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Mendocino Coast Botanical Gardens, 47 acres of botanical bliss fronting the Pacific Ocean

Euphorbias

Unusual plants for the garden!

Botanical Name: Euphorbia spp. Common Name: Spruge Family: Euphrobiaceae 

Description: Euphorbiaceae is a huge genus containing more than 2,000 species including trees, shrubs, perennials, succulents, biennials, and annuals. Most familiar is the popular poinsettia (Euphorbia pulcherrima), sold as potted plants. The flowers have no petals or sepals. What appear to be flowers are actually part of the leaf structure called a bract. Nestled in the center of each cuplike bract is a tiny nectary and the male stamen and female ovaries or pistils.

Cultivation: This entry will concentrate on herbaceous (non-woody) euphorbias also called garden spurges. Many euphorbias are drought tolerant Mediterranean perennials which thrive in full sun and well-drained soil. Some species tolerate clay soil and woodland species have evolved under a tree canopy of dappled or partial shade. All euphorbias need good drainage. Drainage can be improved by adding organic material in the form of aged manure, compost, or bagged commercial soil conditioner and mounding the soil up to create a small berm or hillock to plant on. Euphorbias are a favorite with landscape designers because they combine elegant form, interesting foliage, and in mid spring each stem is crowned with long lasting corollas of bright chartreuse. These plants can be thought of as the little black dress of the garden. With their mounded bushy form and stems cloaked in narrow lanceolate leaves, they pull the look of a garden together and make every plant around them show off to its best effect. Except for the Euphorbia griffithii varieties, which being deciduous put on a show of changing fall colors, euphorbias benefit from having their stems cut at the base of the plant when the flowers are looking spent and the foliage starts to yellow slightly. The broken stems exude a milky sap (latex) which can be a skin irritant so it is important to wear gloves while performing this chore and to protect your eyes. Children should be prevented from eating this plant as it is toxic. The sap also gums up pruners which will need to be cleaned after working with euphorbias. The inconvenience of this task is offset by the thought that the sap is what makes euphorbias less than tasty to deer. While they are avoided by insects, voles, and gophers, euphorbias in damp areas can be vulnerable to powdery mildew. If you have very wet spring weather or summer fog, air circulation around plants becomes important. In these cases, do not plant too closely. Some euphorbias such as Euphorbia characias will self-seed readily. E. esula (leafy spurge) and E. lathyris (caper spurge) are spreading into wild areas in parts of California.

Species and cultivars that do well on the Mendocino Coast

Euphorbia characias ssp. wulfenii is a stately plant that can be used as a blender or as an architectural specimen. It forms 3 to 4 foot wide bushy mound with 3 to 4 foot stems sporting narrow, blue-gray leaves. In late spring the stems are topped with large (6" by 9") cylindrical clouds of glowing apple-green. E. characias can handle clay better than other varieties but it is important not to over water. This euphorbia combines quite nicely with red-leafed leucadendrons or purple flowered anything.

Euphorbia amygdaloides 'Purpurea' or 'Rubra' commonly called wood spurge, is a smaller (2' by 2') plant with reddish stems and red glowing tips. The dark green foliage has reddish purple undersides that deepen to purple as the season progresses. This rubescent coloring makes a stunning contrast to the acid green bracts which are eagerly anticipated by gardeners in early spring.

Euphorbia martini is a cross between E. characias and E. amygdaloides. It has a somewhat narrower profile than its E. characias parent. Its dark foliage is tinted red when young. An interesting effect is created during the bloom time by maroon nectaries which make contrasting dots of dark color in the center of each chartreuse bract. Moving to the warmer side of the color spectrum there are a handful of varieties of Euphorbia griffithii which come from the cool climates of Bhutan and south-east Tibet. Found in the wild in mixed pine, oak and rhododendron forest, these deciduous and slowly spreading plants tolerate partial shade. Their red stems, olive green leaves suffused with orange tones, and burnt orange to burnt apricot bracts partner well with weeping orange tinted foliage of New Zealand sedge (Carex tenuiculmis).

Resources: Euphorbia: A Gardener's Guide" by Roger Turner http://ucce.ucdavis.edu/datastore/datareport.cfm?reportnumber=338, article entitled "Euphoric Over Euphorbias" Fine Gardening Magazine, February 200

Submitted by Master Gardener Lynne Abels, 2007.