Trees & Shrubs 1: 117, plate 59. 1903.
Trees, 60–70 dm. Stems: trunks nearly black, 1 dm diam., bark deeply grooved; twigs: new growth nearly straight, dark-brown tinged with red, slender, slightly villous young, at end of 1st year bright redbrown, lustrous, marked by many small pale lenticels, 1-year old dark, dull reddish-brown; thorns on twigs absent or present, nearly straight, shiny, 1-year old bright chestnut-brown, slender, 3 cm. Leaves deciduous; stipules caducous, turning reddish, linear to linear-obovate, apex acuminate, glandular; petiole slender, 2–4 cm, slightly winged apically, white villous young, glabrescent, grooved; blade dark yellow-green, broadly ovate to suborbiculate, 5–6.5 × 4.5–6.5 cm, often wider than long, 1/2 grown when flowers open, thin but firm, base rounded, broadly cuneate, or truncate, lobes 4–6 per side, short, wide, lobe apex subacute to acute, margins coarsely serrate almost to base, teeth straight, gland-tipped, venation craspedodromous, veins 4–6 per side, prominent, slender, apex rounded, often short-pointed, abaxial surface paler, veins hairy, glabrescent except few hairs near base of thin yellow midvein, adaxial short-pale-hairy young, glabrescent. Inflorescences 5–10-flowered, compact; branches sparsely villous; bracteoles persistent until anthesis, oblong-obovate to linear, apex acuminate, margins glandular. Flowers 16 mm diam.; hypanthium hairy proximally; sepals slender, margins entire or minute, dark red stipitate-glandular, apex acuminate, abaxial surface glabrous, adaxial sparsely villous; stamens 20, anthers pale rose; styles 4 or 5. Pomes drooping on long, slender, glabrous pedicels, bright-yellow, suborbicular to short-ovate, 12–18 mm diam., lenticels numerous, small, pale; flesh yellow, thin, dry, mealy; sepals often deciduous from ripe fruit, small, with narrowly shallow cavity, slightly villous distally; pyrenes 4 or 5, acute at ends, rounded, 8 × 6 mm, dorsally very slightly grooved on back, sides plane.
Phenology: Flowering Apr; fruiting Sep–Oct.
Habitat: Brush, open woods, rocky pastures
Elevation: 100–200 m
Crataegus ×kelloggii was originally collected at the mouth of River des Peres, St. Louis, and was last found in Hannibal, near the Mississippi River; always rare, it is unknown in the wild today.
In all probability, Crataegus ×kelloggii is C. mollis × C. margarettae, as suggested by E. J. Palmer (1952).