Clethra

Linnaeus

Sp. Pl. 1: 396. 1753

,

Gen. Pl. ed. 5. 188. 1754 ,

Common names: Sweet pepperbush
Etymology: Greek klethra, alder, alluding to resemblance of leaves of certain species
Treatment appears in FNA Volume 8. Treatment on page 364.
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Illustrator: Barbara Alongi
Plants sometimes spreading by root suckers. Leaves spirally arranged, often seemingly verticillate at ends of twigs; blade not coriaceous, margins revolute, surfaces glabrous or tomentose abaxially, glabrous or with sparse, short-stellate hairs, especially when young, adaxially, venation pinnate. Inflorescences borne on new growth, racemes solitary or in clusters of 2–4, bracteate. Pedicels ridged and somewhat flattened laterally, 1-bracteate basally. Flowers fragrant; sepals imbricate in bud; petals spreading at anthesis, weakly 5-ridged, apex obtuse; filaments adnate to corolla basally, straight or S-shaped, elongate, glabrous or hairy; anthers reflexed in bud, erect at anthesis, obsagittate, base attenuate, papillose, thecae divergent distally; style straight. Capsules globose, sutures thin. Seeds strongly flattened, slightly winged; testa thin. x = 8.

Distribution

s, e North America, Mexico, Central America, South America, e Asia, Atlantic Islands (Madeira).

Discussion

Species ca. 65 (3 in the flora).

References

None.

Key

1 Leaf blades: apex acuminate, margins toothed, proximalmost tooth averaging 2.4 cm distal to base; bracts longer than flowers; filaments glabrous or with scattered, simple hairs. Clethra acuminata
1 Leaf blades: apex obtuse to acute, margins toothed, proximalmost tooth averaging 3.4 cm distal to base; bracts shorter than flowers; filaments glabrous > 2
2 Young shoots and abaxial surface of new leaves sparsely hairy, adaxial surface glabrous; petioles 2.5-3.5(-6) cm; styles 6-7 mm, hairy in proximal 1/2, hairs simple, straight; filaments 0.2-0.3(-0.4) mm wide. Clethra alnifolia
2 Young shoots and abaxial surface of new leaves woolly-tomentose, adaxial surface sparsely hairy; petioles 0.5-1(-1.5) cm; styles 3.5-5 mm, hairy; filaments 0.4-0.5(-0.7) mm wide. Clethra tomentosa