A putative hybrid found in cultivation between S. monadelpha and S. pseudocamellia Koreana Group, although this never seems to have been confirmed. It resembles S. pseudocamellia but differs by having larger oblong bracteoles that are not adpressed to the sepals, and has smaller flowers – though they are larger than those of S. monadelpha. From the latter it differs in having sepals with rounded ciliate apices. S. × henryae only produces 2 seeds per locule, as in S. monadelpha, unlike the 4 of S. pseudocamellia. Bark characters are intermediate. (Spongberg 1974, Spongberg & Fordham 1975, Hsu et al. 2008).
USDA Hardiness Zone 5–7
RHS Hardiness Rating H5
Stewartia × henryae was first recognised at the Henry Foundation for Botanical Research, Gladwyne, Pennsylvania, prior to 1964, when it was named in honour of the founder, Mary Gibson Henry (1884–1967). It has since occurred in other collections where both parents are grown, notably at Polly Hill Arboretum and Arboretum Wespelaar. Hsu et al. (2008) note that it can have excellent autumn colour.
Most clones of S. × henryae fall short of equalling S. pseudocamellia but this selection from Polly Hill Arboretum is highly regarded for its fastigiate habit, free-flowering with abundant smallish flowers (3.5 cm diameter) and good red autumn colour (Hsu et al. 2008, PlantLust.com accessed July 16). It was a seedling from commercial seed sown in 1959, planted out in 1963 and first flowering in 1969. By 1991 it was 9–10 × 3–4 m, forming a narrowly vase-shaped tree on a richly coloured trunk (Polly Hill Arboretum). Although Hsu et al. (2008) state that is difficult to propagate it was available from several US nurseries in 2016, and it is cultivated at Arboretum Wespelaar.