Number 5 looks like Opuntia pentlandii.

I recently bought this unlabeled cactus at a local Garden Centre assuming it to be a Melocactus but not 100% sure. If it is a Melocactus does anyone know the species? I don't think it is M. matanzanus even though it looks similar. As you can see from the comparison photo it is larger than my own Mel...

"Thanks" 'elieestephane and 'Grimm', you hard work is much appreciated.

The thing I like about this site is that I am always learning something new. Following up on your reply, l did a bit more research and found the following information. Mammillaria elongata 'Pink Nymph' is a hybrid of M. elongata and M. microhelia so you may still get what you were hoping for. As you...

Number one looks like Mammillaria microhelia.

I agree, it's definitely not a Mammillaria but a Gymnocalycium baldianum and a nice specimen. The plant behind it is some sort of Mammillaria. Not sure which one though.

My first thoughts looking at the spines was that it is Mammillaria karwinskiana reinforced by the wispy hairs between the tubercles.
I'm not an expert though, but it does look similar to my own specimens of M. karwinskiana.

I am still a bit confused as to the ID of this cactus. You would expect Echinopsis aurea to have a yellow flower but as you can now see it has flowered red. I did some further research and found a reference to Echinopsis aurea var. dobeana which flowers red so it could be that. It has also been sugg...

Looks a lot like Gymnocalycium ragonesei to me. Flower colour can vary from white to pink.

I'd like to add my "Thanks" as well Dave for taking the trouble to write such an interesting and informative article. I've not been on the forum long but have found all the members very helpful and I have learned so much from you all. Hopefully I will be able to repay the help I have recei...

Don't be too disappointed that it's not a Discocactus. It looks like yours has a flower bud just forming on the righ-hand side so you can look forward to a lovey flower like mine.

Thanks Salazar. Do you not think yours could be the same?

I thought #1 might be Notocactus werneri. I bought the following cactus which was named N. submammulosus (which it clearly isn't) and thought it was N. werneri until it flowered. It had a yellow flower and N. werneri has a pink flower so I'm still not sure what mine is. IMG_1798.JPG IMG_1799.JPG May...

Looks like Rebutia violaciflora to me (see link) https://goo.gl/zrHX0S

This cactus only came into my possession a short time ago. I know it is a Mammillaria but not sure which one. H:23" W:3.5" Spines - Central/s:1 Radials:16-20 Flowers:12mm Bright Pink IMG_0718.JPG IMG_0709.JPG IMG_0712.JPG As you can see it has been held upright with 4 bamboo canes and 4 ba...