Designing with euphorbias
by CAROL KLEIN
IN THIS SERIES we demonstrate a few effective plant combinations, restricted only by the simple ground rule that the plants put together must enjoy similar conditions and be able to live together peaceably.
Here, the genus Euphorbia is the lead player. It is a big group, with species suitable to the whole gamut of cultural conditions, from sunbaked arid slopes to heavy, marshy clay. Some are evergreen, others deciduous. All are distinguished by large heads of lime-green bracts (now correctly called cyathium leaves) within which the tiny flowers and eventually the spherical seed capsules are held. These heads fast for months. It is this longevity of display, combined with strong structure, that makes the great majority such valuable garden plants.
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(1) Euphorbia palustris; (2) Acarthus mollis ‘Hollard’s Gold’; (3) Aqulcgia ‘Hcnsol Harebell’; (4) Chaerophyllum hirsutum ‘Roseum’; (5) Doronicum x excelsum ‘Harpur Crewe’
This is a robust and invigorating combination. The euphorbia has the strongest form and the most vibrant color within the partnership. Both the chaerophyllum and the aquilegia exaggerate the brilliance of its bright, beaconlike heads with blues and purples from the opposite side of the spectrum. Meanwhile, the simple yellow daisies of the doronicum add a joyous endorsement of spring vigor. This color is echoed in the large, divided leaves of the acanthus, their golden, shiny surface reflecting light upwards.
Euphorbia palustris (USDA Zone 5] is an imposing European spurge that occurs in damp, open ground. In the garden, in moisture-retentive soil, it will reach three feet, and by fall will be just as wide across. It provides a spectacular focus dunng spring, when the closepacked heads gradually loosen up to create ever-larger bouquets of vivid gamboge yellow. Its bronzed, early foliage has a luscious, velvety quality that creates an impression of newness. In fall there is a second performance, when the whole plant is set aflame.
Acanthus mollis ‘Hollard’s Gold’ (Zone 7) has all the virtues and faults of the green-leaved species, with the added pizazz of lime-yellow leaves. If you want it in specific places (or live north of Zone 7), sink a potted specimen in the soil to curb its wandering inclinations.
One of the most vigorous and long-lived of all columbines. Aquilegia ‘Hensol Harebell’ [Zone 3] has wide, long-spurred, blue-purple flowers that are among the most graceful in the genus. Foiage in spring is lush bright green and appears early. It will succeed in sun or shade but prefers substantial soil.
Chaerophyllum hirsutum ‘Roseum’ [Zone 5] is a big umbeitifer with a dainty presence created by platforms of tiny purple-pink flowers. Its basal foliage is ferny, its branching stems dark crimson. Happy in sun or shade.
Doronicum x excelsum “Harpur Crewe” [Zone 4) could not be more straightforward. Its fat buds appear early in the year among clumps of fresh, heart-shaped leaves. Rower stems shoot up and branch outward, each terminating in a bright yellow daisy. Flowering can last for three months, if spent stems are removed promptly.
(1) Euphorbia x mardinii; (2) Foeniculum vulgare ‘Purpureum’; (3) Milium effusum ‘Aureum’: (4) Polenbilla atrosanguinea; (5) Prirrula Gold-laced Group; (6) Rheum ‘Ace of Hearts’
A close color range from green through yellow to red gives this association an integrated feel. The forms and textures of the plants within it are disparate, creating a visually stimulating picture, while the color harmonies marry one plant to another.
Despite its background position, the euphorbia’s bold structure is the most striking element. This spurge doesn’t know how to play second fiddle. Among its strong red stems, clad in whorls of reddish-green leaves, bronze fennel meanders, its fluffy texture a complete contrast to the spurge’s strong geometry.
The bold leaves of Rheum Ace of Hearts’ make an emphatic statement, particularly when their red reverse is visible. This crimson is picked up by the bunched flowers of the polyanthus. Primula Gold-laced Group usually has a blacker base color, but this rich crimson specimen works here, reiterating the red “eyes” of the spurge. The golden edges and centers of the primula are close in color to the blades of Milium effusum ‘Aureum’, which has started its flush of spring growth.
In the foreground, two clumps of Potentilla atrosanguinea lend a reflective edge to the planting. Later, their silvery foliage will obscure the faded primulas, shading them from the hot summer sun. Its flowers are a deliciously dark velvety red.
Versatile Euphorbia x martinii (Zone 7) is a hybrid between E. characias, a huge evergreen Mediterranean species, and E amygdaloides, the wood spurge. The former needs a hot dry site; the latter grows at the woodland edge or among scrubby undergrowth in hedges and ditches. Euphorbia x martinii can cope with either site, although it flourishes in an open space with good substantial soil. It inherits the general deportment of E characias, although at two feet it is a more useful height. Its striking reddish foliage is the legacy of E amygdaloides.
Most of us are familiar with bronze fennel, Foeniculum vulgare ‘Purpureum’ (Zone 4). Its froth of fuzzy foliage mixes easily with neighboring plants but is inclined to become overbearing on occasions. In flower, it becomes a giant, with six-foot stems supporting large heads of soft yellow flowers. It is tempting to leave the seed heads for their architectural value, but such inaction will result in wall-to-wall fennel.
Bowies’ golden grass, Milium effusum ‘Aureum’ (annual), is one of spring’s most vivacious heralds. Its bright yellow blades rise afresh from winter torpor and in no time at all it is spreading its light far and wide. It seeds prolifically, its progeny adding little pools of brightness in dark places.
Potentilla atrosanguinea (Zone 5] hails from the Himalaya region. In nature its flower color varies from yellow and orange to a deep, dark red, often with dark anthers to boot. Some flowers are almost black. Easy to cultivate, it is a rewarding plant, producing not only exciting ribbed foliage but also endless stems of flowers until frost.
In cultivation for centuries, Primula Gold-laced Group (Zone 4) originated as a florist’s flower, refined and hybridized for exhibition. More to the point, it is a good doer. It seems happy in either sun or shade and in both alkaline and acid soils. Its petals are dark crimson or black and each is rimmed in and centered by bright yellow.
Rheum ‘Ace of Hearts’ (Zone 5) is a scaled-down version of R palmatum ‘Atropurpureum’ that can be accommodated in even a small bed or border. Its bold leaves are bronze on emerging, and their reverse remains red throughout the growing season. Tall heads of reddish fluffy flowers are an added attraction in summer.
(1) Euphorbia ‘Excalibur’; (2) Iris pseudacorus ‘Variegata’ (3) Lysimachia ciliata ‘Firecracker’; (4) Thalictrum flavum ‘Illuminator’; (5) Vcronica gentianoides
Here, a limited color palette combined with a stimulating mixture of form gives this association a subtle but fresh feel. It could only be spring. Bright splashes of creamy yellow foliage and pale blue flowers draw the eye in close to the subtly colored mounds of the euphorbia foliage, while the dark chocolate stems of the loosestrife form a shadowy undercarpet. A nuance of greeny-blue in the spurge’s leaves is picked up in the pale blue spires of the veronica. The glorious “maidenhair” foliage of the thalictrum is at its springtime best, its pale yellow foliage touched with a hint of pink, again echoed in the midribs of the euphorbia leaves.
As the seasons progress, the euphorbia maintains its color, while the lysimachia, a very voluble plant, will dash around thrusting up its stems wherever an opportunity presents itself. There will be starry yellow flowers, and in the fall its foliage will flush gradually to reds and oranges.
Euphorbia ‘Excalibur’ (Zone 5) is an irresistible plant. It appears to be a hybrid between E. sikkimensis and E palustris, with similar color to the first while exhibiting the structure and growth habit of the latter. The coolness and class of its foliage are its raison d’etre. The exquisite color and the disposition of its leaves in a breathtaking symmetry are second to none, it thrives on clay soil and is happy in dappled shade or sun.
Iris pseudacorus ‘Variegata’ (Zone 4) is a colorful version of the yellow flag iris, which frequents watery places all over Europe and is naturalized in North America. Its bold cream-and-green swords pierce the ground in spring, providing a bright vertical accent in early piantings. By late summer it has lost its variegation but is still useful among mounds of herbaceous plants. Any heavy soil suits it—the wetter the better. (Note: I. pseudacorus should not be allowed to self-seed.)
Lysimachia ciliata (Zone 3) is a native North American. Its typically pale “milk chocolate” foliage is exchanged for rich, dark chocolate in the cultivar ‘Firecracker’. It is an inveterate colonizer, but since its roots are superficial, it is easy to keep it under control. It mixes well, linking together diverse individuals.
An easy and beautiful plant, Thalictrum flavum (Zone 4) has long been used in herbaceous plantings. Its fine glaucous foliage is useful on its own account, making wide though well-disciplined mounds with towering stems of fluffy citric yellow flowers. ‘Illuminator’ adds the bonus of lemon leaves tinged with pink. One of the most noticeable of spring’s plants, it is at its best on heavy soil.
Veronica gentianoides [Zone 4] is much underused. Most speedwells prefer a sunny site, but V. gentianoides is happy even in dry shade. On opening, the blue of the flowers mixed with the green of the calyces make the flower spikes appear almost turquoise. Its capacity to cope with shade and to endure harsh winters make it immensely useful.
(1) Euphorbia polychroma; (2) Sambucus nigra ‘Thundercloud’; (3) Tulipa ‘Princses Irene’
Simplicity and blocks of color are the key here. Each element can be appreciated on its own or for the way it contributes to the whole. There are only two permanent players in this combination—the euphorbia and the elder. They make a telling pair, but when they are joined by the orange tulips in terra-cotta pots, the effect is stunning. The canopy of bronze leaves frames the bright lights of the euphorbia, and the bold tulips provide blocks of fiery color. By the time the spent tulips are removed, platforms of pink flowers will have started to adorn the elder’s bronze foliage, and the euphorbia will still be going strong.
Euphorbia polychroma (Zone 4) is the epitome of all the springtime spurges. Its glowing flower heads light up the surrounding area like so many beacons among the spreading verdancy. It is happy in dappled shade, as in this association, or in the open. A native of central Europe, it occurs naturally in scrub and woodland margins, so is happy living cheek by jowl with neighboring plants. Despite its short stature, seldom over a foot tall, it has enormous presence. All eyes are on it in April, May, and June. During summer its bracts quiet down, becoming green and soft orange. It needs soil that doesn’t dry out, with plenty of humus incorporated at planting time and a mulch with similar material. Where there is competition from tree roots, spot water during dry spells.
Elders are easy to grow in any moisture-retentive soil. Although most will reach large proportions, they can be accommodated in smaller gardens by coppicing their growth every second year. Even shrubs chopped back to ground level will make five to six feet of growth in a season and will produce flowers the same year. Both flowers and leaves are bigger and better on coppiced specimens. Sambucus nigra ‘Thundercloud’ (Zone 5) has glorious polished bronze leaves and unexpectedly pink flowers in frothy heads.
Tulipa ‘Prinses Irene’ (Zone 4) is one of my favorite tulips—sturdy and unfazed by blustery spring weather. But it is the coloring that instantly attracts: vivid orange globes over glaucous foliage and purple-blue stems make for an instant wow factor. The stem color suffuses with the petal color, with a touch of pink for good measure, and when the sun shines bright the flower’s enclosed secrets are revealed.
(1) Euphorbia myrsinites; (2) Eryngium bourgatii ‘Blue Form’; (3) Primula auricula ‘Old Mustard’; (4) Sedum ‘Stewerd Rhubarb Mountain’; (5) Stipa tenuissima
Plants chosen for their suitability to specific conditions seem to harmonize effortlessly. On a dry, sun-baked site, Euphorbia myrsinites tumbles down a dry stone wall, backed by tough characters that enjoy sunbathing and tolerate drought. Their thick glaucous foliage, combined with the mobile hairfine blades of the stipa, evoke the image of a Turkish hillside or the smell of a dry Mediterranean maquis. The coloring of the group is close and subtle, restricted to warm ochres and yellows and gray-blues. Later, the eryngium will contribute prickly flower bracts that gradually turn a deep blue, while the sedum will burst into clouds of lemon and gray-pink flowers, topping the solid structure of its heavy stems.
Euphorbia myrsinites (Zone 5) is a low-growing spurge with thick stems, clothed with succulent blue-gray leaves. Its prostrate habit evolved to cope with exposure both to sun and drying winds in its natural habitat in mountainous regions of southern Europe and western Asia. It thrives on poverty and neglect and, despite its origins, can withstand low winter temperatures on sharply-drained soils. The flowering stems push forward from the low mounds of foliage in early spring, extending in all directions. This makes it a perfect candidate for banks or walls. The bracts are citric yellow, changing gradually to a warmer, softer yellow occasionally touched with orange.
Eryngium bourgatii‘Blue Form’ (Zone 5) contributes to the garden picture all year. Its prickly, much-divided leaves add textural interest, emphasized by white veining, as though someone had poured mercury onto the leaves. The equally spiny bracts are outstanding, particularly when the whole flower stem and inflorescence are imbued with brilliant blue. It needs good drainage but will thrive even on clay soil with the addition of plenty of grit or gravel.
Primula auricula ‘Old Mustard’ (Zone 2) is an old variety that responds well to garden cultivation. Its leaves, stems, and flowers are covered in farina, giving it the look of one of the show auriculas. In fact, it is very close to the wild species, which clings to rock faces on south-facing slopes in its native European Alps. It loves alkaline soil as crunchy as possible (add grit or gravel at planting time). It will flourish in a sun-baked bed or can be planted on its side in between the stones of a dry stone wall.
Some plants really do remind you of culinary treats. The aptly named Sedum ‘Stewed Rhubarb Mountain’ (Zone 5) is a stocky plant that seldom flops, providing it isn’t overfed. Its attractive glaucous leaves take on tinges of pink as summer progresses, and are later crowned in the fall by large, globular heads of pink buds opening to greenish yellow flowers.
Stipa tenuissima (Zone 6) is one of the softest, waftiest grasses around, bringing movement and light into static plantings. Although it is theoretically evergreen, older blades turn to biscuit, and the soft inflorescence is the same color, giving the whole tussock a pale and interesting persona. Old growth should be removed by pulling it gently from the base. H