Download Euphorbias at RBG - The Ruth Bancroft Garden

EUPHORBIAS AT RBG
Euphorbia caput-medusae [Medusa-head Euphorbia]
BED B
One of a group of Euphorbia species, mostly native to South Africa, which have a globular central “head”
and radiating cylindrical arms. These are collectively known as the “medusoid euphorbias”. Our large
plant of E. caput-medusae is along the North Drive, at the northwest corner of bed B. The other
medusoids are grouped in bed 5A and the adjacent side of beds 4 and 5. While we started out with
several true species in this area, over the years they have hybridized and come up from seed, so that now
we have mostly hybrids. Their flowers come in shades of white, yellow and green.
Euphorbia clava
BED 7
Native to the southern part of South Africa, this species has bumpy cylindrical green stems with long
narrow leaves on the upper part. It can reach a height of about 3 feet. The green flowers are held well
above the top of the plant on slender stalks. There is a group of these in the southeast part of bed 7.
Euphorbia coerulescens
BED 7
This South African species forms clumps of blue-green branching stems which can reach 4 or more feet
in height. The stems are faceted, with a horn-like strip running between the facets. Pairs of sharp spines
protrude from this strip. There are constrictions along the stems, marking the divisions between the
growth from successive years. The small yellow flowers are followed by rounded-triangular red seed
pods. This plant is found in the middle of the eastern part of bed 7.
Euphorbia horrida
BED 5
This belongs to another group of South African species, which have cylindrical bodies and spines which
are formed from the persistent old flower stalks. E. horrida is usually gray to powdery-white in color, but
some of the other species in the group are green. The small flowers may be dark red, yellow or greenish.
Sometimes these plants may remain single, but usually they put out shoots from the base to form clumps.
Several forms are planted in bed 5.
Euphorbia grandicornis [Cow’s Horn Euphorbia]
BED 1A
This species and its relatives (including hybrids such as ‘Zig-Zag’) grow large enough to eventually
become trees, though our climate is too cold to achieve this. E. grandicornis has stems with prominent
“ribs” which are edged with tough horn-like margins bearing pairs of sharp thorns. Its fierce armature
leads many people to assume that it is a cactus, but its small yellow flowers show its true affinity to the
other euphorbias. Look for some cow’s-horn euphorbias along the fence in bed 1A.
Euphorbia milii [Crown-of-Thorns]
E. SHADE HOUSE
This species is one of many from Madagascar with cylindrical succulent stems and oval to strap-like
leaves. Though its flowers are small and yellow, they are cupped within bright-red bracts which make for
a very vivid display over much of the year. The small yellow flowers together with surrounding red
bracts are a point in common with the poinsettia, which is also a euphorbia, though it is not closely related
and comes from Mexico. We have a large bush of E. milii in the East Shade House.
Euphorbia myrsinites
BED 8, etc.
Though the genus has many fascinating succulents, there are also many euphorbias which are not
succulent. One of these is E. myrsinites, with clumps of trailing stems clad in bluish leaves. It has
chartreuse flowers in spring. Many of its relatives also have green or chartreuse flowers. This plant
comes up readily from seed and is found at many locations in the garden, including bed 8.
Euphorbia resinifera
BED 7
This species from Morocco forms short dense clumps of four-sided plump stems. It is gray-green in
color, and has pairs of small but sharp spines. It flowers in late spring to summer, with bright yellow
flowers on the upper part of the stems. Though the flowers are not large, they are numerous and
attractive. We have a couple of clumps of this species on the east side of bed 7.
Euphorbia stellispina
BED 5
This species comes from the interior region of South Africa known as the Great Karoo. It typically forms
small groups of stout cylindrical stems with a “corn-cob” appearance, about 1 to 2 feet tall and up to 4
inches in diameter. Its unique feature is its branching spines, with the points radiating like little starbursts. There are some nice old specimens of this on the east side of bed 5.
Euphorbia stolonifera
BED 7
This is one of a large number of “pencil-stem” euphorbias. Native to western South Africa, it forms a
clump of slender gray-green cylindrical stems up to 2 feet or more long, initially upright but arching to
the side as they elongate. The small pointed leaves at the ends of actively growing stems do not persist
long, shedding to leave little scars which punctuate the stems. The flower color varies from yellow to a
brownish orange. There are 2 plants of this species near the southeast corner of bed 7, with differing
flower colors.