A Gardening Journal

Must Have: Caribbean Copper Bush

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I don't think I could ever grow enough plants with colorful foliage. While there are many whose leaves are gold or purple or blue or white, red isn't nearly as common. The red leaves of this tropical shrub are as eyecatching as can be. As if the bright leaves and even brighter veins aren't showy enough, the small heads of green and white flowers perched at the tips of new stems add a contrast that is at once restrained and exuberant. Caribbean copper plant is near the top of this year's Must Have list.

 

The tiny flowers can mature to lime-green three-lobed fruits, which add some comic clumsiness to the flowers' tiny tight compactness.

 

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Even if it never flowered, Euphorbia cotinifolia 'Atropurpurea' is essential: The young leaves are unusually translucent, transmitting available light while turning it garnet red. This is a plant to grow with all possible young foliage; see the second "How to handle it" box, below.  It's also the plant to site to the west of where you sit, so the afternoon sun can set the plant aglow hour after hour. 

  

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The foliage of Caribbean copper plant is about as "copper" as that of "copper" beeches. Clearly, it's really a rich burgundy, especially in the strong sun and high heat this Mexican native prefers. The plant is self-branching enough that the natural habit is spreading and multi-trunked. In the tropics, Euphorbia cotinifolia has a similar habit and size to upright purple-leaved Japanese maples that grace gardens farther north. 

 

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Here's how to grow this dramatic, versatile succulent:

 

Latin Name

Euphorbia cotinifolia; also Euphorbia cotinifolia 'Atropurpurea'

Common Name

Caribbean copper bush, tropical smoke bush

Family

Euphorbiaceae, the Euphorbia family.

What kind of plant is it?

Shrub or small tree, capable of growing as a broadleaved evergreen, or becoming deciduous and dormant in cool but frost-free conditions. Fast-growing enough to succeed as a cutting-grown annual. 

Hardiness

Zones 10 - 11.

Habit

Young plants are open and gawky but, because the upright stems produce side branches spontaneously, growth usually becomes dense. When plants receive enough water, the foliage provides full screening. Multi-stemmed unless trained to a single trunk. Responds readily to pruning and training, making specimens of topiary-like density and smooth-surfaced tightness possible. Stunning as a standard.

Rate of Growth

Fast when the plant receives its preferred conditions of full sun, heat, moderate water, and excellent drainage.

Size in ten years

Where growing in-ground in the tropics, usually ten to fifteen feet tall and wide, although if you keep limbing it up higher and higher it can become a tree to thirty feet tall. Smaller in containers. Even when used as a cutting-grown annual, can still achieve three to five feet by frost.

Texture

Dense but, thanks to the difference in color of emerging versus mature foliage—blood red when young, aging to burgundy with overlays of dusty blue—never dull. Further, happy specimens produce small white and green clusters of tiny bracts and even tinier flowers at the stem tips, which shimmer pointillistically just above the perfect backing of the darker foliage.

Grown for

its new growth: Although the translucent foliage appears to be delicate, the leaves are actually quite durable; I don't ever recall seeing ones that had become torn or kinked. They are smooth-edged and rounded, and usually borne in threes, each spaced equally around the stem, with plenty of separation between the trios above and below. When the plant is in its season of bloom, the last leaves formed before flowering tend to be in pairs, with the pedicel that bears the flower cluster emerging next. Foliage emerges a deep red with red-pink veins; thanks to its prowess at transmitting light, the appearance of new foliage is so lively it could be described as a pulsating bloody red. It matures to a muted burgundy that is softened by a bluish bloom, but the startling and intense color of the juvenile coloring can be retained in the veins and the petioles. The slender and flexible young stems are also red. All of these colors contrast well with the pale gray bark of older stems.

 

The foliage is a dead ringer in coloring, size, shape, and translucency with that of the hardy smokebush hybrid Cotinus x 'Grace'. It is a hybrid of the America smokebush species, Cotinus obovatus, and the European one, Cotinus coggygria, and its mature foliage also has a bluish cast. The mature foliage of smokebush cutivars derived solely of Cotinus coggygria, such as 'Velvet Cloak', is distinctly darker.

 

Although the combination of red, slate-blue, burgundy, and gray is thrilling in itself, the show can be improved still more by the addition of lime green, cream, or white. This can be achieved naturally, by allowing the plant to flower, as well as by skillful combinations with other plants. If you like to live dangerously, you could try adding red, but the match with the young foliage of the Euphorbia needs to be exact. See, below, "How to handle it: Another option—or two!" as well as "Plant partners."

 

In less-than-full sun, older leaves become a less interesting greenish burgundy. See "How to handle it: Another option—or two!" for tactics to maximize foliage color.

 

its flowers: The greenish "petals" with white fringe are actually bracts; the true flowers are minute but (with a magnifying glass) a delightful assemblage of burgundy-tipped stamens surrounding a single projecting pistil. If the flowers are pollinated successfully, the pistil matures to a fingernail-sized green fruit that is a satisfying show in itself. The show is enhanced immensely by the backdrop of the dark foliage. (Euphorbia flowers may be small, but they are surprisingly complex: See the discussion of Cyathia here.)

 

its love of heat: Unlike some popular hardy plants with purple foliage—beeches and Japanese maples at the top of the list—the vibrant coloring of the foliage of Euphorbia cotinifolia doesn't fade when the weather is sweltering. Even better, new foliage, whose saturated red coloring is particularly intense, continues to emerge all season long.

 

its speed of growth: As long as the weather is hot, the sun is strong, and the plant receives enough water (but not so much that there's a risk of root rot), Euphorbia cotinifolia grows quickly. If the shrub is sited where it doesn't have room for free-range growth, you'll need to cut it back several times a season. A rooted cutting that is a foot or so high at the time of planting-out in late May will usually be several times that height by September.

 

its tolerance of pruning: Euphorbia cotinifolia drops its lower leaves as the plant grows, especially when planted in containers, where the roots can quickly fill the available volume of soil. While you may want your plant to adopt a more tree-like shape by developing a trunk that's free of foliage, you might not want to have to keep shifting the plant to larger and larger pots just to prevent undue loss of lower foliage. Happily, you can keep a steady-state balance between root room and the amount of foliage those roots can support by controlling the size of the plant's canopy of branches: Euphorbia cotinifolia tolerates pruning beautifully. See the second "How to handle it" box for pruning strategies that also enhance the plant's performance and style.

 

its unpalatability: As is typical for Euphorbia, the sap is both unpleasantly viscous as well as outright poisonous. Euphorbia foliage is normally free from even browsers' test nibbles, let alone their full-on foraging.

Flowering season

When growing year-round in the sunny, warm, frost-free conditions it enjoys best, Euphorbia cotinifolia flowers in the Spring. When growing in slightly cooler (but still frost-free) conditions, flowering can be delayed to early Summer. When used as a cutting-grown annual, flowering might occur at almost any time in the season—or not at all.  

Color combinations

The palette of Euphorbia cotinifolia is sophisticated as well as nuanced: blood red of new leaves, bluish burgundy of mature ones, greenish burgundy of leaves that don't receive full sun, and the lime green and white of the flower clusters and, if you're lucky, the fruit that follows. So there's no need for still other colors, which will only distract from a show that is, already, substantial as well as sustained. Resist the temptation, either to add "hots" like orange or deep yellow (even though, in simpler circumstances, they would go well with both the red and the burgundy) as well as blue or pink (even if they would call out to the muted coloring of the mature leaves, they would probably clash with the strong red of juvenile growth).

 

Instead, increase the presence of one of the colors already in play. Because blue-burgundy is this plant's predominant color, at least in sheer surface area of foliage, there's no need for more of it: Choose among the accent colors of lime green, white, and blood red. See "Plant partners," below.

Plant Partners

Combine Euphorbia cotinifolia first on the basis of coloring and only secondarily on the basis of texture. The shrub's coloring is so specific and quirky that if the neighboring plants aren't clearly producing some sleek and inspired jazz solely on the basis of hue, the results will be out of tune no matter how clever the improvisations involving texture, scale, or flowers.

 

Handily, the leaves of many plants with foliage that is striped in green and white are also grassy or sword-like, guaranteeing a color harmony that is as strong as the textural contrast. It might make sense to set a containered specimen of Euphorbia cotinifolia near a clump of white-striped miscanthus. Or yucca or agave or furcraea or beschorneria or dianella

 

Or you could call attention to the blue of the mature foliage of this Euphorbia by cultivating a nearby specimen of Opuntia violaceae, whose pads are distinctly blue. Just don't look in Spring, when the cactus's bright-yellow flowers are out.

 

Some flowering plants are available with blooms the exact shade of red as the young leaves of this Euphorbia. Although a number of cannas have red flowers, if they are borne by plants that also have purple foliage, it would be an overload. (Avoid, as well, the multi-color forms with flowers in red and yellow.) Instead, choose a red-flowered cultivar such as 'Ace of Spades' or 'Black Magic', with dark red flowers and foliage that is mostly green or, at best, edged with purple. Dahlias with what suppliers love to call "black red" flowers are likely to match well, too: Consider 'Kaisha Lee', 'Lights Out', 'Night Out', and 'Voodoo'; as always with dahlias, each Spring brings still more cultivars to the market. 

 

Like dahlias, new forms of coleus are available each Spring. Look at forms that tolerate sun and that have leaves that are lime-green or palest yellow. 

Where to use it in your garden

Where hardy, Euphorbia cotinifolia can function as a clipped foundation shrub or a colorful accent shrub with the impact and size of a purple-leaved smokebush. Or, if you've made the commitment to limbing-up, as a tree with the foliage coloring, habit, and overall size of a purple-leaved Japanese maple.

 

As a container subject that is carried year to year, this cultivar is most easily handled by training it as a standard. Happily, standarizing also ensures that the shrub assumes—and retains—a striking shape as well as a relatively constant (and compact) overall size. Portable as well as focal, the standard is a natural star of any warm and full-sun location, especially when partnered with other container specimens whose coloring of foliage and flowers meshes exactly with that of the Euphorbia.

 

Euphorbia cotinifolia also stars when young plants are used as annuals, as one of the cast of diverse annuals in a large container. The same openness and gawkyness that makes a youngster unsuccessful as a specimen makes it all the easier to plant directly amid other hot-weather lovers that are either denser and shorter, or even taller and wispier.

 

See "Plant partners," above.

Culture

Full sun with good drainage. When used as one of a group of annuals in a container where the weather can be counted on to be reliably hot, rich topsoil with regular watering yields the fastest and fullest growth. In such circumstances, young plants will grow so fast that their roots will usually colonize the available volume of soil fully and quickly. The challenge will be providing enough moisture, not avoiding an excess. When growing in-ground—whether as an annual or as a shrub or tree—well-draining soil is essential, even at the expense of fertility, so that any possibility of root rot is avoided.

 

Although the succulent young stems ensure drought tolerance, the large quantity of foliage that an established plant displays can't be maintained during challenging circumstances. Euphorbia cotinifolia will drop its gorgeous foliage readily if stressed by drought or chill, releafing only when there's enough moisture and heat to sustain leaves that are, for the genus, surprisingly broad, large, thin, and numerous. Although this ability to become deciduous is a sign of distress during the growing season, it's a plus in the off-season: By dropping leaves, the shrub is able to enter a dormancy deep enough to increase its chances of survival. See the second "How to handle it" box, below.

How to handle it: The Basics.

Plant in Spring, after danger of frost is past: Only if it's warm enough to set out tomato plants is it warm enough to set out Euphorbia continifolia. Water only when needed, by touching the soil surface with your finger. Soil that is even moist, let alone wet, feels distinctly cooler than soil that is dry; when damp, particles will adhere to your finger more readily than when dry. Delay watering until the soil an inch below the surface feels dry.

 

Whether used as an annual or being grown-on for years as a specimen-to-be, formative pruning the first year isn't usually needed. Remove lower foliage that is in process of being shed when a containered Euphorbia has become pot-bound.

How to handle: Another option—or two!

When the goal is to keep a Euphorbia cotinifolia thriving year after year, pruning can help control size and reduce the amount of foliage that doesn't receive full sun, while also training the shrub into an overall shape that is effective and, even, exciting.

 

In the dry, hot, frost-free tropical climates it prefers, Euphorbia cotinifolia can be pruned at any time—and will often need it. Elsewhere, prune in Spring. It is probably best to delay until the leaf buds of new growth have become active, rather than pruning in late Winter, when the plant is still dormant. In this regard, handle Euphorbia cotinifolia like you would Buddleja davidii or culinary sage: Plants can be pruned drastically as soon as new growth is apparent, but pruning just a week or two earlier, when the plant is still dormant, can be fatal.

 

Tips of young growth of established shrubs often terminate in a flower cluster, with new stems emerging from side buds below. Thus, Euphorbia cotinifolia is somewhat self-pruning, often forming a wide canopy of branches and foliage on its own. With a natural width in excess of ten feet, pruning to control size is often needed. The result is mounding shrubs of impressive vigor but a cramped gestalt. The easiest solution is to limb-up, exposing the attractive gray bark of mature stems as you allow new top growth to increase freely. In time, that mound of growth wil have transformed into a multi-trunked ornamental tree.

 

Whether the shrub is growing in the ground or in a container, it can have the smallest sustainable footprint as well as the greatest aesthetic impact when trained as a standard. Stake the single stem of a young starter plant so it grows vertically to the intended height. Pinch the tip (but only in mid-Spring unless you're gardening in warm, dry, tropics) to encourage side branches; at the same time, clip away any lower side branches to reveal the developing trunk.

 

If growing Euphorbia cotinifolia north of the tropics, where it will enter an off-season dormancy when brought into shelter, reduce or even cease watering when the shrub begins shedding foliage as the weather cools. Then water sparingly, if at all, during dormancy. Lead from behind all through the Winter, waiting for the plant to indicate that Spring has arrived via swelling of its leaf buds before providing anything other than the minimum amount of water needed to prevent shriveling of the young stems. When new growth is clearly evident, then prune back the branches that form the standard's head. Depending on the size of your standard and its age, this pruning can be superficial or drastic. I'll never forget seeing a group of old potted standards of Euphorbia cotinifolia at Wave Hill; their thick branches were pruned back to stubs in late Spring, awaiting the profuse resprouting that truly warm weather will bring.

 

If creation of a full-headed standard has become too easy, you may want to experiment with creating a standard that also flowers. Euphorbia cotinifolia usually blooms in Spring, at the tips of stems that had emerged the previous Summer and Fall. Pruning back those branches in Spring is likely to reduce or even eliminate flowering. Try delaying your pruning until early or even mid-Summer, after flowering has peaked. New stems should appear quickly in the heat of high Summer, and still have a long enough growing season to mature sufficiently to bloom the following Spring.  

Quirks and special cases

The sticky white sap is so poisonous that it can be added to water to stun fish, causing them to float to the surface and be readily harvestable. It can also be used to tip poison arrows.

Downsides

The sap: It is sticky, poisonous if ingested and, often, irritating when in contact with skin. Wear protective goggles and clothing when working on larger specimens of Euphorbia cotinifolia. In mild climates, they can grow large enough to function as small trees, with branches high enough to be walked under. Sap can drip from the "stump" of even the smallest cut segment, making a mess of a walkway (or the hair of a passerby) below. Any sap that drips into an upturned eye can be reason for a trip to the emergency room. Euphorbia cotinifolia that has become arboreal in habit can be dramatic—but is only practical and pleasant when sited well back in a bed deep enough to keep the plant entirely away from passersby. See above, "How to handle it: Another option—or two!"

 

Regardless of the size of the plant, pruning Euphorbia cotinifolia is still an inherently messy task: The sap oozing from pruned segments will soon gum up the pruners, or irritate unprotected skin, or turn the sleeves and gloves and pants-legs that need to protect skin into sticky messes. Promptly wash tools, gloves, and clothing, let alone any exposed skin, to clean off the sap before it dries.

 

The sensitivity to frost: Euphorbia cotinifolia is completely tropical and, after even a mild freeze, there seems to be little ability to resprout from lower down on the trunk, nor from its base or directly from the roots. If this Euphorbia is frosted, it's usually toast. I write from painful experience, when the greenhouse furnace failed one Winter night.

Variants

I'm not aware of any forms of Euphorbia cotinifolia other than 'Atropurpurea'. No doubt the straight species is seen in Nature, but in commerce I've never seen anything offered other than 'Atropurpurea'. Without its extraordinary coloring, the foliage is merely a pleasant green, and the subtle flowers, lacking their vibrant backing of blood and burgundy, so to speak, lose their appeal. No surprise, then, that the cultivar is what's sold, and that the 'Atropurpurea' name is so often omitted, even by nurseries that are picky about their nomenclature. 

Availability

On-line and, as an annual, at specialty retailers. Where fully hardy, this easy and colorful shrub is probably available even at the big boxes.

Propagation

By cuttings. 

Native habitat

Euphorbia cotinifolia is native to Mexico.

 
 
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