J. Arnold Arbor. 1: 251. 1920.
Shrubs or trees, 30–50 dm. Stems: twigs: new growth rusty-tomentose, 1-year old chestnut-brown; thorns on twigs 2-years old dark gray to black, 1–3 (–5) cm. Leaves: petiole length 10–15% blade; blade elliptic to ovate, 2.5–4.5 cm, lobes 0 or sinuate (those on rapidly elongating shoots larger, usually proportionately wider than those on short-shoots, sinuately lobed), margins entire or barely serrate or crenate in distal 1/3 or 1/2, teeth gland-tipped, veins 3–5 per side, apex subacute to obtuse, abaxial surface densely rufous-tomentose, especially on veins, adaxial densely white or rufous-tomentose young, scabrous mature. Inflorescences 2–5-flowered umbels; branches glabrous or rufous-tomentose; bracteoles narrow, margins glandular. Flowers ± precocious, 15–27.5 mm diam.; hypanthium glabrous or rufous-tomentose; sepal margins entire or slightly glandular-serrate; petals 12 mm; anthers red; styles (4 or) 5. Pomes red, 10 mm diam.; sepals short-triangular; pyrenes 5.2n = 34, 51.
Phenology: Flowering Feb–Mar; fruiting May–Jun.
Habitat: Seasonally inundated depressions, ditches, sink holes, streamsides
Elevation: 10–100 m
Ala., Fla., Ga.
Crataegus ×rufula is restricted to the Florida panhandle and adjacent Georgia and southeastern Alabama.
Crataegus ×rufula is a presumed hybrid between the other two mayhaws or descendants thereof (J. B. Phipps 1988b) as shown by morphometric analyses. Although in some characteristics (for example, the usually sinuate leaf margin) C. ×rufula is like C. opaca, it lacks the characteristic elongate leaves of the latter. Crataegus ×rufula also tends to intergrade with C. aestivalis, with which it is fully sympatric. The frequency of C. aestivalis-like intermediates could well be accounted for by pure C. aestivalis being reasonably common through the C. ×rufula range and C. opaca being scarce there. Some, not all, individuals of C. ×rufula have relatively large flowers. Crataegus ×rufula is locally common and conveniently treated as a species.