NEW Trips to Take!

Myrtle's easy when the conditions are right.

 
 
 
 

NEW Plants to Try!

Louis tries to capture the exact words to describe the fleeting but deep pleasures to be found in these Summer-into-Autumn incredibles.

 
 
 
 

New Gardening to Do!

Allergic to bees? You can still have an exciting garden, full of flowers and color and wildlife.

 
 
 
 

A Gardening Journal

The Best Season Ever: Horsebalm

With shiny large leaves and carefully arrayed plumes of yellow flowers, horsebalm is a quiet beauty.

Collinsonia canadensis in bud 092015 320

Its many common names—citronella horsebalm, heal-all, richweed, stoneroot—suggest further abilities far beyond such pleasing visuals, too. Let me rave further!

Collinsonia canadensis in bud 092015 640 

 

With shiny large leaves and carefully arrayed plumes of yellow flowers, horsebalm is a quiet beauty. As each bud opens, a pair of long stamens thrust forward, like arms ready for an embrace. 

 

Collinsonia canadensis in flower details 092015 640 

 

For me, it's the geometry of the raceme that is the most intriguing. The overall pyramidal shape is formed from individual plumes of buds that are, themselves, pyramidal. Below the top, pairs of side stems bear the same pyramical plumes of buds. Lower rungs of the floral display have side branches of buds that are, you guessed it, also pyramidal. If only this plant were a thinking creature, I could compliment it on the creation of an elegant larger entity from a minimum of identical parts—for fractal ingenuity that is attractive, too.

 

Collinsonia canadensis fingers 092015 640

 

It's striking that the many common names of Collinsonia canadensis reference only non-visual capabilities: the supposedly healing power of horsebalm, the lemon fragrance of citronella, the general wellness of heal-all, the hard-to-grind toughness of stoneroot. For me, the health benefits of this unusual perennial arrive exclusively by eye, but they are no less appreciated.

 

 

Here's how to grow this handsome, understated perennial:

 

Latin Name

Collinsonia canadensis

Common Names

Many: Horsebalm, citronella horsebalm, stoneroot, richweed, hardhack, and heal-all do not exhaust the list.

Family

Lamiaceae, the mint family.

What kind of plant is it?

Hardy herbaceous perennial.

Hardiness

Zones 4 - 8.

Habit

Clumping. Despite this species' kinship to the aggressively-spreading mints in the Lamiaceae family, it shows no interest (in my garden at least) in similar unwanted wandering.

Rate of Growth

Steady.

Size in ten years

A clump two to five feet tall and two to three feet wide. I'll be transplanting my clump to sunnier and more-moist circumstances: After five years, it is vigorous and stays in good condition all season, but is just two feet tall and wide.

Texture

Solid but not heavy. The large foliage is just glossy enough, and widely-spaced enough, to remind you of that of Hydrangea macrophylla.

Grown for

its status as a bizarrely-underused but very handsome native:  By planting Collinsonia canadensis, you score points three ways: The species is understated and elegant, so burnishes your reputation for taste and discretion; it's native, so is by definition doing a favor to native pollinators while also validating your credentials for responsible horticultural stewardship; and it's all too rarely encountered in gardens, which confirms your special abilities in seeking out and welcoming to your own garden only the best plants regardless of the herd instincts of the masses.

 

its airy clusters of spidery flowers, arrayed in racemes that have a ziggurat air. Thanks to this seemingly careful array, the racemes are just as interesting in bud as in flower—or even after the flowers themselves have faded, leaving just their green calyces behind. Judging by on-line pictures, the flowers can vary colony to colony, from white to greenish to medium yellow. Those of my colony (a clump of three starter plants from the late lamented nursery in Oswego, NY, Seneca Hill Perennials) are all a lovely solid pale yellow with a fringed lower lip of pure white. Perhaps they were propagated vegetatively. Each flower has a pair of projecting stamens, like long arms reaching out for a hug. If the flowers are the darker medium yellow, there can be substantial raspberry-colored flares on the upper petal; one or both of the stamens can be raspberry, too. (The stamens of my colony are the same pale yellow as the petals.) To me, the flowers are too small for this multicolored scheme to do anything but mute the overall brightness of the clump; the best display from any distance is created by the paler flowers.

 

its large shiny foliage, borne in pairs up square stems. The size of the foliage, number of leaves on each stem, and the density of stems of established clumps, combine to make Collinsonia a good groundcover.

 

its fragrance. The flowers and the leaves both have a citronella-like fragrance. The flowers exude this all by themselves, whereas the leaves need to be crushed to release it.

Flowering season

Summer: July and August.

Color combinations

The pale yellow and white of my flowers would go with everything, as does the dark green foliage. If the flowers of your clumps are of the darker yellow-and-raspberry kind, then you may want to associate Collinsonia with plants that are also celebrating yellow, while avoiding blue, orange, or pink.

Plant partner

As pleasing as they are, the flowers are secondary to the large, shiny, tooth-edged foliage when considering companion plants. If possible, avoid other plants with similarly-shaped leaves of similar size; the Latin for the leaf shape of Collinsonia is ovate. As fantastic as Calycanthus and Leucosceptrum also are in part-shade, their ovate foliage would usually rule them out. Instead, choose shade-tolerant partners with foliage of contrasting shape, texture, and color. In addition to hostas, ferns, and shade-tolerant conifers (mainly Taxus, Cephalotaxus, and Tsuga), any ornamental grass will be foolproof: If similar in scale to Collinsonia, choose among the many forms of Carex and Hakonechloa.

 

Collinsonia would also function as foreground or even groundcover to larger grasses and clumping bamboos, which would themselves provide the dappled shade this species enjoys: Choose amoung the dozens of forms of Miscanthus, Molinia, and Panicum. If you choose bamboo, remember that the only clumper hardy below Zone 7 is Fargesia. (Unless ruthlessly contained, running bamboos quickly obliterate their neighbors.) Fargesia's delicate narrow foliage would be an excellent contrast.

 

Shrubs and small trees with an upright vase shape could be ideal overstory companions. In addition to Acer palmatum, Acer shirasawanum, and Acer japonicum, what about forms of Viburnum without the long oval leaves that are typical of this genus? Leaves of Viburnum x pragense, opulus, sargentii, and trilobum, are all not ovate—as are the multi-lobed leaves of V. acerifolium, whose species name, "acerifolium," means maple-leaved.

 

Similarly, Collinsonia would be a strong player in the shade cast by Buddleja alternifolia and Physocarpus, as well as Ginkgo and Salix in any of their medium-to-large forms. And if you are blessed with large specimens of any Buxus, or Ilex crenata, consider Collinsonia for these dense, small-leaved shrubs' east or north sides.

Where to use it in your garden

Collinsonia is as effective as a specimen clump as it is as a mass-planted groundcover, so it can function as a workhorse foreground planting in a part-shade site, or a choice ornament abutting partners whose foliage is either much larger ('Sum & Substance' hosta, say) or smaller (ferns), or of a clearly different texture (conifers or broadleafs). See 'Plant partners,' above, for more suggestions.

Culture

Part sun and rich moisture-retentive soil. That said, my clump receives no supplemental care, and the foliage stays in good shape the entire season. I'm not aware of reports of leaf scorch when plants receive too much sun or too little water, but that's probably because of this species' rarity in gardens. If you site Collinsonia in full sun, try to provide extra-deep soil and be prepared to water during dry spells. That said, the species is also noted for a surprising tolerance of both heavy soil and, given the large foliage, occasional drought.

How to handle it: The Basics

Collinsonia canadensis can be planted at almost any time; if the clump is in leaf, ensure sufficient water so that the foliage stays hydrated while the plant establishes. In any soil of average moisture retentiveness, and in climates where rainfall is not too fickle, clumps planted when dormant need very little supplemental watering.

 

This species is self-reliant during the growing season, too, and normally doesn't need pinching, staking, thinning, or dead-heading. If you get around to it in the Fall, remove the dead stems; if not, pull them away in the Spring.

 

In my experience, self-seeding isn't a problem, and routine division to maintain vigor isn't necessary.

How to handle it: Another option—or two!

None

Quirks and special cases

The common name of stoneroot is apt: The roots and base of the clump are strikingly woody and difficult to sever during digging or dividing, or to grind when transforming Collinsonia into an herbal preparation. As another of the common names, heal-all, would suggest, Collinsonia has been broadly used as a folk-medicine remedy. Its effectiveness has not been confirmed scientifically.

Downsides

None.

Variants

Despite what seems to be a nice variation in flower color, I'm not aware of any named forms. This elegant perennial would surely be even more so if available in variety. 

Availability

On-line sources sell the seeds, the roots, and entire plants. Sometimes available at native-plant nurseries.

Propagation

By seed and by division. Because the roots are unusually woody and dense, don't be surprised if you need to use your sharpest shovel to dig up a clump. An old pair of loppers or a soil knife could come in handy in separating the base of the clump into sections. Divide in Spring or Fall.  

Native habitat

Despite its name, Collinsonia canadensis is not native to Canada alone. It can be found from Quebec to Florida and as far west as Missouri. It was brought to the attention of European-centric botany and horticulture by Peter Collinson, a British botanist active in North America in the early 18th Century; the species was already known to native herbalists.

 
 
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