The best I can do is say that, TO ME, aeoniums have rounded leaf tips (with a small little point right at the tip) and flatter leaves. Echeverias have pointed leaf tips and plumper leaves. Hens and Chicks are Sempervivums, an Echeveria lookalike with pointed leaves that are flatter and more densely packed.

Nancy

As my boss used to tell me: "The only stupid question is the one not asked!"

A bit of info, though not all-inclusive... (have to start somewhere) some Echeveria have glaucous leaves...with a "bloom" on the leaves that can be rubbed off. Aeonium do not.

Most (but not all) Aeonium have tiny cilia on the leaf edges. Some Echeveria can be fuzzy/hairy, but most times (not all), the hair is over the entire leaves, not just edges.

There are many factors to consider: shape, thickness, color (whole leaf & edges), tips of leaf, etc.

Blooms are most helpful with an ID, but in absence of those, you go by basics. But, there are many differences. I just happen to remember what they look like...and check my references (books, online, etc.) if in doubt.

There are many Echeveria that are alike, as there are many Aeonium that are alike. Sometimes, you need to see the blooms to differentiate between species.

If nothing stands out to separate it clearly from another species, it would need blooms to help out there. =)

As Nancy explained, Sempervivums are called hen & chicks, but Echeverias have also been known to go by this name. Semps also have cilia (hairs-like) on their leaf edges.

All 3 of these are in the shape of a rosette. All 3 of these genus can have offsets, but not all species do.

There are more whole leaf color variations within Echeveria, than the other 2.

Hope this helps...a bit. Think I'd better stop. I'm confusing myself! :P

To me, the primary differences are 1) country of origin (Aeoniums come from the Atlantic ocean islands in general) while Echeverias are mostly Mexican in origin 2) Aeoniums are monocarpic (die after flowering and 95% of Echeverias are not (but some are); With a few exceptions, Aeonium flowers consist of many yellow, daisy-like affairs, with the entire bloom sometimes dwarfing the original plant in size and shape while most Echeverias flower in simpler, usually arching peduncles lined with less showy, bell-shaped flowers, often of red or orange (some yellow); 3) Echeverias tend to be stemless to short-stemmed plants with thick, very succulent leaves, sometimes completely covered in a layer of fuzz, but usually smooth and rarely shiny... Aeonium leaves are thinner (but not always), usually sort of spoon-shaped and rosettes contain far more leaves in general than those of most Echeverias... ; 4) most Aeoniums are stalked plants with thick, succulents stems (though there are a number of Echeverias with stalked stems)... both plants are members of the same family so of course there will be many similarities as well...

Below are Aeoniums flowering (no Echeveria has flowers even approaching this appearance)

But then there are a few Aeoniums, such as A nobile that are very Echeveria-like (though more massive than any Echeverias I have seen). Below is my A nobile about 24" across.