Before starting today’s entry, a note to local readers — there are still many apple varieties available for the second day of the Apple Festival tomorrow, including one of my favourites, the Salish apple.
Thank you again to Martin Deasy for guest-writing and photographing a series on the Hamamelidaceae. Martin, who trained at the Royal Botanic Gardens, Kew in its Kew Diploma in Horticulture program, concludes the series with this entry.
The bottlebrush-like inflorescences of Fothergilla major–unlike anything else in the Hamamelidaceae–are just one more example of the family’s remarkable diversity of floral morphology. As with Parrotiopsis, what look like flowers are in fact pseudanthia–compound inflorescences that “mimic” individual flowers. What appear to be petals are in fact clavate (club-like) stamens with inflated filaments, up to 32 in each flower; numerous reduced flowers are packed together on a rachis to form a single inflorescence.
An upland species native to the highlands of the southeast U.S.A. (the Appalachians of North Carolina and Tennessee), Fothergilla major occurs at altitudes of up to 1000m, particularly on dry ridges. It grows into a small deciduous tree, to ca. 5m, often suckering from underground stems to form dense thickets. The relatively late (for the family) anthesis in late April-May likely represents an adaptation to the harsher climate at altitude (the other Fothergilla species–the less hardy Fothergilla gardenii–is restricted to the coastal plain of the south-eastern U.S., and flowers in mid-April).
Absence of petals is an inherited trait (symplesiomorphy) of tribe Fothergilleae, whose members exhibit a progression from insect- to wind-pollination. The two insect-pollinated taxa, Fothergilla and Parrotiopsis, are also both the most basal; the more derived taxa (respectively Parrotia, Sycopsis, Distylium and Distyliopsis) have adopted wind as the principal means of pollination.
The comparison of Fothergilla and Parrotiopsis is revealing: the two genera are extremely closely related; yet each has recruited a different organ as attractant, lending their inflorescences radically different appearances. Nevertheless, the infructescences are very similar–indeed fruit morphology is astonishingly highly conserved across the entire Hamamelidoideae, a subject for a future post.