In Greek mythology Medusa was a beautiful sea nymph (one of the Gorgon Sisters) who had a ‘relationship' with Poesidon. Athena was pissed about it and turned her hair into snakes (and made her ugly, too, I gather). From then on all who looked upon her turned to stone. Thankfully that is not how the medusoid Euphorbias act, but they do have ‘snake-like' branches/limbs/arms that extend from a central caudex in a ‘medusoid fashion'. And they are not ugly, either.
a pastel painting I did of Medusa
These primarily southern African plants are fairly common in cultivation and some are so common one can find them at virtually any nursery selling a variety of succulents (large garden outlet centers often have one or two of these). These are technically caudiciform Euphorbias (see article on caudiciforms I wrote earlier this year) but they are often classified separately for showing purposes as there are hundreds of other caudiciform Euphorbias that do not have ‘arms'. Some of these Euphorbias have some, cylindrical, very-snake-like arms while others are only vaguely medusoid with spiny, angular limbs of various shapes and numbers. However most have arms that do not branch and all extend from the central caudex.
Euphorbia flanaganii at a nursery
But surprisingly these are some of the easier Euphorbias to grow, generally being moderately cold tolerant and far less prone to rot than many of the other caudiciform Euphorbias (this is a generalization and not a ‘rule'). Many of the medusoid Euphorbias reportedly have several periods of ‘down time' (I call it going into a coma) when overwatering is much more risky- much of the dead of winter, and the hottest time mid-summer. Still, I am one of the most careless waterers known to succulent cultivation and have yet to rot a single medusoid Euphorbia that I can think of (except for a few cristate forms). At times of extreme stress/ drought some of these plants can lose these arms only to regrow them when water/rain becomes available again. I have not seen this happen to my plants as I usually water too much rather than too little.
Euphorbia caput-medusae recovering from some tragedy in a botanical garden- this is about the only time I have seen a problem with one of these plants in cultivation
All these Euphorbias have the typical white, latex-like toxic sap that oozes whenever an arm is broken or injured. These medusoid Euphorbias as a group seem to among the less toxic or irritating of the Euphorbias, some even common fodder for range cattle in South Africa. Still, precautions should be made in case one is unusually sensitive to these saps, and certainly try not to get any of it the eyes or mouth as the experience will undoubtedly be quite unpleasant.
Below is a brief discussion of some of the plants I have grown, along with a number I have not, but seen in cultivation. I have not included Euphorbias that have arms that arise from is obviously the root stock, as there are dozens more (at least) that do this. True medusoid Euphorbias all have a central stem in addition to its roots.
Examples of medusoid-like Euphorbias that do not have true caudex stems: Euphorbia knuthii, Euphorbia micrantha and my Euphorbia hamata seedling
Euphorbia squarrosas and my own Euphorbia stellata, both excellent garden as well as potted plants here in southern California... but no true caudex on either of these
Euphorbia cylindrifolia and Euphorbia decaryi are sometimes included in the medusoid category as they do have succulent stems and long, snaky arms, but the stems in these two species are not usually considered truly caudicorm
Euphorbia caput-medusae: I discuss this first as this is the classic medusoid Euphorbia. It is a moderately large plant with a large, thick cylindrical caudex (stem) from which dozens, if not hundreds of long, thick, tubular arms extend in a radial pattern from the caudex. The length of the arms seems to depend partly on exposure to sun and water, as well as age. Plants grown in some sun or pots that are watered well will grow long arms, often twisted and extend several feet or more from the caudex. Plants grown in full sun and not watered much tend to be much more symmetrical and have shorter, more closely spaced arms that may extend only 12" or so. This is a pretty easy plant to grow in my experience and it does great in both pots and garden situations. I have not had this plant long enough to know how cold hardy it is, but it easily tolerates mild, short frosts, and seems to handle long periods of cold winter rains without trouble (I would not recommend watering this plant with tap water in cold weather, but for some reason rain seems to be fairly harmless). Flowers in summer are usually white, but I have seen yellow flowers in the plant files.
Nicely grown Euphorbia caput-medusaes in various botanical gardens
potted specimens (mine, one belonging to Kelli (thanks for the photo) with odd yellow flowers, and plants growing outside the Haunted House in Disneyland)
Huge specimen showing how this plant can get out of control and become somewhat unsightly (in a botanical garden); on the other hand, this is a nicely grown well controlled plant in Los Angeles in a private garden
Euphorbia arida is a smaller plant that I have been growing outdoors for just over a year now. I assumed it was just another Euphorbia that was soon to rot (as so many do in the winter here when it's cold and rainy) but it did great and is growing easily. It eventually forms a relatively tall caudex, up to 1' perhaps, and is covered with short, relatively thin arms. This one is from South Africa and not that common.
two shots of my little Euphorbia arida plant in the garden, and several nice mature plants in a show
Euphorbia crassipes is another South African plant that stays pretty small, with thick but short arms, making it a perfect plant for pots, or possibly small, open controlled xeriscapes. I have no personal experience with this one.
Euphorbia crassipes in a show, and private collection (second photo by senlarrs- thanks)
Euphorbia decepta is another short-armed South African medusoid somewhat similar in overall shape to Euphorbia arida (I sometimes have difficulty telling the two apart). I have not grown this species.
excellent example of Euphorbia decepta in show
Euphorbia esculenta is one of the most ornamental of the classic medusoid Euphorbias with smooth, thick, pale-green arching arms. I personally cannot tell this plant from Euphorbia inermis (a plant I have in my garden)- even the flowers look somewhat similar. I need to see two of them side by side. Anyway, this is both a excellent potted plant as well as a great landscaping plant, forming plants up to 2' or more diameter with dozens and dozens of arms of uniform diameter. This plant has a caudex that normally is mostly below ground, but in cultivation most raise it up for ornamental reasons.
garden and potted plant of Euphorbia esculenta
Flowering garden plant and close up of flowers
The most common by far of all the medusoid Euphorbias is Euphorbia flanaganii. I have seen it for sale in every home and garden center I have visited. It has even shown up in the garden in several spots as a weed, probably piggy-backing on another plant. It can be grown from an arm cutting fairly readily, though I have not done that on purpose. This plant has moderately thick caudex of 3"-4" and a myriad of soft, bendable, somewhat thin, deep-green arms that can grow up to about 1' long (though usually less). Euphorbia flanaganii is an aggressive grower and so far I have not found a situation in which it doesn't excel in my garden. Plants in full, hot sun have short arms of 2"-4" and tends to have a reddish to purply hue. Plants in more shade are a brighter green and have long, floppy arms. This plant flowers readily periodically throughout the year though usually not in the blazing heat of mid-summer, or the cold, wet dreariness of mid winter. It is easily cold hardy down to 24F as many of mine were exposed to this temperature last winter and did not show any signs of stress. It is drought tolerant, but newly transplanted specimens cannot survive too long without some water as I have discovered. However, I have yet been unable to overwater this plant and it seems amazing resistant to rot from this practice. This is a good starter species and does great in pots as well as in the garden. Cristate forms of this are common in cultivation and I have had several normal individuals in the garden spontaneously through a few cristate arms. These cristate forms are much more rot-prone, however (oops).
Cristate form, and garden plant throwing a cristate arm
Euphorbia gamkensis is another South African medusoid which I have personally not tried- it reportedly is only hardy to 10b but I am not convinced of that until I kill one myself. This is another classic medusoid with upright arms coming off a relatively thick caudex.
young and maturing Euphorbia gamkensis plants in shows (second photo thanks to Xenomorph)
Euphorbia gorgonis is a moderately common species that I have difficulty distinguishing from Euphorbia flanaganii. The overall shape, size, arm anatomy and flower color is nearly identical, though Euphorbia gorgonis seems to be a less aggressive grower with much shorter arms. I have several of these, including a variety known as brevirama (I assume that means short-armed, as the arms do tend to be relatively shorter). The normal form is a very cold tolerant plant, just as is Euphorbia flanaganii.
Euphorbia gorgonis in my collection (first and third photos) and in botanical garden (middle photo)
my own plant flowering showing leaf production in spring
Euphorbia gorgonis var brevirama
Euphorbia inermis, the species that looks like Euphorbia esculenta, has numerous thick, closely spaced arms and is, to me, the most ornamental of the group. The caudex in both these species can be up to 8" in diameter with many dozens of short arms arising from the sides (longer in some shade). As with E esculenta, it is both a great landscape plant as well as wonderful potted specimen. My Euphorbia inermis in the yard seems quite durable and quite resistant to rot, cold or sun damage, flowering routinely every summer.
Euphorbia inermis in private garden, in the ground in a nursery (old plant) and in a plant show
exceptionally large garden plant (thansk RWhiz) and flower detail on my own plant
Euphorbia pugniformis is another cold and heat tolerant medusoid plant from South Africa. This is reportedly one of the easiest of the bunch to grow from arm cuttings, though I have not grown this plant myself. In fact, I am at a loss to say exactly how this plant differs from several others.
Euphorbia pugniformis (second photo Xenomorf)
By the time you have gotten down the list to Euphorbia superans I have certainly lost most of my ability to tell some of these apart. I have no personal experience with this species though I have seen it grown outdoors in southern California successfully in zone 10a. It sure looks a lot like Euphorbia flanaganii to me.
Euphorbia superans in private garden
Euphorbia woodii is in the same category as Euphorbia superans (some consider them the same species though they come from different parts of South Africa)- not ones I have tried nor ones I can tell apart.
Euphorbia woodii (photo by bootandall)
The following are a few more medusoid Euphorbias that I have only seen once or twice and know nothing about.
Euphorbia albertensis Euphorbia namuskflutensis Euphorbia suppressa
Euphorbia tridenta as indoor plant, and outdoor plant
Euphorbia fasciculata is actually one I have grown- pretty cold sensitive, but I am trying it again; Euphorbia inornata in second photo