IMO this is the best book about Astrophytum hybrids
https://www.uhlig-kakteen.de/en/roman-p ... =200051133
It is hard to find in US, but possible

E,villosa seems right, I think second also fits your suggestion - E.Eriosyce taltalensis subs. paucicostata f. viridis. The 3rd one gives me a vibe of one of the E.curvispina group (var.robusta may be?), but not sure.

anttisepp wrote: ↑Fri May 03, 2024 8:41 pm Karwinskiana has mostly white spines and white hairs in axils.

Agree about white spines in mature specimens and also in karwinskiana ssp.nejapensis. Spines on younger ones usually have brownish tips. white hairs also better develop in older karwinskiana plants imho.

For the first one I could suggest M.karwinskiana, for the second - check M.rhodantha, M.pringlei or nivosa. When it blooms the flowers will help to narrow down the species.

Agree, Notocactus (Parodia) buiningii

according to Britton & Rose (First published in Cact. 2: 125 (1920) Acanthocereus subinermis is a synonym of Acanthocereus tetragonus

Mammillaria bocasana would be my guess

Another one to consider, Thank you 7george!

Thank you for your suggestion, Tom! it was indeed bought from a retail nursery, no tag. Alensis is a possibility, I am considering gaumeri as well. Guess I need to wait some more and see how it grows and possibly blooms..

Thank you Anttisepp! it does remind of pachycladus, but at that age it should be already blue/bluish. Mine is as green as a cucumber.. Will keep growing it and observing if anything changes. I like the plant, name or no name

Hi, I have a columnar cactus that I cannot identify for some time. Guessing it might be one of the Pilosocereus species. Any help will be appreciated.

Looks like Mammillaria nivosa to me
https://llifle.com/Encyclopedia/CACTI/F ... ria_nivosa

Agree with anttisepp about M.haageana. Both perbella and formosa at that age are globose with flattened apex. Your plant is elongated, which is more often with young haageana (yours could be M.haageana ssp.elegans). Flowers could help to narrow it down.

You are right, it is difficult to say at that age. P. pachycladus is possible, but I would also consider P. languinosus or P. glaucochrous.
you can check photos on https://succulentalley.com/pilosocereus/

Could be Mammillaria pringlei