Euphorbia horrida vs Euphorbia polygona

If you have a succulent plant and need help identifying it, this is the place to post it.
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Buck Hemenway
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Euphorbia horrida vs Euphorbia polygona

Post by Buck Hemenway »

So, here's how I see the difference between these two.

Euphorbia horrida. Longish stems (to 1 meter or so). The flower parts are yellow/green throughout with a slight purple cast.

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Euphorbia polygona. Some shorter stems, will clump much more densley than horrida. Notice the purple color of the flower parts except the actual flower itself

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Euphorbia poylgona v. snowflake. Flower parts are purple, the flower itself is yellow. This one is slightly more along in the flowering process.

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Euphorbia horrida v. minor. Short to no stem (globose) notice the flower parts colors the same as E. horrida even thought the cyanthia are slightly shorter.

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Buck Hemenway
Mike
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Post by Mike »

pretty plants and pics.

The Euphorbia Journal says polygona varies a lot, dark green to blue grey. They blend into horrida, generally poly is narrower and more green.

The Euphorbia.de site says

"All var. of E. horrida are quite variable in size and colour and therefore hard to distinguish.

E. horrida var. horrida is usually white. Depending on season and cultivation conditions the plants look quite different, however.

E. horrida var. major is dull green-gray and builds very thick stems with the age.

E. horrida var. striata differs in having stems which are bluish grey to silver, and the with the age very wavy angles which are marked with stripes.

E. horrida var. noorsveldensis is very similar to E. polygona. It has more narrow and dull bluish-grey stems.

E. horrida „var. minor“ isn’t a true variety but a nice form that flowers already when about 3 cm in height.

Very close related is the also very variable E. polygona. Depending on the certain habitat the plants are up to 1 m high, white, wavy ripped and heavy thorned to small, light green and almost thornless. There are transitional forms beween E. horrida and polygona occuring in habitat. Generally E. polygona is greener and has more narrow stems.

Also E. anoplia is very close related. One can hardly tell it apart from nearly thornless forms of E. horrida / polygona.

A revision of the Euphorbias will eventually reduce E. horrida, polygona und anoplia to subspecies or varieties of one single species, and the present varieties to forms. "


lastly here is a plant bein sold as horrida noorsveldensis by Altman's - appeared frequenstly at Home Depot. As I recall, it didn't exactly match the plant shown in the Euphorbia journal.
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cactuslee
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Post by cactuslee »

WOW, euphorbias are so cool, you can't find them in my neck of the woods. sure wish you could cause i would be a euporbiaholic if you could. cool pics.
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cruaux
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Post by cruaux »

Lee, if you want to lay your hands on nice Euphorbias, Aridlands Nursery in Tucson has a fair few.

No relation to them, other than being a happy customer. I've also gotten some from Miles-to-Go, but Miles' selection is not as extensive as Aridlands.
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lancer99
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Post by lancer99 »

Thank you, Buck, for opening that particular can of worms :)

From Gerhard Marx's article "The Succulent Euphorbias of the Southeastern Cape Province, Part Two" in the Euphorbia Journal vol. 9...(describing of E. polygona):

"...the only roughly reliable distinguishing characters between E. polygona and E. horrida are the narrower and more green stems of E. polygona. Florally, there are hardly any consistent differences -- most forms of E. horrida have purplish cyathial glands, identical to those of E. polygona."

The IHSP describes E. horrida v. major and v. noorsveldensis as having dark purple nectar glands, while those of E. horrida v. horrida are described as green (it doesn't say anything about v. minor).

The Euphorbia Journal published a pic of E. horrida v. horrida in the first volume, which they corrected in the second volume as being E. polygona.

E anoplia may be a hybrid, with one of its parents E. polygona.

E. inconstantia may be a hybrid of E. polygona and E. pentagona.

It seems to be a horrible mess, and given the promiscuous nature of the stipular-spined African species, not likely to be sorted out soon, from what I've read.

-R

PS Which variety of E. horrida is this?

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Buck Hemenway
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Post by Buck Hemenway »

It's pretty unfortunate that the lumpers are always winning. To my thinking there is a lot of difference in person between the plants that are generally thought of as polygona and horrida without regard to what conservative people, afraid to be wrong are writing. The blooms are very different and very consistant. In any case, we'll get ready for a lumping of the two. It may be, of course that dna studies will place them close enough to be lumped, but the morphological differences are pronounced as far as I am concerned.

This really reminds me of the argument stating that Aloe ferox and Aloe marlothii should be lumped.
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lancer99
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Post by lancer99 »

BTW, the first issue of Cactus & Co, free download http://www.cactuspro.com/biblio/en:cactus_co has an article on E. horrida and its variants, which mentions the overlap with E. polygona...."They are similar to an extent that whereas the distribution areas overlap it is almost impossible to identify the two species. As a consequence, you can be sure to grow a certain species only if you have locality data of your plants, and sometimes you can't either."

I bet that sounded smoother in Italian :)


-R
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Brontosaurus
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Re: Euphorbia horrida vs Euphorbia polygona

Post by Brontosaurus »

Can E. horrida and E. polygona be hybridized?
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