Crataegus rivularis |
Crataegus exilis |
|
---|---|---|
mountain river hawthorn, river hawthorn |
slender hawthorn |
|
Habit | Shrubs or trees, 30–50 dm. | Shrubs, 20–40 dm, branches ± weeping. |
Stems | twigs: new growth greenish, sparsely pubescent, early glabrescent, 1–2-years old often red-purple; bark on younger 2–5 cm thick branches dark gray-brown, sometimes copper-colored; thorns on twigs straight or ± recurved, 2-years old black or purple-black, glossy, fine, 1.5–4 cm. |
trunk bark dark gray or brownish, rough; upper twigs suberect, others ± spreading; twigs slightly flexuous, new growth pubescent, 1-year old light gray-brown, older gray-brown; thorns on twigs few, straight, dark, 1–1.5 cm. |
Leaves | petiole 1–2.5 cm, glabrous; blade elliptic to narrowly elliptic, 3–8 cm, length 2+ times width, thin, base cuneate, lobes 0 or small apiculi at ends of some vein tips, margins serrate, teeth numerous, usually acute, fine to coarse, venation semicamptodromous, veins 4 or 5 per side, larger often branched proximal to ends, apex acute, abaxial surface glabrous, adaxial appressed-strigose young. |
petiole length 25–30% blade, winged distally, pubescent young, glandularity not recorded; blade broadly obovate to broadly rhombic-elliptic, the smaller ± oblong-cuneate, 1.5–2.5(–3) cm, firm to subcoriaceous, base tapered, lobes 0, or 1(or 2) per side, subterminal, sinuses shallow (LII to 10%), lobe apex subacute, margins crenate-serrate (distal 1/2), veins 3 per side, apex subacute, surfaces pubescent young, particularly abaxially on veins, glabrescent; on extension shoots deeply incised. |
Inflorescences | 6–12-flowered; branches glandular-punctate; bracteoles early caducous, usually present, margins sessile-glandular. |
3–7-flowered; branches pilose-pubescent; bracteoles oblong-linear, margins glandular. |
Flowers | 14–17 mm diam.; sepals broadly deltate, 6–8 mm, margins entire, apex narrow, glabrous; stamens 10, anthers pink, sometimes ivory; styles 3–5. |
15 mm diam.; hypanthium pilose; sepals narrowly triangular, 3–4 mm, margins subentire or finely glandular-serrate, abaxial pubescence not recorded; anthers cream or ivory; styles 3–5. |
Pomes | deep red (mid Aug), black or blackish purple mature, suborbicular, 10 mm diam.; sepals ± erect to strongly outcurved or ± patent, 2–3 mm; pyrenes 3 or 4, sides eroded. |
red, orbicular, 5–7 mm diam., glabrous; sepals usually erose; pyrenes 3–5. |
Crataegus rivularis |
Crataegus exilis |
|
Phenology | Flowering mid May–early Jun; fruiting Aug–Sep. | Flowering Mar–Apr; fruiting Aug–Sep. |
Habitat | Intermontane streamsides, ditches, flood plains | Sandy soil, stream banks |
Elevation | 1300–2300 m (4300–7500 ft) | 60 m (200 ft) |
Distribution |
AZ; CO; ID; NM; NV; UT; WY
|
GA |
Discussion | Crataegus rivularis is most abundant in intermontane Colorado and Utah and is one of two hawthorns found in Arizona; it is rare in Nevada. There are reports from northwestern Texas (for example, D. S. Correll and M. C. Johnston 1970); they have not been verified. Crataegus rivularis is one of the more common woody species of mesic, valley bottom intermontane habitats. The species flowers early. Crataegus rivularis is superficially similar to the more or less sympatric, less common, C. saligna; it has larger leaves with fewer veins, larger flowers with ten stamens, and larger pomes. It differs from C. erythropoda little other than in leaf shape and ripe fruit color. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Crataegus exilis is only known from the type locality in south-central Georgia. Its appearance is distinctive; unfortunately, it is known only from flowering and fruiting syntypes. The species is somewhat anomalous in ser. Lacrimatae and slightly resembles a larger C. calva (ser. Apricae) but has pilose inflorescence branches, slightly different leaf shape, and somewhat different leaf margins. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 9, p. 510. | FNA vol. 9, p. 632. |
Parent taxa | Rosaceae > subfam. Amygdaloideae > tribe Maleae > Crataegus > sect. Douglasia > ser. Cerrones | Rosaceae > subfam. Amygdaloideae > tribe Maleae > Crataegus > sect. Coccineae > ser. Lacrimatae |
Sibling taxa | ||
Name authority | Nuttall: in J. Torrey and A. Gray, Fl. N. Amer. 1: 464. (1840) | Beadle: Biltmore Bot. Stud. 1: 76. (1902) |
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