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Key to Tilia

Malvaceae

Tilia

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1 Leaf blades 8-25 cm long; flowers with staminodes; [collectively common and widespread natives].
  2 Lower leaf surfaces puberulent with bulbous glands, acicular trichomes, and (rarely) sparsely scattered stellate trichomes; fruiting peduncles and pedicels glabrous or sometimes puberulent; [generally northern, south to NC and TN]
  2 Lower leaf surfaces usually tomentose or becoming puberulent, with bulbous glands, acicular trichomes, and a predominance of stellate or fasciculate trichomes; fruiting peduncles and pedicels stellate-tomentulose (becoming puberulent in age); [collectively widespread in our area].
    3 Lower leaf surfaces grayish or brownish, loosely but densely tomentose with fasciculate and/or stipitate-stellate trichomes, either remaining tomentose or becoming puberulent, or puberulent from emergence and green beneath; lateral buds 3-5 mm long; pericarp 0.5-0.6 mm thick; [generally southern, Coastal Plain and Piedmont of NC, SC, GA and southward and westward]
    3 Lower leaf surfaces pale or whitish, densely stellate tomentose with appressed, sessile-stellate trichomes obscuring the surface (rarely becoming puberulent with age but with some stellate trichomes persisting along major veins, the margin, and/or the apex); lateral buds 5-8 mm long; pericarp 0.8-1.0 mm thick; [widespread in our area]
1 Leaf blades 3-9 (-12) cm long; flowers lacking staminodes; [rare exotics, sparingly naturalized in suburban woodlands].
      4 Leaves pubescent below; flowers 2-4 (-6) per cyme; fruit strongly ribbed
      4 Leaves glabrous below except for tufts of hairs in the vein axils; flowers 4-15 per cyme; fruit not or slightly ribbed.
        5 Cymes obliquely erect above the leaves; leaf blades mostly 3-6 cm long, the tertiary veins obscure as viewed from the upper side of the leaf
        5 Cymes pendent below the leaves; leaf blades mostly 6-9 cm long, the tertiary veins prominent as viewed from the upper side of the leaf