers

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Oh, my aching muscles...

Small Trees Play a Big Role

coenosium.jpg
The Coenosium Rock Garden at S. Seattle Community College

By Deborah Horn

Conifers once ruled the world. Long before the first magnolia opened a shy bud to a passing pollinator, conifers covered much of the globe. They still rule in the Northwest, where our cloudy winters favor the low-wattage, year-round photosynthesizing style of our beloved evergreens.

As slow-growing versions of the mighty conifers we see all around us, dwarf cultivars can create a distinctive Northwest feeling within the confines of a small garden or even a balcony container. These small trees bestow big benefits, as they are long-lived, low-maintenance and can provide food and shelter for wildlife.

Dwarfs Defined

There is some flexibility in the usage of the term “dwarf.” The designation generally applies to a conifer that grows two to ten inches a year. Yet dwarf conifers can range in size from tight sea urchin-like buns that only grow an inch or two a year to a scaled-down version of the coast redwood, which—while reaching only 20 feet rather than 320 feet—is not what most people think of as a dwarf.

Some of you may have experienced the “dwarf” that (ever so slowly) outgrew your original plans for a space. This is because the term dwarf often applies to a tree’s rate of growth, not its eventual size. For this reason, it is important to consider what the eventual size might be. If the smallest of the small is just right for you, look for dwarfs categorized as “miniature,” which means they only grow one to two inches a year.

Many of our classic dwarf and miniature conifers come from “witches brooms.” Witches brooms are clusters of abnormal foliage that are found on the branch of a normal tree. These growths are caused by genetic mutation, and may be propagated to retain miniature (or other) features. Other times, dwarfs are simply individuals which are genetic variants of normal species.

Designing with Dwarf Conifers

There are at least three Northwest garden styles where dwarf conifers can play a key role: Asian, alpine, and Northwest native.

Japanese and Chinese gardens have showcased dwarf conifers for centuries. If the twisted, wind-swept look of a pine is what makes the garden feel Asian to you, then a variety of the Japanese white pine (Pinus parviflora) may be the best choice. ‘Glauca Nana’ grows six to ten inches/year and will reach five to eight feet in ten years. Rod Parke, who tends a dwarf conifer garden in north Seattle, has a variety called ‘Koru’ which he says grows “very, very slowly.” One often used for bonsai because it has wonderful, corky bark and a dense blue pyramid shape is P. Parviflora ‘Miyajima.’

The dwarf forms of the Japanese Black Pine (Pinus thunbergii) have a fuller, compact look when compared to the Japanese white pine, and certain cultivars, such as Pinus thunbergii ‘Thundercloud’ have stunning white candles (new growth). ‘Koto buki’ is a smaller version of this much-admired dwarf. It has an upright shape, deep green (shorter) needles, and fat white candles—all in a package that grows six inches or less a year.

The Hinoki cypress, Chamaecyparis obtusa, with its deep green, scalloped fans, has dozens of diminutive cultivars from which to choose. The dwarf variety ‘Verdoni’ sports bronze/white/yellow highlights on a loose, open cone shape to six feet in ten years. A stunning group of them grows at South Seattle Community College’s Coenosium Rock Garden. The cultivar ‘Mariesii’ is similar, but grows to only half that size.

Naturally, dwarf conifers (specifically, the miniatures) are right at home in the alpine garden. Here we have gardens that aim to capture the spirit of those high, rocky places. Trees in the shape of cushions, buns and globes charm us the way only miniatures do—we can’t believe a tree can be so tiny!

Perfect for stone troughs and small rock gardens, Chamaecyparis obtusa ‘Golden Sprite’ grows only one-half inch per year. Pinus leucodermis ‘Smidt’ has densely packed pine foliage and grows to only two feet tall in 20 years. Rod recommends the miniature Mugo Pine ‘Jacobsen’ which in his garden has grown only a couple of inches in a decade. Perhaps a few of us (including myself) have mistakenly planted the straight species, thinking it was a dwarf. Big mistake.

Wherever cushion plants dwell among the gravel or scree, vertical conifers can provide structural contrast with columns of bright green (Chamaecyparis lawsoniana ‘Ellwood’s Gold Pillar’), sage green (Cupressus sempervirens ‘Totem’), or gold (Juniperus communis ‘Gold Cone’).  A favorite of Rod’s is the lacy, dark green, spiraling form of Thuja occidentalis ‘Degroot’s Spire’. This narrow column can reach ten feet, eventually.

Alpine gardens can also be Northwest native gardens, and there are a few excellent dwarfs that come from native stock.  The Kruckeberg Botanic Garden is home to a 40-year-old miniature tree that is just two feet across: Abies lasiocarpa ‘Du Flon.’  This variety was found by friends of the Kruckebergs, Bita and Alton DuFlon, as a seedling subalpine fir on the Olympic Peninsula.

For those of us who want to create native gardens in a limited space, even the shore pine, Pinus contorta var contorta, which eventually reaches 20 to 30 feet, might be too tall. Luckily for pine lovers (which include chickadees and finches) there are some truly amazing dwarf forms of our natives.  Pinus contorta ‘Spaans Dwarf’ grow three feet tall by four feet wide in ten years, with short, dense needles on a windswept branching pattern. If it is gold that you seek, look no further than Pinus contorta var latifolia ‘Chief Joseph’. It is a medium green in summer, but in winter—just when we need it the most—this one turns a brilliant gold that reminds me of the elusive gold of our alpine larch (Larix layallii), which, unfortunately, won’t grow in captivity.

Caring for Dwarf Conifers

It is important to provide dwarf conifers with proper conditions. Good drainage is usually required, especially for members of the chamaecyparis (false cypress) clan such as C. lawsoniana. Never place a soaker hose directly above the root ball of a chamaecyparis—you’d just be asking for trouble. Few dwarf conifers are actually drought tolerant, though most like sun. For a low-water-use area Rod suggests Pines and, “any tree with glaucous foliage, because the blue color is actually a waxy coating that prevents moisture loss.” He suggests yews, hemlocks and cryptomerias for part shade, but would never consign any conifer to total shade, not even the hemlocks.

By doing a little research beforehand, and selecting the best cultivar for your garden situation, you will find how much a little tree can contribute to the big picture.

Educational Gardens

If you’d like to adopt one of these enchanting trees, you can “shop” for just the right dwarf by visiting gardens that feature them before you actually buy. There are a  number of places to view dwarf conifers.

South Seattle Community College Arboretum/Coenosium Rock Garden, Seattle, Washington. The garden, on the SSCC campus, is open to the public. Its purpose is to “showcase many of the better dwarf conifers that are available from specialty nurseries and are little known to the public.” SSCC is located at 6000 16th Ave. SW, Seattle, WA 98106, phone 206-764-5300. The SSCC arboretum web site is: www.southseattle.edu/arboretum/

Conifer Display Garden at The Oregon Garden. This destination garden’s conifer display possesses one of the largest collections of dwarf and miniature conifers in the country. It was developed in partnership with the American Conifer Society, Western Chapter. The Oregon Garden is at 879 W. Main St., Silverton, OR 97381, phone 503-874-8100.

Kruckeberg Botanic Garden – Shoreline, Washington. Beneath a mature overstory of conifers, island beds containing dwarf conifers and native plants are interspersed over four acres. MsK Rare Plant Nursery is also located on the property. Free self-guided tours during open hours; guided tours are available. KBG is at 20312 15th Ave. NW, Seattle, WA 98160, phone: 206-542-4777.

Bellevue Botanical Garden. The Bellevue Botanical Garden in Bellevue, Washington has an alpine rock garden that features diminutive evergreens and allies. It is located at 12001 Main St., Bellevue, WA 98005, phone: 425-452-2750.

If you have a favorite dwarf conifer resource, e-mail us at norwesgard@earthlink.net and we’ll share it with readers on our web site. NWGN

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