Large genus of about 2,000 species. What is called a flower is technically a cyathium, which consists of fused bracts that form a cup around the much-reduced true flowers. Cyathia may appear singly or in clusters. In some cases, as with poinsettia (E. pulcherrima), additional bracts below provide most of the color. Fruit is usually a dry capsule that releases seeds explosively, shooting them up to several feet away. Many euphorbias are succulents; these often mimic cacti in appearance and are as diverse in form and size. Only a few succulent types are listed here, but specialists in cacti and succulents can supply scores of species and selections.
All euphorbias have milky white sap that is irritating on contact or toxic if ingested (degree of irritation or toxicity varies, depending on species). Before using cut flowers in arrangements, dip stems in boiling water or hold in a flame for a few seconds to prevent bleeding sap.
Give these plants well-drained soil. Deer don't care for them.
E. amygdaloides. WOOD SPURGE. Perennial. Zones US, MS, LS, CS; USDA 6-9. From Europe and Turkey. To 3 ft. tall, 1 ft. wide, with reddish green stems. Evergreen, 1- to 3-in.-long, dark green leaves have red undersides that turn darker red in winter. Greenish yellow flowers in clusters to 8 in. long at stem ends in late winter to early spring. Best in sun but tolerates some shade. 'Purpurea' has heavily purple-tinted foliage, bright green inflorescences.
E. a. robbiae. MRS. ROBB'S BONNET. Zones US, MS, LS, CS; USDA 6-9. Shorter than the species, usually under 1 ft. high. Pale, lime-green flower clusters. Spreads slowly but surely from underground rhizomes. Can thrive in sun (but not hottest afternoon sun) and in deep shade. Regular to little water.
E. biglandulosa. See E. rigida
E. characias. Perennial. Zones US, MS, LS, CS; USDA 6-9. Mediterranean native. Upright stems crowded with narrow, blue-green leaves form a dome-shaped bush 4 ft. high and wide. Chartreuse or lime-green flowers in dense, round-to-cylindrical clusters appear in late winter, early spring. Color holds with only slight fading until seeds ripen; then stalks turn yellow and should be cut out at base, since new shoots have already made growth for next year's flowers. 'Glacier Blue' grows just over a foot high and has blue-green leaves edged in cream. 'Humpty Dumpty' is a shorter (to 2-ft.-high), vigorous selection. E. c. wulfenii (E. veneta), a commonly grown form, has broader clusters of yellow flowers. All are fairly drought resistant and perform best in full sun.
E. cotinifolia. CARIBBEAN COPPER PLANT. Shrub or tree. Zones TS; USDA 10-11. From tropical America. Usually grown as an annual to add colorful foliage to a summer border, though it can become a small tree to 18 ft. tall if grown in a warm, frost-free spot. Long-stalked leaves to 4 in. long, 3 in. wide, usually borne in threes, are similar to those of smoke tree (Cotinus); 'Atropurpurea', the form most commonly grown, has wine-red leaves. Loose flower clusters have small white bracts, are not showy. Likes full sun, heat, good drainage; can't take frost.
E. dulcis 'Chameleon'. Perennial. Zones US, MS, LS, CS; USDA 6-9. Forms a mound to 2 ft. high and wide. New spring growth is burgundy, maturing to dark bronzy green. Greenish yellow flower heads with a purplish tint appear at stem ends in early summer. Leaves and bracts turn rich purple in fall. Spreads by self-sowing; comes true from seed. Full sun. Tolerates dry soil.
E. epithymoides. See E. polychroma
E. griffithii. Perennial. Zones US, MS, LS, CS; USDA 6-9. Erect-stemmed Himalayan native to 3 ft. tall and wide; spreads by creeping roots but is not aggressive. Narrow leaves are medium green, tinged with red when they emerge. Reddish orange-to-red bracts in early summer; those of 'Fireglow' are vivid orange-red. Dies back in winter. Full sun or light shade.
E. hypericifolia. Perennial in Zones TS; USDA 10-11. Annual anywhere. Delicate, airy mounds to 1218 in. high and nearly as wide. Small white flowers look like snowflakes interspersed with the sparse, olive-green foliage. Plant resembles baby's breath (Gypsophila paniculata). Blooms year-round in mild winter areas, spring to fall elsewhere. Excellent in pots and hanging baskets. 'Diamond Frost' and 'Euphoric White' are popular and dependable. 'Breathless Blush' has leaves and flowers flushed in deep pink. Full sun to partial shade.
E. lathyris. MOLE PLANT, GOPHER PLANT. Biennial. Zones US, MS, LS, CS; USDA 6-9. From Europe, northwest Africa. Legend claims that it repels gophers and moles. Stems have poisonous, caustic, milky juice; keep away from skin and especially eyes, as painful burns can result. Juice could conceivably bother a gopher or mole enough to make it beat a hasty retreat. Single-stemmed plant to 5 ft. tall and 1 ft. wide. Stem is densely set with large leaves growing at right angles to the stem and to each other (forming four longitudinal rows along stem). In second summer, produces short-lived cluster of unspectacular yellow flowers at top of stem. Flowers soon go to seed, after which the plant dies. Start from seed; plant will keep going by self-sowing. Sun or shade. Little to regular water.
E. marginata. SNOW-ON-THE-MOUNTAIN. Annual. Zones US, MS, LS, CS, TS; USDA 6-11. From central North America. To 2 ft. high, 1 ft. wide. Oval, light green leaves; upper ones are striped and margined white, sometimes even solid white. Summer flowers are variegated in green and white. Good for contrast with bright-colored dahlias, scarlet sage (Salvia splendens), zinnias, or with dark-colored plume celosia. Sow seeds in place in spring, in sun or partial shade. Thin to only a few inches apart, since plants are somewhat rangy.
E. milii. CROWN OF THORNS. Woody shrub; evergreen but sparsely leafed. Zones CS, TS; USDA 9-11; or indoor, greenhouse, or summer potted plant. Some frost damage below 28F. From Madagascar. To 14 ft. high, 1 ft. wide. Stems armed with long, sharp thorns. Roundish, thin, light green leaves are usually found only near branch ends. Clustered pairs of bright red bracts put on a show all year. Many selections and hybrids, varying in form, size, and bract color (red, white, yellow, orange, pink). Thai Giant hybrids feature much larger flowers in red, pink, yellow, and sometimes multicolor. 'Red Jillian', for example, has 2-in. red flowers with accents of bright green. Train on small frame or trellis against a sheltered wall; or grow in container. Salt tolerance makes it an ideal choice for seaside plantings. Grow in porous but not rocky soil, in full sun or light shade. Indoors, give bright light, regular water (less in winter); feed with half-strength general-purpose liquid houseplant fertilizer once a week in spring and summer.
E. myrsinites. SPURGE. Perennial. Zones US, MS, LS, CS; USDA 6-9. Native from southern Europe to central Asia. To 6 in. high, 1 ft. wide. Evergreen plant with stems that trail outward from central crown, then rise toward tips. Stiff, roundish, blue-gray leaves set closely in spirals around stems. Flattish clusters of chartreuse-to-yellow flowers top stem ends in late winter, early spring. Cut out old stems as they turn yellow. Withstands cold, heat, and aridity but is short lived in warm-winter areas. Use in sunny rock garden with succulents and gray-leafed plants.
E. polychroma. CUSHION SPURGE. Perennial. Zones US, MS, LS, CS; USDA 6-9. From Europe. Neatly rounded hemisphere to 1 ft. high, 2 ft. wide, with deep green leaves symmetrically arranged on closely set, hairy stems. From midspring to midsummer, plant is covered with rounded clusters of bright yellow flowers surrounded by whorls of yellow-green bracts. Effect is of a gold mound suffused with green. Displays good fall color (yellow to orange or red) before going dormant. 'Bonfire' has leaves that emerge green but mature to red and hold their color all summer. 'Lacy' has white-variegated leaves. Use in rock gardens, perennial borders. Needs some afternoon shade in Lower and Coastal South. Short lived but reseeds.
E. pulcherrima. POINSETTIA. Evergreen, semievergreen, or deciduous shrub. Zones CS (protected), TS; USDA 9-11 or indoors. Native to Mexico. Leggy plant to 10 ft. or taller, 6 ft. wide. Coarse leaves grow on stiffly upright canes. Showy part of plant consists of petal-like bracts; true flowers in center are yellowish and inconspicuous. Red single form is the most familiar; less well known are double-bracted red sorts and forms with white, yellowish, pink, or marbled bracts. 'Winter Rose' has unched, curled bracts that resemble rose blooms and come in several colors; make excellent cut flowers. Plants bloom only when they experience long nightsin winter and into spring. To get potted plants to bloom, starting in October, put them in a closet (no light at all) each night for 14 hours, then move them into light in the morning for a maximum of 10 hours. Continue this procedure for 10 weeks; you can have poinsettia blossoms by Christmas. Bracts of paler kinds often last until later in spring. Milky sap is not poisonous; most people find it either completely harmless or at most mildly irritating to skin or stomach.
Useful garden plant in well-drained soil and full sun. Where adapted outdoors, needs no special care. Grow as informal hedge in the Tropical South; in the Coastal South, plant against sunny wall, in sheltered corner, under south-facing eaves. Plants grown outdoors in the Coastal South are likely to die down in winter. Thin branches in summer to produce larger bracts; or prune them back at 2-month intervals for bushy growth (but often smaller bracts). To improve red color, feed every 2 weeks with high-nitrogen fertilizer, starting when color begins to show.
Unlike their predecessors, modern poinsettia selections retain their foliage well into spring if given reasonable light. To care for holiday gift plants, keep them in a cool, well-lit room until after the last frost. Avoid sudden temperature changes; keep soil moist, but don't let water stand in pot saucer. When frost danger is past, cut back stems to two buds and set plants out in garden; or keep them in containers in a sunny spot on the patio. Potted plant will probably grow too tall for indoor use the next winter but may survive winter if well sheltered. Start new plants by making late-summer cuttings of stems with four or five eyes (joints).
E. rigida. Perennial. Zones LS, CS, TS; USDA 8-11. Mediterranean native forms a 3- to 5-ft.-wide clump of stems that angle outward, then rise up to 2 ft. high. Fleshy, gray-green leaves to 1 in. long are narrow and pointed, their bases set tightly against stems. Broad, domed flower clusters in late winter or early spring are chartreuse-yellow, fading to pinkish. After seeds ripen, stems die back and should be removed; new stems take their place. Reseeds in mildest-winter areas, but not enough to become a pest. Showy display plant in borders, rock gardens, containers. Full sun. Tolerates drought.
E. robbiae. See E. amygdaloides robbiae
E. tirucalli. MILKBUSH, PENCIL CACTUS, PENCIL TREE. Succulent tree or shrub. Zones TS; USDA 10-11; or indoors. From tropical eastern Africa. Grown for striking pattern of silhouette or shadow. Fast growing to possible 30 ft. tall and 6 ft. wide, usually much smaller. Single or multiple trunks support tangle of light green, pencil-thick, succulent branches with tiny leaves present only on actively growing tips. Flowers are unimportant. 'Sticks on Fire' has pale pink to fiery salmon-pink stems; new growth has the most intense color in bright light. Both species and selections are very tolerant of seacoast conditions. Full sun. Keep milky sap away from eyes, as it can cause severe damage. As houseplant, thrives in driest atmosphere; needs plenty of light, well-drained potting mix, routine watering and fertilizing.
E. veneta, E. wulfenii. See E. characias