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Key of some species

This is a note I made in summer of 2013. Post here as archive.


Branches appearing flattened, the leaves strongly appressed to stems primarily in one plane or at least squarrish in cross section.

  • Diphasiastrum tristachyum Branches appearing somewhat squarrish, rather than broadly flattened; often conspicuously blue-green in color; all leaves about the same size; ultimate branches 1-2.2 mm wide.

  • Branches strongly flattened; green; leaves on the flat underside of branches shorter than the other leaves; ultimate branches 1.8-4 mm wide.

    • Diphasiastrum complanatum: Branches with conspicuous constrictions (narrowings); lacking sterile tips on the strobili.

    • Diphasiastrum digitatum: Branches without conspicuous constrictions; sterile tips present on many strobili.

White oak group

  • Quercus alba: Glabrous at underside of leaves.

  • Quercus macrocarpa: underside of leaves has pubescence, only one stellera type hairs.

  • Quercus bicolor: underside tomentosa, two types of hairs.

Red oak group

  • Quercus rubra: the deepest sinuses extending 45-70% of the distance to the midvein; the petioles and green branchlets sparsely hairy or glabrous when the leaves are just expanding. Acorns.

  • The petioles and green branchlets densely hairy when the leaves are just expanding. the deepest sinuses extending 65-90% of the distance to the midvein.

    • Quercus velutina: Lower surface of leaves more or less pubescent; buds hoary-tomentose; cup scales of acorn silky-pubescent, spreading and squarish at the tip; lower dead branches not persistent.

    • Quercus ellipsoidalis: Lower surface of leaves glabrous or nearly so; buds glabrous, lustrous, only slightly angled in cross section; stubs of dead branches persistent on lower trunk.

Poison ivy

  • Toxicodendron radicans: Tall branching shrub often > 2m tall, or vine climbing with aerial roots; perioles moderately to densely hairy; leaflets ovate, usually more than 1.5 times as long as wide.

  • Toxicodendron rydbergii: Low shrubs with few if any branches and usually < 1m tall, not producing aerial roots; petioles glabrous or sparsely hairy; leaflet broadly ovate, usually less than 1.5 times as long as wide.

Osmunda cinnamomea

  • Only Cinnamon fern has the pale tan tufts of wool at the base of the pinnae.