Most gardeners and nongardeners know of the genus Euphorbia, the spurges. Perhaps the most widely known of the approximately 2,000 species worldwide, is the one that shows up with the “holiday season,” poinsettia. Bright red bracts obscure the actual flowers with their showy color.
Then there are the gardeners with gopher problems who have used gopher plant, another Euphorbia, as a method of control. It may be so, but this Euphorbia is a rampant spreader and may soon become more of a pest than the one it targeted!
Evergreen Euphorbia worthy of adding to your landscape are a select few commonly sold in local nurseries, especially in the spring.
The evergreen Euphorbia suited to our climate are excellent deer-resistant landscape plants, but all have a milky white sap within the stems and even the leaves.
This can be irritating to skin on contact, but brushing up against the leaves in the garden will not do it.
Most of the evergreen spurges are tidy subshrubs (small shrubs) that do not spread. The largest is Euphorbia characias at four-foot height and spread. A substantial evergreen! I observed one foothill garden where the owners had allowed the plant to spread by seed, consuming a large sunny area of poor soil.
While striking in bloom with chartreuse flowers, I prefer the artistic statement made with a single specimen.
The foliage of E. characias is blue-green, a color heightened if you are growing blue flowers near it. Grown near a blue wall intensifies the hue as well. Or consider planting it in or near a large blue container. Have fun with subtle color echoes.
While the Euphorbia are not high in water demands, E. characias is the most water-efficient. A mature plant, mulched, will adjust to irrigation every three weeks.
As for any plant, watering schedule is based on the amount of compost in the soil, the natural phosphorus for strong root development, the age of the plant, and the material used for mulch.
A more modest evergreen Euphorbia is E. x martinii, at two- to three-foot height and spread.
Genetically, this spurge is related to E. characias, with the same bright chartreuse flowers. Stems have a purple-red coloring, and the cultivar ‘Red Martin’ has more red on the stems and new spring growth.
A new plant available in the trade in recent years is Euphorbia ‘Black Bird.’ Because it has been a patented cultivar, supplies have been limited, but I have been able to find it in the local nurseries occasionally.
This is an outstanding selection, with rich purple-red foliage and flowers.
The actual blossom has a touch of the chartreuse typical of Euphorbia flowers. It is always the bracts that have the stronger coloration of the leaves.
‘Black Bird’ is about three feet in height and spread, adding a striking focal point in a sunny location. With snow on the ground, the color of this evergreen is dynamic.
The foliage of the variegated cultivars, ‘Silver Swan’ and ‘Glacier Blue’ is white and light-green with a blue undertone. Unlike many variegated plants, they are very tolerant of sun exposure.
However, they will also do well in partial shade. Too much shade and they will be reaching for the light rather than forming the beautiful three-foot high and wide mound that is their nature.
In my garden ‘Silver Swan’ is growing near spangle grass (wild sea oats, bamboo grass), Chasmanthium latifolium, its graceful summer into fall seed heads draping over the spurge.
One winter heavy snow broke most of the strong stems of ‘Silver Swan.’
I pruned it back to about one foot and it has recovered beautifully. When I prune I wear gloves to avoid the caustic sap.
An evergreen Euphorbia that is a very strong spreader is Mrs. Robb’s bonnet (Euphorbia amygdaloides ssp. Robbiae).This is a perfect groundcover for shade and semi-shade.
If mature sections show any sign of weakening, which may be a sign of over-watering or too much sun, prune them back to the ground and spread compost.
Be attentive to the individual sun requirements of each cultivar and species as you select the perfect Euphorbia for your garden.
Carolyn Singer has gardened organically in Nevada County since 1977. She will teach Foothill Gardening 101, from 9:30 to 11:30 a.m. Dec. 8 at Peaceful Valley Farm & Garden Supply. For a class description and more information about foothill gardening, visit http://www.carolynsingergardens.com.
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