Sedum of North America: Sedum smallii vs. Sedum pusillum

I've decided to start writing a few identification guides for those who might be interested in ID'ing Sedum.

Both Sedum smallii and pusillum are native to North America, almost only found from North Carolina to Alabama. Both species are known to grow together in the same areas, though it appears that S. pusillum may be rarer (But this may be the fact that many believe it is simply a slightly odd S. smallii).

Both species are tiny annuals, both have small usually-4-petal flowers, small juicy leaves, and grow in similar conditions. Below is a general guide on differentiating the two.

Sedum pusilllum:

• Glaucous. Sometimes it may be red, though new growth will be glaucous.
• Stems usually branch at the base.
• Leaves more elongated on scapes
• Fruits/seeds split open on upper surface.

• Seed pods more elongated, more like a "+" than a "✦"
  Young plants: https://www.inaturalist.org/observations/108340121
  Scapes: https://www.inaturalist.org/observations/73739000
  Flowers & Fruits/seeds: https://www.inaturalist.org/observations/110098644
  Very good picture of seeds: https://www.inaturalist.org/observations/164842838
  Occasionally, S. pusillum may create small basal rosettes... A rare find
  Basal rosettes: https://www.inaturalist.org/observations/70274972

Sedum smallii:

• Bright red, not glaucous. The point is, it should not be glaucous.
• Usually unbranched (at base)
• Leaves more rounded/bead-like on scapes
• Fruits/seeds split open on lower surface

• Seed pods more wide and less long, more like a "✦" than a "+"
  Young plants: https://www.inaturalist.org/observations/152971443
  Flowering plants: https://www.inaturalist.org/observations/154031630
  Flowers & Fruits/seeds: https://www.inaturalist.org/observations/158839243
  Very good picture of seeds: https://www.inaturalist.org/observations/164842644
  Occasionally, S. smalli may create small basal rosettes... An uncommon find
  Basal rosettes: https://www.inaturalist.org/observations/149453904
  Another pic: https://www.inaturalist.org/observations/149838419

Note that because both species are annuals, none of the plants should have woody/corky stems. For example, a look-alike to S. smallii, S. album (introduced), can get woody stems with age. In addition to this, S. smallii and S. pusillum generally will not grow in a connected stem-y network (other than branching in individual plants). So, if the colony is a mess of stem-y spaghetti, it is not likely to be either of these two species. Sedum album also has a slightly different leaf shape. Due to S. smallii and S. pusillum's life cycle as an annual, generally, stems and scapes will not trail around like the other perennial lookalikes.

Sedum album:
Picture of stems: https://www.inaturalist.org/observations/162088812
Growth pattern: https://www.inaturalist.org/observations/162015586
Flowers: https://www.inaturalist.org/observations/162268586
A particularly juicy clone that looks similar to S. smallii (Noticed the interconnected corky stems): https://www.inaturalist.org/observations/162294591

Another look-alike, Sedum dasyphyllum, can sometimes resemble S. pusillum. This is also an introduced species. Though, S. dasyphyllum has a different leaf-to-stem ratio, and the flowers are quite different.
Flowers: https://www.inaturalist.org/observations/161702877
Plant in bloom (Notice the leaves on the scapes!): https://www.inaturalist.org/observations/161930214
Large colony (Notice how they are interconnected): https://www.inaturalist.org/observations/161081198
Young plants: https://www.inaturalist.org/observations/161627799

Hope this helps,
Picklejar

Posted on 18 de maio de 2023, 03:04 PM by picklejar