Euphorbia (Spurges)

Euphorbia is a very large genus with over 2,000 species, part of the Euphorbiaceae family whose members include surprising shapes and sizes. They can be annuals, perennials, evergreen or deciduous, even shrubs or trees. Most originated in Africa, Madagascar, and the Americas and do quite well in temperate zones worldwide including the Mediterranean climate in Sonoma County. 

Common and Uncommon

The common holiday plant, poinsettia, is Euphorbia pulcherrima. With showy, bright red bracts, it looks a bit different than most of its fellow species—often called spurges—grown in local gardens.

• Almost all euphorbias are relatively easy-care perennials that are either evergreen or die down to the ground in winter and come back in spring.
• Leafy-stemmed foliage comes in many colors, sizes and textures.
• Various perennial species may appear as mounds, clusters of upright stems, or low ground crawlers. 
• Flowering occurs from early spring thru early summer, then continues to provide beautiful foliage throughout the growing season or even year round. 
• Many are drought tolerant, deer and gopher resistant.
• One of the more unusual aspects of Euphorbia is its blossoms. 
  • What is mistakenly called a flower is technically a cyathium, consisting of fused bracts that form a cup around a very small, true flower. Bunches of leaf-like bracts grow on the ends of the leafy stems and are frequently brightly colored—chartreuse in many species—creating a stunning display. 
• Leafy stems are also attractive, varying from blue, blue-green, reddish-green, to reddish-orange and green tinged with purple.

Care

Planting requirements for euphorbias vary depending on the species. Many require full sun, but some can tolerate partial shade, and a few can even handle full shade. 

• Most species suitable to Sonoma County thrive in heat and can also take some frost.
• They can be drought tolerant, but some need regular water and almost all dislike soggy feet. Consult nursery tags for care of each species.
• Despite the many redeeming features of euphorbias, they have some drawbacks.
  • All have a milky white sap in their stems that is irritating on contact, can be toxic if ingested and especially painful if it gets into the eyes. 
  • It’s important to use care when cutting stems and to wash up quickly after pruning. Gloves and long sleeves help protect hands and arms.
  • The unappetizing sap keeps deer and gophers away.
  • Self-sowing and spreading by underground stems can also be bothersome, but unwanted plants are easily pulled up.

Selected species

Euphorbias described below focus on perennial plants for Sonoma County gardens. For a discussion of succulent euphorbias, see our article on succulents.   

• Euphorbia amygdaloides robbiae. This species can become an undesirable and invasive nuisance unless it is strictly contained on all sides; then, it is an easy-care plant needing little attention. Commonly called Mrs. Robb’s bonnet, single or double-stemmed plants are fairly short, to 1 ft. tall. They can tolerate more shade than most euphorbias and can be a useful variety where there is no supplemental summer irrigation. Greenish yellow flow clusters bloom at stem tops.
• Euphorbia characias. The hallmark of this species are the clusters of brilliant chartreuse/lime green flower heads that appear in late winter to early spring and last for many weeks. c. wulfenii has the largest and most stunning flower heads and is the most commonly grown form of this species. Evergreen, upright stems crowded with narrow blue-green leaves grow in a dome shape to about 4 ft. Stems should be cut back to the base as seed heads develop to prevent unwanted self-sowing and to allow room for new shoots that have already starting growing. It loves full sun and requires little water.
• Euphorbia griffithii. This native of the Himalayas looks very different from the other species listed. It grows as an erect stem to 3 ft. tall and spreads slowly by creeping roots. ‘Fireglow’ has vibrant orange-red bracts that appear in early summer and create a sea of color and interest in full sun or filtered light where it enjoys moderate moisture. Cut back to the ground in winter and divide every 3-4 years or more often to contain spread and keep it under control. Some gardeners prefer the similar ‘Fern Cottage’ cultivar that is said to be less invasive.
• Euphorbia x martinii. A hybrid of characias and E. amygdaloides, this perennial reaches 2-3 ft. high and wide, and has dark green leaves tinged with a bit of purple. Dense clusters of chartreuse flowers with dark centers appear at branch tips in late winter to spring. It likes full sun or part shade, is drought resistant, and does not reseed as much as other species. ‘Ascot Rainbow’ is topped with variegated foliage.
• Euphorbia myrsinites. Commonly called myrtle spurge and donkey-tail spurge, this charming evergreen species has stems that trail on the ground octopus–like, outward from the crown. Short, chunky blue-green leaves swirl around the stems and end in clusters of chartreuse bracts in early spring, adding eye-catching allure to the landscape. Rather than deadheading individual flowers, cut entire stems back to the base taking care not to remove slowly emerging replacement stems. New growth will continue year round. Some gardeners remove entire plants after flowering, allowing seeds to fall and self-sow for new plants and blooms the following year.

August 2023