I bought a small cactus from the garden center, but it doesn't say which species it is. Can anyone identify this cactus? For reference I put it next to a coin of about 3 cm (1.2 inch) in diameter. Thanks in advance.
It's almost certainly a species of Ferocactus. Unlabeled garden center plants usually are more or less common species... though not always! Ferocactus haematacanthus is a very rare species... there is another species with almost the same name-- F. hamatacanthus (missing the "e") is much more common. (The name with the "e", haematacanthus, means "blood(red) spines"; without, ie. hamatacanthus, means "clawlike or hooked spines".) But then, juvenile species of the genus often look very much one like another. I wonder if it is F. macrodiscus-- I've seen young plants of this species that look almost exactly like yours... but there are probably a half-dozen or more others that also do. Blooms might decide it, but apart from F. fordii, Ferocactus plants usually won't bloom until they grow very large indeed. After some 4-6 years the adult spination will also aid in identification. In any case-- it's a really nice plant!
Regards, John in Florida