Crataegus douglasii
 
Douglas Hawthorn

Thorns (C. douglasii and C. chrysocarpa)

Centre Block, Cypress Hills Interprovincial Park
19-June-2013

Note the thorn from C. douglasii is much shorter than the thorn from C. chrysocarpa.

Crataegus is a difficult genus, characterized by hybridization, polyploidy, and apomixis.  In many cases it is better to describe species complexes rather than individual species.  Nevertheless, I believe this specimen possesses enough characteristics associated with C. douglasii to ascribe it to this species.

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Douglasii: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 
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thorns stout and short; NOT [thorns long]

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leaves nearly glabrous beneath, more or less pubescent above; NOT [leaves pubescent beneath, at least on the veins]

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sepals short, triangular, acute but not attenuate; NOT [sepals attenuate, long-pointed] (BF)

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sepals ovate; NOT [sepals lanceolate, acuminate] (FOA)

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sepals hairy above

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sepals often without glands; NOT [sepals glandular-margined]

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fruit black or deep purple when ripe; NOT [fruit red or red-purple]

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nutlets pitted

 

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Crataegus Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 
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shrubs or trees; NOT [herbs, or with a woody base and otherwise herbaceous]

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plants taller; NOT [creeping dwarf shrubs]

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stems with stout thorns; NOT [stems not thorny]

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spines never leafy; NOT [spines leafy in the first year, leafless thereafter]

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leaves simple; NOT [leaves compound or lobed]

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leaves mostly incised-toothed or lobed; NOT [leaves entire to toothed]

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flowers usually more numerous; NOT [flowers solitary on a long peduncle]

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NOT [flowers in broad compound corymbs]

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ovary inferior; NOT [ovary or ovaries superior]

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ovary enclosed in and adnate to the hypanthium; NOT [hypanthium shaped like a saucer, cup or urn and free from the ovary]

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fruit a pome but often berry-like

 

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Rosaceae: Answers to key questions in Budd's Flora  leading to this family. 
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herbs; NOT [shrubs or trees]

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plants terrestrial or semiaquatic; NOT [plants aquatic, leaves submerged or floating]

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plants NOT with colored milky juice

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plants with more than one normal leaf

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some or all leaves alternate; NOT [leaves opposite, whorled, or basal]

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leaves with stipules; NOT [leaves without stipules, or having glands]

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flowers with two floral rings, and with each petal distinct from the others

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flowers regular in shape; NOT [flowers irregular in shape]

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calyx regular; NOT [calyx irregular, some sepals smaller than others]

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stamens usually separate or partly so, not in a column; NOT [stamens numerous, united into a column]

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ovary of one or more carpels, either separate or enclosed by a fleshy receptacle; NOT [ovary of 5 united carpels]