Clethra

Illustrator: Barbara Alongi

Copyright: Flora of North America Association

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).

Selected References

None.

Lower Taxa

Clethra acuminata, Clethra alnifolia, Clethra tomentosa

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