Euphorbia Caput-Medusae Medusa-Head Euphorbia BED B

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 star- bursts. 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.