Plant of the Month — Euphorbia Print
Monday, 15 November 2010 00:00

Euphorbia myrsinites (Donkey-tail Spurge)
Euphorbia, one of the about 300 genera to be found within the family Euphorbiaceae, is often overlooked as a herbaceous perennials in North America since most of the over 2,000 species within Euphorbia are tropical or subtropical in origin. The ubiquitous (in November/December) Poinsettia (E. pulcherrima) is perhaps the most well known of the genus but with so many species there is an extreme amount of diversity. There are several species of more temperate origin that can add interest and variety to our colder landscapes.

Euphorbia is commonly known as spurge due to the historical use of sap as a purgative. Ingestion is not recommended. Toxicity will vary between species and genera with the Poinsettia not being toxic but causing mildly uncomfortable symptoms to those unwise enough to eat it. The milky sap can cause skin irritation to susceptible people (especially those sensitive to latex) and a sticky annoyance to everyone else. Nevertheless, these are valuable plants for both gardens and containers.

Euphorbia polychroma (Cushion Spurge)
Euphorbia amygdaloides ‘Purpurea’ (Wood Spurge)
Euphorbia dulcis ‘Chameleon’ (Chameleon Spurge)
Euphorbia griffithii ‘Fireglow’ (Griffith’s Spurge)
The feature that ties all Euphorbia together is their unusual and unisexual flowers. Typically they are not particularly conspicuous or attractive and are grouped into specialized inflorescences called cyanthia which are then often surrounded by spectacularly showy and colorful bracts. The fruit are usually capsules that are ‘explosively dehiscent,’ that is they open suddenly and violently to expel their seed relatively great distances. This explains the establishment of volunteer spurge in parts of the landscape that the gardener did not necessarily intend, but will often prove to be to their liking. This is not to say that Euphorbia are invasive, just that they are ‘open to exploratory missions.’ They are easily removed if unwelcome.

Typically Euphorbia prefer a well-drained, even poor soil, in a full sun or perhaps slightly shaded location. They are drought tolerant once established. Rock gardens, walls, screes and dry containers are all ideal. Winter wetness will usually prove fatal, but otherwise these are easy plants to grow both in the nursery and in the landscape. Usually bypassed by herbivores such as deer and rabbits, and most other pests and diseases, but not overly useful as a cut flower.

E. myrsinites
Donkey-tail Spurge
Somewhat controversial with friends and opponents and very few with ambivalent feelings. Proponents expound on the lovely blue gray foliage that spirals around the sprawling or trailing stems and brilliant chartreuse bracts surrounding the yellow flowers during spring. Many also enjoy finding specimens in unexpected areas of the garden. Adversaries deplore this same propensity to self seed. Although evergreen they do tend to look a little rough in the early spring until a fresh flush of growth appears. Additionally E. myrsinites has proven useful in vegetated roofs as a good companion to low growing Sedum. Height: 6”-8” (15 – 20cm), Spread: 18”-24” (45-60cm) fast growth rate. USDA 5-9

E. polychroma
Cushion Spurge
Beautiful mounding plants that are wonderful garden features in the late spring to early summer when the bracts are showing color, and excellent fillers for the border during the rest of the year. Brilliant screaming yellow bracts when lots of color is welcome and then again in the fall with cooler weather adding a reddish tinge to the foliage. Easy to grow in poor soils and sun to part shade. Will self seed to some degree but not as much as E. myrsinites. Height: 12”-18” (30-45cm) Spread: 18”-24” (45-60cm). Moderate growth rate. USDA 4-8

E. amygdaloides ‘Purpurea’
Wood Spurge
As the name implies, this selection has lovely purple black foliage, which is a great contrast to the chartreuse bracts in the spring. This selection is quite happy in a partially shaded or woodland situation. In areas with colder winters, longevity may prove an issue but there are usually seedlings making an appearance so total loss is rare. Flowers form on old growth so any required pruning should take place just after flowering, bearing in mind that this will preclude seeding for that year. Height: 12”-18” (30-45cm) Spread: 18”-24” (45-60cm). Fast growth rate. USDA 5-9

E. dulcis ‘Chameleon’
Chameleon Spurge
Aptly named as the foliage changes throughout the year as the plant matures, beginning with shades of purple, developing rich burgundies and then deeper reds as the weather cools again. Yellow bracts surround the inconspicuous greenish flowers but the effect is somewhat more subtle and refined as there are distinct tinges of purple to lessen the contrast. Interestingly, seedlings are usually true to form although not overly abundant. A garden worthy plant especially in areas with limited space where every plant must pull its weight at all times. Height: 12”-18” (30-45cm) Spread: 18”-24” (45-60cm). Fast growth rate. USDA 4-9

E. griffithii ‘Fireglow’
Griffith’s Spurge
Dark green foliage with a prominent red midrib forms a bushy mound. New growth has a lovely bronzy red glow reminiscent of embers, however the real fire comes from the bright orange-red bracts that begin to appear in early summer and continue through to early fall when the foliage ignites into a blaze of bright red glory. Easy to grow, but may be slow to establish. Not prone to much self seeding but may need to be restrained from rhizomatous spreading.
This is an older selection that is unfortunately becoming unfashionable due to the overwhelming availability of newer cultivars (of Euphorbia and others), but worth searching for. Height: 24”-36” (60-90 cm) Spread: 24”-30” (60-75cm) Slower growth rate. USDA 4-9.
 

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