Purple wood spurge is an evergreen perennial favored for its purple-tinged, dark green leaves. The foliage retains some color during the wintertime, so the plant can be considered a "winter interest" specimen in areas that don't receive much snowfall (where there is heavy snow, these low-level plants may be buried for much of the winter). Wood spurge is easy to care for and is deer-resistant, but it is also toxic to humans.
Taxonomy and Type
According to plant taxonomy, purple wood spurge is categorized as Euphorbia amygdaloides 'Purpurea.' The cultivar name 'Purpurea' describes the color of the plant's leaves. Other common varieties include:
- Leatherleaf spurge (Euphorbia amygdaloides var. robbiae)
- Cushion spurge (Euphorbia polychroma)
- Mole plant (Euphorbia lathyris)
The word "spurge" is related to "purge" and refers to the plant's traditional medicinal use as a laxative, or "purgative." While Euphorbia amygdaloides 'Purpurea' is, technically, an evergreen plant, its vegetation can suffer considerably during an average winter in colder climates, such as USDA plant hardiness zones 4 and 5.
The growth of purple wood spurge can vary significantly, but the typical size at maturity is 12 to 18 inches tall, with a spread of about twice the height. The stems are ringed by leaves, the beauty of which is the main reason gardeners choose to grow this perennial. Its foliage is dark enough to quality Euphorbia amygdaloides 'Purpurea' as one of the so-called black plants.
Wood spurge typically blooms in early May. Note that what makes the inflorescence noteworthy is not the actual flowers (which are yellow but insignificant) but rather the accompanying chartreuse bracts. Clusters of these appear atop the plant's red stems, which provide eye-catching contrast for the light green bracts.
The new foliage of purple wood spurge is lighter in spring (red to burgundy) than what follows. It is also lighter than any old leaves. The coloration after the initial leafing out becomes a deep purple-green. The stems start out red, although they lose this coloration in summer. Likewise, the leaves become progressively more green as summer advances. By August, the leaves are totally green and darker than the coloration on most green plants.
The foliage becomes a very dark purple-green again in the fall. By November, in some years, there may be an interesting pinkish-red on the bottom leaves, while the rest of the leaves assume a purple color. If December is cold (in zones 4 and 5), the stems of wood spurge may start to droop over, and this deterioration eventually spreads to the leaves. In warmer areas (and during relatively warm winters in zone 5), much of the foliage should remain healthy and assume a black-purple color that is quite alluring.
Sun and Soil Requirements
Grow this dark-leaved perennial in well-drained soil of average fertility and in full sun to partial shade. Full sun can improve the leaf color.
Uses in Landscaping
Toxicity Warning (and Benefit)
Euphorbia amygdaloides 'Purpurea' is a poisonous plant. Once you are aware that these plants are related to Christmas poinsettias (Euphorbia is a huge genus), their toxicity should come as no surprise. Many people have an allergic reaction to poinsettias. Both wood spurge and poinsettia exude a milky, white sap when damaged.
The latex in purple wood spurge can irritate the eyes and skin upon contact. It is also poisonous to eat. Parents of small children should think twice about growing this perennial if the children will be spending any time in the yard without vigilant supervision.
The flip side of purple wood spurge's toxicity is that it is a deer-resistant perennial; deer know better than to eat a poisonous plant. Rabbits and various other pests reputedly won't eat it, either.
Pruning and Cleanup
Purple wood spurge is not especially amenable to pruning, nor is pruning usually necessary since it's not a large plant. If you do prune it, don't expect re-growth to occur quickly.
Furthermore, the plant blooms on the previous year's growth, so if you decide to prune (and if you value the flowers), wait until after the blooming period. Under some conditions, the plant may get leggy enough that you might want to prune it to restore compactness.
Cleanup is a separate issue from pruning. For best appearance, cut off the flower stalks in June after they dry out and become less attractive. In spring, in cold climates, you also might remove damaged portions of stems that have succumbed to the winter cold.
Purple wood spurge readily self-sows, so unless you want it to spread, you'll probably have to pull new seedlings continually. Divide the plant in early spring to prevent overcrowding, if necessary.