Crataegus sect. Douglasia
Arbor. Frutic. Brit. 2: 823. 1838.
Shrubs or trees, (20–) 30–100 (–140) dm. Stems: trunks 1–few, usually ± erect, bark plated, ± exfoliating; compound thorns on trunks sometimes present; thorns on twigs determinate, usually numerous, straight to ± recurved, slender to stout. Leaves: blade ± rhombic to ± elliptic, elliptic-oblong, or ovate-rhombic, sometimes ± obovate, oblanceolate, or suborbiculate, 3–8 cm, ± coriaceous to ± thin, lobes 0 or 1–4 per side, obscure to evident and sinuses shallow to deep, veins (3 or) 4–9 (–12) per side, absent to sinuses. Inflorescences: branches glabrous or pubescent; symmetric bracteoles present, basal stipuliform, falcate bracteoles absent. Flowers: post-mature petals pale paper brown; stamens 5 or 10–20, anthers white to ivory, pink, or purple, sometimes puce. Pomes bright or deep red to purple or black (late Aug), reddish purple to black (late Sep); pyrene sides usually pitted, sometimes plane.
w, nc North America
Species 16 (16 in the flora).
Section Douglasia comprises all the North American hawthorns (except Crataegus brachyacantha) with purple (burgundy in two) to black fully mature fruit, usually fairly short (1.5–3.5 cm) thorns, and laterally eroded pyrenes. The lateral erosion or pitting on the pyrenes is not always very deep or as conspicuous as in C. macracantha and close allies.
|1||Leaves: blades narrow, more than 2:1, lobes 0, veins 6–8(–12) per side; flowers 10–13 mm diam.; stamens 20, anthers cream; bark on younger 2–5 cm thick branches often shining coppery, horizontal lenticels present.||Crataegus ser. Cerrones|
|1||Leaves: blades usually broader, less than 1.6:1, lobes 0 or 1–4 per side, veins (3 or)4 or 5(–7) per side; flowers (10–)12–22 mm diam.; stamens 5 or 10(–20), anthers white to ivory, pink, or purple, sometimes puce; bark on younger 2–5 cm thick branches usually dark gray-brown or orange, conspicuous horizontal lenticels absent||> 2|
|2||Stamens 10, anthers pink or pink-purple to purple; flowers 14–18 mm diam.; thorns on twigs slender.||Crataegus ser. Cerrones|
|2||Stamens 10(–20), anthers pink or ivory to white, sometimes puce; flowers (10–)12–18(–22) mm diam.; thorns on twigs usually ± stout, sometimes slender||> 3|
|3||Thorns 2–5(–7) cm, slender to stout; inflorescence branches usually sparsely villous, sometimes glabrate; sepal margins denticulate to finely, sometimes strongly, glandular-serrate; pomes bright red to purple (late Aug), reddish purple to deep purple, often nearly black (late Sep), sepals conspicuous unless eroded, usually erect-patent, sometimes ± reflexed, usually accrescent (except in C. williamsii).||64c.Crataegus ser. Purpureofructus|
|3||Thorns 1–3.5 cm, ± stout; inflorescence branches glabrous or pubescent; sepal margins subentire, finely glandular distally; pomes black or dark purple mature, sepals short, reflexed or patent-recurved, not accrescent.||64c.Crataegus ser. Douglasianae|