Elkwater hawthorn

Shrubs, ˂densely branched˃, 20–40 dm. Stems: twigs: new growth ˂anthocyanin-rich˃, nearly glabrous, 1-year old medium to darker brown, older gray to dark gray; ˂bark on 2–5 cm thick branches gray-brown˃; thorns on twigs usually recurved, ± stout, 3–6.5 cm, 2-years old dark red-brown. Leaves ˂deciduous˃; petiole length 30–40% blade, hairy (only in adaxial sulcus), sessile-glandular; blade ovate or trullate-ovate to broadly elliptic, 3–3.5 cm at anthesis, 4–7 cm mature, ± coriaceous, base cuneate to broadly cuneate, lobes (2 or)3 or 4 per side, pronounced, ˂max LII 15–25%˃, lobe apex acute, margins serrate, ˂teeth numerous, small, acute to subacute˃, veins (3 or)4 or 5 per side, ˂distinctly impressed adaxially˃, apex acute, ˂shiny˃, abaxial surface glabrous, veins sometimes densely finely hairy along sides, adaxial ± densely appressed-scabrous hairy. Inflorescences 5–12-flowered; branches ± sparsely to moderately or densely pubescent; bracteoles ˂light brown˃, margins glandular. Flowers 15–18 mm diam.; hypanthium glabrate or sparsely to moderately pubescent; sepals ˂pale with some anthocyanin or light brown˃, triangular, 2.5 mm, margins denticulate to glandular-serrate, abaxially glabrous; stamens 10, anthers pale pink or pink; styles 3 or 4. ˂Fruiting pedicels glabrate or sparsely to moderately or densely hairy˃. Pomes reddish plum early (late Aug), dull purple mature (mid Sep), ellipsoid to broadly ellipsoid or ovoid, 10–12 mm diam., glabrate or moderately to densely pubescent; sepals usually erect-recurved, wide, 2.5–4 mm; pyrenes 3 or 4(or 5), sides ± eroded, often shallowly.

Flowering late May–early Jun; fruiting Aug–Sep. Thickets, light shade of Populus spp.; 800–1200 m; Alta., Sask.

Crataegus aquacervensis is widely distributed in the northern part of the Cypress Hills westward from the Adams Creek area and Fort Walsh. The species is superficially similar to the sympatric C. rivuloadamensis (ser. Montaninsulae) and C. chrysocarpa (ser. Rotundifoliae), differing from both by the more or less eroded lateral faces of the pyrenes and from the latter by the larger, more venous leaves, prominent fruiting calyx, and ripe fruit color.