Leaves 6–8 per plant, basifixed, alternate; petiole pale green, or pale to dark claret, reddish brown when dry, 5–20 cm long; leaf blade chartaceous, asymmetrical, broadly ovate, 4–13 × 4–14 cm, base cordate, apex acute, margin irregularly dentate, venation palmate, veins 7 or 8, adaxial surface densely pubescent, dull light green or vinaceous-greenish, glossy, abaxial surface densely hairy especially on veins, green or dark vinaceous.
Stipules
Petiole Angle of Attachment
Symmetry
Leaf Shape
Moreover, the leaf color in different populations in ChiangRai and Mae Hong Son Provinces varies from pale light green to dark vinaceous according to light, shading and soil composition. Differs from the allied Begonia delicatula in having caducous, not persistent, stipules, a denser indumentum over all vegetative parts. B. delicatula has glabrous stems, not densely hairy, and leaves with scattered, not dense hairs; The leaf lamina of Begonia delicatula is orbicular-reniform, whereas in B. phutthaii it is orbicular-ovate; the lamina margin of B. phutthaii is acutely dentate, whereas in B. delicatula it is shallowly and broadly crenately lobed and denticulate. The basal lobes of the lamina overlap in Begonia phutthaii, and do not overlap in B. delicatula.
