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Design

Great Euphorbias

These cool-looking, critter-proof perennials are easy to love, but where you live affects which ones you should grow

Fine Gardening – Issue 191
Cushion spurge forms an eye-catching mound. Photo: John Glover/gapphotos.com

I’ll never forget my first visit to England thirty years ago. It was April, and the first garden I set foot in was the Royal Botanical Gardens at Kew. The large shrubby euphorbias every where were a sight to behold, since I was coming from the cold winter climate of the U.S. Mid-Atlantic region. I was sold that moment on these seemingly exotic plants. Since then, I’ve grown a fair share of hardy and tender plants from the genus Euphorbia, but truth be told, I’ve only scratched the surface. Comprising one of the largest plant families in the plant kingdom, Euphorbiaceae, commonly referred to as the spurge family, contains approximately 300 genera and about 7,500 species. It would take several lifetimes in many climatic zones to truly explore their full breadth. But throughout the United States and Canada there are spurges that will grow in your garden, either as hardy perennials or as potted plants summered outdoors and brought in for the cold months.

One thing all spurges have in common is their milky sap, which is very evident upon breaking or cutting a stem. This liquid latex, a lifeblood of Euphorbia, is a deterrent for animals, which would otherwise find these plants tasty. It also is a known skin irritant to some people, and therefore caution should be taken when working with these plants. But I would say that’s the only caveat of this useful genus. The best part of spurges is their infinite variety in plant form and function. Some are hardy workhorse perennials with more traditional forms, while others look more like Dr. Seuss plants. With a genus so diverse, there are species that will do well in nearly any part of North America.

Top picks for cooler climates

The first spurge I ever encountered, and one that I eventually grew in my first garden as a child, was cushion spurge (E. epithymoides, Zones 4–8). Its eye-catching chartreuse flowers held on a low 12- to 18-inch mound of foliage are a beacon in the awakening spring garden. It is one of the first herbaceous perennials of the spring season, its bracts positively glow, and it can be a companion to spring-flowering bulbs such as grape hyacinth and late-season tulips.

Robb’s spurge
Robb’s spurge is a great ground cover for dry shade. Photo: Jonathan Buckley/gapphotos.com

A real workhorse in the right situation is Robb’s spurge (E. robbiae, Zones 6–9). Because of its running tendencies, it is best used as a ground cover. It can take dry shade once established. Deep green leaves that form colonies sprout from lime green flowering stalks in midspring. In my experience, Robb’s spurge can be slow to establish; once settled, however, it can be pervasive, so keep it on its own or with other strong-willed perennials. Also, try to site it away from strong winter sun and desiccating winter winds in colder climates, which can burn the evergreen foliage and lead ultimately to losing a spring season of flowering.

Marsh spurge
Marsh spurge is the perfect choice for wet spots. Photo: Nancy J. Ondra

The next three euphorbias have a similar form: their stems reach upward, then exponentially branch outward, forming an expanding mound 3 feet high and nearly as wide. Two are perennials, and the third is an annual that will reliably self-sow. Marsh spurge (E. palustris, Zones 5–10) is a large-scale perennial that is happiest when grown in moist or marshy ground, although it is not limited to such soils. An outlier in a genus that is known for being more suited to Mediterranean or desert climates, marsh spurge blooms in late spring with large heads of bright, acid yellow bracts. It is well suited for mingling with other moisture-loving plants, such as Siberian or Japanese iris (Iris spp. and cvs., Zones 4–9), and looks wonderful with late-blooming, large-headed flowering alliums (Allium spp. and cvs., Zones 3–9).

Flowering spurge
Flowering spurge is a tall, strong-stemmed native. Photo: Bill Johnson

An underused U.S. native, flowering spurge (E. corollata, Zones 4–7) is only now getting some of its due, thanks to being featured in many Midwest prairie-inspired gardens, such as the Lurie Garden in Chicago, where Piet Oudolf has masterfully threaded it through the peak summer season’s riot of pinks, purples, and yellows. Flowering spurge emerges later than many perennials. Its stems with greenish-gray leaves grow straight upward, then diverge into a cloud-like effect of small white bracts. Think of it as a very tough baby’s breath (Gypsophila paniculata, Zones 3–9) that does not require staking! Now that it is becoming more widely known, nurseries are offering it for purchase. Young plants are slow to get established, but your patience will be rewarded.

Snow-on-the-Mountain
Snow-on-the-mountain is a self-sowing North American native. Photo: Steve Aitken

Snow-on-the-mountain (E. marginata, annual) is an annual species that is native to the United States and Canada. It is very showy, with multitudinous stark white bracts that give it its frost-inspired common name. The seeds are hardy from Zone 5 southward, so you can expect this beauty to be reliably self-sowing. In fact, self-sown plants give the best results, as this annual resents transplanting. Scatter seeds where you want new plants to establish, and always allow some plants to go to seed each year to ensure a recurring show. Snow-on-the-mountain requires full sun and does well in average to lean soil.

‘Cherokee’ Martin’s spurge
‘Cherokee’ Martin’s spurge sports striking foliage and a compact habit. Photo: courtesy of Plant Delights Nursery

‘Cherokee’ Martin’s spurge (E. × martinii ‘Cherokee’, Zones 6–8) is a cross between two different species, E. characias and E. amygdaloides. It has hybrid vigor and striking purple-red foliage. In spring, silvery-purple bracts cover the flowering stems. At less than 18 inches tall and wide, its size is compact, making it the perfect fit for the front of the garden. Perhaps best of all, it can take dry conditions once established.

flower structure of spurge
Illustration: Conor Kovatch

The unique flower structure of spurge

What most people think of as Euphorbia flowers are in reality the showy bracts, which are often brightly colored. The actual flowering parts are much smaller and are held inside or framed by the showy bracts. This is most easily seen in the ubiquitous poinsettia (E. pulcherrima, Zones 10–11) holiday plant. The red, pink, white, or variegated bracts are what people purchase the plant for, but the true flowers are the much smaller, yellow, knoblike tufts in the center.

 

Best bets for warmer locales

It was twenty years after my first visit to England that I started experimenting with this second set of Euphorbia, which come from warmer regions of the world and, as such, are not as hardy as those in the first group. Their success in the garden relies on the top growth not getting zapped by intense winter cold. These are great plants for those living in warmer regions and even for those who live in cooler spots but like pushing the zonal limits or growing in containers.

‘Glacier Blue’ Mediterranean spurge
‘Glacier Blue’ Mediterranean spurge takes variegation to the next level. Photo: Nancy J. Ondra

‘Glacier Blue’ Mediterranean spurge (E. characias ‘Glacier Blue’, Zones 7–9) has enhanced blue leaves compared to the green-blue of the species. Each leaf is irregularly margined with white, which contrasts brilliantly with the blue. I’ve known this 2-foot-tall-and-wide plant to survive in Boston in protected places. Good drainage in winter, though, is key. Spring brings elongated spikes (12 to 18 inches tall) of variegated bracts that echo the leaves below.

‘Galaxy Glow’ Mediterranean spurge
‘Galaxy Glow’ Mediterranean spurge is all about the flowers. Photo: DoreenWynja.com

‘Galaxy Glow’ Mediterranean spurge (E. characias ‘Galaxy Glow’, Zones 7–9) is a recent selection brought into the gardening world by plantsman Pat McCracken. The bluish leaves are burnished with coppery red tones, which is beautiful all on its own. Greenish bracts appear later in the season and are flushed with rose-bronze especially as they age. This is not a small plant—it can get up to 2 feet tall and spread much wider (nearly 3 feet is common)—so plan accordingly.

‘Tiny Tim’ Martin’s spurge
‘Tiny Tim’ Martin’s spurge has the best shape by far. Photo: Joshua McCullough

Many spurges can form a shrublike plant 3 to 5 feet tall and wide, which is awesome—if you have the space. A more diminutive option can be found in ‘Tiny Tim’ Martin’s spurge (E. × martinii ‘Tiny Tim’, Zones 7–9). It forms a compact shrublike ball only a foot high and wide and blooms not only in spring but also throughout the growing season. Each bract has a red “eye” in its center, which draws lots of attention for such dainty blooms.

Caribbean Copper plant
Caribbean copper plant is a tropical worth overwintering. Photo: Michelle Gervais

Caribbean copper plant (E. cotinifolia, Zones 9–10) has deep, wine-colored rounded leaves and forms a 6- to 8-foot-tall-and-wide shrub or small tree over time. The foliage is reminiscent of a smoke bush (Cotinus spp. and cvs., Zones 4–9), and just like the colored-leaved forms of smoke bush, this woody spurge can be used to break up monotonous green foliage schemes or used as a dark foil for any number of flowering plants. It can also be planted in the garden in colder climates and overwintered in a frost-free room (expect it to get just 4 to 6 feet tall in this case). Plants can be left to go dormant and will resprout the following summer once the heat arrives.

‘Ascot Rainbow’ Martin’s spurge
‘Ascot Rainbow’ Martin’s spurge is a technicolor wonder. Photo: DoreenWynja.com

‘Ascot Rainbow’ Martin’s spurge (E. × martinii ‘Ascot Rainbow’, Zones 7–9) has risen to prominence in the past decade, and for good reason. Its green leaves are irregularly variegated with yellow, augmented with highlights of bronze-red in cooler weather. The 12- to 18-inch-tall flower spikes also contain variegated bracts. I find in the Mid-Atlantic region that its stems are often winter-killed and that it is not as hardy as the similar-looking E. characias and its cultivars. It is great to use as an annual in a container, where it will continue to produce new flowering stems all season and look handsome well into autumn. In containers, store it in an unheated garage, and then put it out in early spring after the frost-free date.

Silver spurge
Silver spurge cascades with sparkling elegance. Photo: Joshua McCullough

Most of the spurges mentioned so far are upright, but silver spurge (E. rigida, Zones 7–10) is a sprawling, 2-foot-tall-and-wide, stiff-stemmed plant with blue stems and equally blue sharply pointed leaves. It blooms with acid yellow bracts in early spring on stems produced the season before. It thrives in hot, baking places that do not get much water, making it a perfect xeriscaping candidate. Silver spurge even thrives in the rocky home landscapes of places such as California’s Coachella Valley.

Sticks-on-fire
Sticks-on-fire is the most unique variety—hands down. Photo: DoreenWynja.com

Some spurges are only hardy in a relatively small part of the country yet are becoming more popular in other regions as container plants for the summer season. There are hundreds of species of succulent spurge, all of which have adapted to extremely arid climates, their stems being a form of water storage. Sticks-on-fire (E. tirucallii ‘Rosea’, Zones 9–10) is a true eye-catching succulent that doesn’t fit the norms of what people in temperate climates think plants should look like. Basically, sticks-on-fire is a leafless shrub reaching up to 4 to 6 feet tall and wide in a pot, or up to 25 feet tall if planted in the ground in warm climates, with stems of yellow-green highlighted with pink and orange tones depending on the temperature. The growth rises upward and outward, bifurcating as it grows taller. Think of it as a living coral for your dryland garden. Sticks-on-fire mixes well with other succulent plants from arid regions and does very well in dry containers. It can be used as a houseplant in the winter months in a bright and sunny window. Just remember to acclimatize it to the outdoor sun upon moving it outside for the season.


Gary Keim is a horticulturist and designer based in Landsdowne, Pennsylvania.

 

This article first appeared in issue #191 of Fine Gardening under the title “Spurge: Great Plant, Bad Name.”

 

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