Philadelphus tomentosus is a shrub to 3 m tall, colonial from root sprouts, older bark grooved, shreddy, pale, brown, branching opposite, stems arching, rather weak, brittle, young twigs brown.
Leaves opposite with underside densely soft-hairy, sometimes slightly hairy above; egg-shaped, 4-8 cm long, margin slightly toothed.
Flowers fragrant, white, 3 cm diam. in 5-7 flowered unbranched clusters; regular, petals 4, stamens yellow, numerous, calyx lobes 4, from an enlarged base (hypanthium) in branched clusters of 5-7 in racemes (unbranched clusters), June-July.
Fruit: Dry capsules, seeds numerous.
Wetland status: NL.
Frequency in NYC: Very infrequent.
Habitat: Possibly escaped from cultivation or, more likely, overgrown horticultural specimens (DeCandido 2001).