Euphorbia caput-medusae

Thanks to Jackie Chambers, UBC Botanical Garden horticulturist, for today’s photograph and write-up! Jackie writes:

Medusa’s head euphorbia is a low-growing, sprawling shrub that can reach up to 1m in diameter. It has thick, short, club-shaped branches which can range from 1-3 cm in diameter. There are no spines on this particular Euphorbia, however the stems have a bumpy texture; these are the remains of peduncles, or flower stalks from previous years. The stems are green and photosynthetic. Towards the top of the branches, the plant also produces some smaller, narrower leaves that are deciduous.

The branches arise from a caudex, or swollen stem, which has a primary function water storage. The caudex may be at ground level and visible, but may also be partly buried underground. Caudiciform is the term applied to plants that have caudices.

The inflorescence of the genus Euphorbia is unique in structure and has its own name: cyathium (pl.: cyathia). What appears to be one single flower is in fact a group of flowers, but condensed to simulate one flower. The staminate, or pollen-producing, flowers are tiny and just visible protruding from the lobes of the cyathia in the photos above, while the pistillate flowers extend above and beyond the lobes and staminate flowers. The Plant Heritage site has diagrams and more information on cyathia.

In Euphorbia caput-medusae, the cyathia are held at the tips of the branches, on short peduncles or stalks that are 1 cm long. The cyathia are cup-shaped (1-3cm wide) with 5 glands which are divided at the tips — producing the rather decorative whitish fringed edges. Glands secrete nectar that attracts pollinators. Medusa’s head has a long flowering season in South Africa and can bloom from May to September.

This species is found in sandy, stony slopes in Namaqualand and the southwestern Cape of South Africa. This particular specimen was photographed just outside of Clanwilliam, a small town about 250km north of Cape Town. The town is at the base of the Cederberg Mountains, which are home to many interesting plants.

Euphorbia caput-medusae
Euphorbia caput-medusae

9 responses to “Euphorbia caput-medusae”

  1. CHUNGII V

    Where can I get identification of these type of Euphorbia? I have two, one was actually labeled with this name but looks nothing like it? I actually posted them a while back on the forum to no response can someone help now?

  2. Alan Butler

    There is an International Euphorbia Society of which I am Chairman. We have many experts on euphorbias. Look at our web site http://www.euphorbia-international.org The expert on medusoid euphorbias is Rikus van Veldhuisen in Holland or contact me at alan-brook-side@hotmail.com

  3. SoapySophia

    So would the “Medusa” part of the name refer to the somewhat similar shape of a Jellyfish in Medusa form? I just got done studying phylum Cnidaria. The shapes aren’t all that similar, just a slight resemblance of the flower head in the first picture to the upside down new medusa jellyfish form in my book (genus Aurelia).
    Thanks!

  4. Quin

    This (or related medusoids) do well as house plants or under cover in Sonoma County, CA. Don’t think it will be happy outside in our cool wet mediterannean winter? I believe our winters are a little more harsh than South Africa’s……

  5. Eric Simpson

    I don’t know why this euphorb is called medusa, but that stage in jellyfish gets it’s name from the Medusa of Greek myth, who had snakes for hair, and the tentacles on the jelly are reminiscent of that. Perhaps the euphorb is so named because the stems look a bit like a bunch of writhing snakes.

  6. SoapySophia

    That’s why Medusa sounded familiar! Makes sense in both instances!

  7. Margaret-Rae Davis

    I have really enjoy seeing this Euphorbia. The Photopraphs are great and I learned so much from the write up.
    Thank you,
    Margaret-Rae

  8. Bob Burks

    Is it practical for this to be repotted and if so how and what for soil, etc.

  9. H.L. Todd

    I have been successful here in Palm Springs with summers over 45C with caput medusa. However, it eventually died. Is this like many euphorbias that need almost bone dry winters and regular light water in the summer?

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