Louis Raymond experiments in his own gardens like

a mad scientist, searching out plants that most people have

never seen before & figuring out how to make them perform.- The Boston Globe

…Louis Raymond ensures that trees can grow in Brooklyn…

or just about any other place where concrete consumes

the dirt and skyscrapers shield the sunshine.- USA Today

 
 

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.

 
 
 
 

Plant Profiles

Yellow Root

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As graceful and as bullet-proof as a groundcover can be, yellow root belongs in every garden that has some shade.  Its pale-green leaves seem to be channeling those of celery, and are in lively contrast to the many dark-leaved evergreens that share yellow root's ease in shade.  I grow mine beneath my holly-leaved osmanthus.

 

The deep-burgundy flowers are perfect for any garden with a Morticia Addams theme—as well as for bouquet filler.

 

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Too small to be appreciated from an upright position, they reward kneeling, so you can see the pendulous sprays of blossom in detail.

 

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Each tiny flower has five pointed petals; there's a nicely contrasting chartreuse center.

 

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Xanthorhiza is native to the entire eastern third of the United States, so the flowers are very likely to receive visits from the pollinators they seek.  Nonetheless, in my experience, self-seeding seems modest.

 

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Given the flower's tiny size, and their position mostly beneath the foliage, it's probably not bees that are being courted.  Gnats and flies maybe?  If so, Morticia will be especially pleased.

 

 

Here's how to grow this easy and essential groundcover:


Latin Name

Xanthorhiza simplicissima

Common Name

Yellow Root

Family

Ranunculaceae, the buttercup family.

What kind of plant is it?

Deciduous subshrub.

Hardiness

Zones 4 - 9.

Habit

Stoloniferous and wide-spreading, the roots send up stems readily, resulting in large sweeps of growth.  Unsupported stems achieve a fairly uniform height, for a notably flat-topped look; stems that grow up through larger plants can grow almost twice as high.

Rate of Growth

Medium to fast.

Size in ten years

A colony two to three feet tall where stems don't encounter taller shrubs whose growth is open enough to provide congenial dappled-sun exposure; to four or even five feet tall where they do.  Lateral spread is indefinite.

Texture

Lively, thanks to the foliage, which is, overall, dense enough to work as groundcover even though the leaflets of individual leaves are widely spaced on their petioles.

Grown for

its foliage:  Three or five toothy and light-green leaflets at the end of long petioles that are, themselves, at the tips of the slender branches.  There's a strong resemblance to celery, Apium graveolens, to which the shrub is otherwise unrelated. 

 

its flowers: Interesting even though minute, they're held just below the foliage.  Five-petaled and burgundy, they are in pendulous sprays whose sophistication is your reward for having noticed them in the first place.  I keep forgetting to do this, but they would make great "What is it?" filler in bouquets.

 

its colorful roots: They are chrome-yellow through and through.

 

its tolerance of exposures:  Xanthorhiza is intrepid when growing outward from the part-shade habitat that is its favorite, venturing into fuller sun as well as deeper shade.

 

its groundcovering habit: Xanthorhiza roots spread widely, and produce above-ground growth that is dense enough to function as groundcover.  Although the species is deciduous—and, by the way, provides a colorful show of Fall foliage—the bare vertical stems are modestly appealing during the Winter.  This is more than you can say for the off-season look of other deciduous shade-tolerant groundcovers, such as hostas or hardy geraniums.  Alas, the bark of the stems never got the message from the chrome-yellow of the roots; it's medium tan.  If the stems were chrome-yellow, too, Xanthorhiza would be far more widely planted.  

 

its latin name:  Along with Xanthocerus sorbifolium, a showy Spring-flowering tree native to northern China, Xanthorhiza is the only other hardy plant you're likely to encounter whose name begins with "X."  Xanthosoma is a genus of elephant ear, so is subtropical at the hardiest.  Xylopia aethiopica is an evergreen tree native to Africa, so ditto.  An "X" Garden would have few but strikingly diverse members.

Flowering season

Spring, after the leaves are well emerged.

Color combinations

The light green foliage of Xanthorhiza goes with anything, as do its burgundy flowers.

Partner plants


The flowers of Xanthorhiza are so tiny that it would be difficult to partner on their basis alone, unless you were expecting to appreciate the combinations when kneeling.  If so, go ahead and plant black mondo grass, Ophiopogon planiscapus 'Nigrescens' to the sunny and front side of your Xanthorhiza colony—and be careful to keep the Xanthorhiza from overwhelming it. 

 

There are many more options when it comes to pairing Xanthorhiza on the basis of its habit and foliage.  The leaves' light color and celery-like detailing are in stylish contrast to the foliage of plants with any combination of these attributes:  Darker, lighter, variegated, smaller, larger, rounded, long-and-narrow.  And whose habits can contrast along any of these criteria: Taller and sparingly-stemmed, tight and clumping, densely-foliaged and columnar.  There can be quite a variety in height for partner plants, as well. 

 

Some will be roughly the same scale as Xanthorhiza, and will, therefore, need to share its fondness for shade.  They will also need the most looking after, lest Xanthorhiza infiltrate them.  "At risk" neighbors are worth it as long as they're used sparingly.  Choose contrasting species and cultivars among these genera: Asarum, Carex, Hakonechloa, Hosta, Liriope (and Ophiopogon), Luzula, and Rodgersia—plus all the other large-leaved woodlanders, such as Astilboides, Darmera, Diphylleia, Deinanthe, and Glaucidium.  

 

Partners that are tall enough that their canopies will remain largely above the "waterline" of Xanthorhiza growth are much easier, and should predominate.  The tallest forms of solomon seal are tall enough—but just barely.  Unless you're gardening in the Deep South, where the elephant ears are nearly evergreen and as big as refrigerators, woody partners will be the majority of the neighbors of Xanthorhiza, and will often provide the shade it welcomes.


I've planted my yellow root around an upright broadleaved evergreen, Osmanthus heterophyllus 'Fastigiata', whose dark and small leaves are a strong contrast.  Yellow root makes a particularly fine and fluffy skirt around vertical evergreens, whose look tends to be stiff and whose foliage tends to be dark and small.  (Not that there's a darn thing wrong with stiff, dark, or small.  If nothing else, they are marvelous contrasting qualities to light-green, casually-explorative, and celery-like.)  Other such vertical and evergreen candidates include Taxus baccata 'Flushing', Cephalotaxus harringtonia 'Fastigiata', Cephalotaxus sinensis, Buxus sempervirens 'Graham Blandy', Ilex crenata 'Sky Pencil', and, for those gardening in Zone 7 and warmer, Camellia 'Survivor'

 

Such narrow partners won't, in themselves, provide much of the shade that Xanthorhiza appreciates, but are comfortable with the light shade cast more widely by the more tree-like partners that do.  In addition to full-sized shade trees, smaller "shaders" that are naturals for underplanting with yellow root include the upright forms of Viburnum and Acer palmatum, as well as "tree" clethra, Clethra barbinervis

Where to use it in your garden

Yellow root is almost all too easy as a groundcover and filler among large shrubs and trees, especially where it can ramble at will.  It's especially appealing when the desired colony size is automatically controlled by nearby walls or paving.  In addition to stopping the colony's further expansion, paving also makes it possible for the front edge of the colony to spill out onto the paving with peerless grace.  Be sure that the pavement is partly shaded, too, not just the yellow root it restrains.  Otherwise, the heat from the pavement is likely to scorch the yellow roots's foliage. 

 

Yellow root takes maintenance to incorporate into mixed plantings, especially where nearby neighbors are small enough to be overwhelmed.  But the visuals are so appealing that, occasionally, the effort is worth it.  See both "How to handle it" sections, below, for guidance.

Culture

Part sun to fairly full shade, in any decent to rich soil that doesn't become too dry in hot weather.  Although not a bog plant, Xanthorhiza is very tolerant of dampness and shade.   

How to handle it: The Basics

Plant in Spring or Fall, watering enough to ensure establishment.  Unless the weather is unusually dry in a given season, Xanthorhiza is self-reliant when established.   

 

Xanthorhiza is usually planted as a groundcover, but for a plant that spreads so quickly, and is so hardy and accommodating, it's unaccountably expensive.  You might not, therefore, want to invest in the quantity of plants needed for planting every foot, which provides good coverage in one season.  Maximize the speed of coverage as well as the enthusiasm of the colony long-term by planting in as good soil as you can, mixing in plenty of organic matter as well as creating a loose and easily-colonized structure:  Before planting, dig up the entire area well, and dig in lots of compost while you're at it.  With yellow root as with any groundcover, the results that come from planting in a bed are superior to those from planting in individual holes poked into otherwise unprepared ground.

 

Unless you've sited your colony in a wilder part of your garden, where its ever-outreaching roots aren't a concern, you'll need to control lateral spread three or four years after establishment.  The bright-yellow roots are shallow, strong, and easy to see.  Stand outside the desired perimeter of the colony—right in and even on the growth you're going to remove—and edge around the colony deeply, with a flat-bottomed digging shovel.  The flat-edged shovel will cut through the roots more authoritatively than a spade, which, strictly speaking, will have a pointed bottom.  Flat-bottomed shovels that would normally be used to move gravel or snow aren't sturdy or sharp-edged enough; it's worth it to own a flat-bottom designed specifically for digging. 

 

Then, starting just outside that perimeter cut, pull up the extra growth by hand.  Reach into the shovel's "incision" to locate some of the roots, or expose hunks of them by driving a pitch fork into the ground directly outside the incision and pulling down on it.  Plenty of stringy yellow roots will come into view them.  Grab a few and, following their outward path, yank away. 

 

If you can do this in cooler weather, when the colony is leafless, you can replant the "pullings" to quickly establish other colonies.  (In truth, as long as you water well, and aren't trying to establish a colony where it would get unrelenting sun, you can usually re-establish bare-root stems even if they're in full leaf.)  Or pot them up to donate to plant sales.  It's a rare garden that wouldn't benefit from some yellow root. 

How to handle it: Another option—or two?

Xanthorhiza becomes particularly dense, uniform, and low when the entire colony is cut to the ground every few years.  Do this in early Spring to minimize the length of time you'd be looking at stubble; new growth will emerge in only a few weeks.  Regardless of appearance, it may be more convenient to do this earlier: in Fall or, depending on your climate, anytime in the Winter.  I, myself, will do just about anything possible in Fall in hopes of lessening the work come Spring, and therefore my perennial Spring behind-schedule-ness.  Cut in either—or indeed any—season, the colony of Xanthorhiza will resprout just as well.

Quirks or special cases

None.

Downsides

None.

Variants

Although the outward-bound enthusiasm of the straight species of yellow root makes it an easy large-scale groundcover, it also makes the plant a challenge to use in less expansive and more diverse circumstances:  It will find its way into all the neighboring plants, and will overwhelm those that aren't taller.  The foliage and overall look of Xanthorhiza is so attractive that it would be great to have the option of a cultivar that is clumping instead of running.  And it would be truly swell to have a dwarf cultivar, whether or not it clumped or ran. 

 

Alas, I'm not aware of any forms of Xanthorhiza other than the straight species.  But I live in hope.   

Availability

On-line and at retailers.

Propagation

By division.  The plant self-seeds, too, but not alarmingly.  Given the ease of propagation by division, and the species' apparent inability to produce interesting new forms by seeding, why fuss with seeds?

Native habitat

Xanthorhiza simplicissima is  native to eastern North America, from Maine to northern Florida, and as far west as from Ohio to Texas.

 
 
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