Sedum acre vs. Sedum sexangulare
Have been asked about differentiating two of the common yellow-flowering Sedum species in Europe.
If you compare the two:
S. acre has leaves that are broadest at the base, and somewhat triangular in outline.
S. sexangulare `s leaves are more or less the same width from base to tip (or broadest above the middle).
Also, consider the latin names: acre => pungent taste (not always though).
sexangulare => sometimes you can see the leaves sticking out of the stem into six directions only, so that from above you could place a hexagon over the tip of the leaves
