Some questions relating to Opuntia robusta

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Kaelkitty
Posts: 13
Joined: Fri Dec 14, 2007 10:56 pm
Location: Adelaide, Australia

Some questions relating to Opuntia robusta

Post by Kaelkitty »

Hi All,
I was going through all the Opuntia pictures today, trying to ID some plants for a friend and I came across something odd. First of all, the two pictures here: http://cactiguide.com/cactus/?genus=Opu ... urangensis" onclick="window.open(this.href);return false; are acknowledged as not being O. durangensis, and I am perfectly happy to see them left here for the reasons cited on the page. However, it would be nice if these pictures were ALSO posted on the Opuntia robusta page itself, especially since there are no pictures of the spiny form of O. robusta on its own page!

The second oddity concerns the first two pictures on this page: http://cactiguide.com/cactus/?genus=Opu ... martiniana" onclick="window.open(this.href);return false; - these also look awfully like O. robusta to me. Could this plant be checked out? I can't speak for the species O. martiniana itself as I've never grown it in person, but those top two photos certainly don't seem to match the rest of the shots on the page.

Finally, if it is not being too annoying, I'd appreciate it if someone who is good with Opuntias could have a look at the thread here: http://davesgarden.com/community/forums/t/1349503/" onclick="window.open(this.href);return false; and see what they think about my suggestions. I do find Opuntia species difficult to ID because it is illegal to grow them in the ground here and the plants I do have access to may not be typical in form, having been restricted to pots for their entire lives.

Ciao, KK.
peterb
Posts: 9516
Joined: Mon Aug 07, 2006 4:19 am
Location: Chandler, Arizona, USA

Re: Some questions relating to Opuntia robusta

Post by peterb »

Interesting observation regarding the plant labeled at Opuntia martiniana at the Desert Botanical Garden. I have seen it many times and haven't questioned the ID but I can get a look at the accession info for the plant and double check it. I agree, very different morphology from Marc Beckstrom's plants. The three Opuntia at Dave's Garden are engelmannii, unknown and stricta, in my opinion. Opuntia can be very difficult to ID indeed, especially from photos and with no habitat info.

peterb
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daiv
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Re: Some questions relating to Opuntia robusta

Post by daiv »

Good point about including those pictures on the robusta page. Easy to do! I think I expected to get O. durangensis pictures much sooner and figured I'd change it at the time. Didn't expect it to be so long. So at this point, I think it would be best to just switch it.

For the second, I can check and see if Marc gave me any info on these when he sent me his pictures. He has given me lots of feedback on existing images as well as new images. So 99% sure that he did not think those first two were out of place, but will double check. I am quite sure that they are not actually robusta, however.
All Cacti are succulents, but not all succulents are Cacti
A. Dean Stock
Posts: 458
Joined: Sat Oct 16, 2010 2:41 am
Location: 40 south 7440 east Kanab, Utah (Johnson Canyon)

Re: Some questions relating to Opuntia robusta

Post by A. Dean Stock »

The photos of O. martiniana at the DBG do not look typical to me. Opuntia martiniana can only be identified by locality, chromosome count and structure of the style. I've seen a number of O. phaeacantha hybrids in Arizona that look much like O. martiniana but are not. Opuntia martiniana is a tetraploid and has an odd shaped style. It is probably a clonal hybrid population and derived from parentage similar to that of O. x curvispina. A number of Opuntia taxonomists in the SW U.S. do not believe that O.martiniana should be regarded as a distinct species. The plants in the photos supplied by Marc Beckstrom are likely O. "martiniana" but they need to be chromosome counted and the style examined to make sure. Hybrids involving the O. phaeacantha and O. engelmannii complexes are difficult to deal with and especially so in Arizona.

Dean
Albert Dean Stock,Ph.D.
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