Hermit:

I am in the process of attempting to root one myself. I put in in place about five weeks ago. It is resting on top of the soil straight up with sticks to hold it in place. I haven't tried to check if roots have started, yet, but it isn't rotting.... I have a variegated one, too.
Good luck to you trying to root yours.
Boyd

I've been watching the growth habit on mine (also a variegated)... and now I'm thinking that the standard of taking a cutting, letting it callous/dry, and then potting up the cut-end, may not be "the" route for this one. From what I THINK I have seen, it appears that before a new actual "arm" comes into being, there is first a spike - like a thin thorn - and then the "arm" develops. So now I'm thinking that maybe propagation for this type might be better achieved if a cut arm isn't set cut-end down into a rooting medium, but perhaps laid on its side... maybe those "spikes" would evolve into roots instead of how I normally expect roots to develop from a cut-end.

Make sense?

Have you seen the same type of "spikes" develop into "arms" on yours BoydsAGardener?

I LOVE this variegated plant though... I haven't seen a non-variegated version of the species yet but will be on the look-out, that's for sure. If I can pin down how to propagate this variety, it would make life easier for sharing!

I haven't seen any spikes yet, but I'll keep looking. I'll probably try the "laid-down version" for propogation if what I'm doing now doesn't work.
My apologies for mis-information in the last posting. I have a variegated one (the topic of your posting) and a green one. (I forgot the name). OOPS!
Good luck!

I would think that your non-variegated one would have the same name, just minus the "variegata" at the end most likely. I still haven't found any species-specific information on the net/web for rooting this one, but after reading a page (that I will paste below along with the url to it, since it has photos), I'm going to take a good look at my plant and see if I feel safe to take 3 or more cuttings from it to try rooting in different ways. The article does cite some specific species, but unless I overlooked it, mammilaris isn't one of them. You might find this info of use though - I know it does talk a bit about Medusa's Head - and I've got cuttings rooted of that one, so this additional info was nice to tuck away in my memory banks (and of course will get saved into a text file as well :)

copied info from:
http://www.euphorbia-international.org/Cultivation/propagation.htm
Vegetative Propagation

Propagation of euphorbias from cuttings is the easiest and quickest method for many species, and is also a way to prune an old plant back into shape. Cuttings should be taken with a sharp clean knife, if possible laying the plant down on a clean and smooth surface and using a pulling, rather than pressing motion to obtain a clean and clear cut. Branching species should be cut if possible at the branching point. Solitary plants such as E. bupleurifolia or E. piscidermis can be decapitated to encourage production of side shoots which can later be removed and rooted.

The best time to take cuttings is in the spring when growth starts, but summer is also suitable. Cuttings taken in autumn or winter have little time to root, and so cuttings should only be taken as an emergency to rescue plants suffering from root rot.

The latex appearing after cutting must be completely washed away in a glass of water or by spraying. Cold water stems the flow quickly as does brief exposure to a candle flame or match.

Euphorbias with large leaves should have leaves just above the cut removed with a knife. The cut surface should be left to dry before planting, one or better several days for leafless species. Leafy Madagascan species need only dry a short time. Dusting the cut surface with a hormone rooting powder will help roots form. For euphorbias we recommend 0.1% naphthyl acetic acid and not indolyl acetic acid which is usually found in shops. The planting medium can be the same as for seed sowing with the addition of some sterilised drainage material.

Rooting can take longer than expected but is accelerated by raising the soil temperature to around 25 C using a thermostatically controlled warming mat. Direct sun should be avoided.

If unrooted cuttings dehydrate, they can sometimes be saved by soaking in water at room temperature until then swell up again and can be replanted.

Rooting cuttings

Euphorbia greenwayi var. greenwayi Euphorbia myrioclada Euphorbia similiramea

A fast rooting method, which does not suit all species, is to stand cuttings in a narrow glass and fill up to 2-3 cm with water. Rooting can occur in 10-14 days.

Some euphorbias that can be rooted from side shoots continue to grow as branches and do not form the typical plant form. The medusa-head species are in this group as well as E. brevitorta, E. groenewaldii, E. tortirama and others. For these the so-called two-step cutting method is required. First a cutting is taken in the normal way. When this has rooted, a second cut is made just above the point where roots have formed and the cut is treated in the normal way. The tip can be re-rooted and when large enough can be cut again. The rooted stump will normally produce a plant of form typical to the species and this can then be removed when large enough from the mother cutting.

Some Madagascan euphorbias (E. francoisii, E. cylindrifolia, E. pachypodioides, E. ankarensis, E. millotii) have been successfully propagated from leaf cuttings. Leaves are gently pulled from the plants (not cut) and put into cubes of rock wool which are then placed on coarse sand in a tray. The surface of the sand should be covered with water (putting the leaves directly into damp sand also works, although with greater losses). Hormone rooting powder and fungicide assist the process. Both gentle heat or a cool position with a plastic cover to increase humidity, should produce the desired result. After 40 days the plants are sufficiently well developed to be potted.

Leaves of E. decaryi, E. primulifolia, E. moratii, E. cremersii and E. decidua will produce roots but do not develop plants. They remain as rooted leaves.

Finally a few words on the toxicity of the latex. Even small amounts can cause painful skin irritation. If you get it on the skin, it should immediately be washed off thoroughly under running water. On no account let the latex come into contact with the eyes or mucous membranes.

Thansk for the great info, Hermit!

What is the minimum size that a cutting/arm should be before trying to propogate? Many thanks!

Shannon, IME the larger the cutting / arm / pup the better its chances of rooting, all other factors being good. I've not rooted this plant but many others, and it's proven true too many times for it to be just mere luck. The preceding commentary is an excellent primer on how to do it - I don't know if it was mentioned, but bottom heat (not difficult this time of year if you take advantage of concrete / stone heated by the sun) is quite useful when rooting.

As to cutting size, I agree with cactusmcharris, who gave me some excellent advice when I was new at raising succulents. Considering the length of time it takes E. mammillaris to make roots, it stands to reason that larger may be better, as it would have more resources to sustain it. I think I usually chose a piece of around 4" or longer.

My present two plants of that species have tended to grow long arms and become top-heavy so that they need to be propped up, and more than one "arm" has too easily broken off, making me think that just laying it on the medium / soil to root might also get good results. Perhaps that is how it propagates in the wild.

Biwa, aka Biwako (For some forgotten reason, I had to re-register here, hence the name change.)

@hermitonthehill I know this is a very old convo but I’m looking for this info and came across this. Did you have any luck? Stick them in potting mix vertically or lay them down horizontally?

I have these and it was a sml pot grom HomeDrpot the center stem died so i pulled off the bumpy balls & just sat on succulent mix. will they just root like cactus?