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Prunus
See list of 19 species in this genus-
1a. Flowers and fruits sessile or subsessile; ovary and drupe densely pubescent; winter branchlets with 3 axillary buds at each node, the lateral ones inflorescence buds, the central one a leaf bud
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1b. Flowers and fruits borne on evident pedicels; ovary and drupe glabrous; winter branchlets with a single bud at each node
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2a. Drupes grooved, often glaucous; endocarp compressed and ± 2-edged; inflorescence in a fascicle that lacks leafy bracts at the base [Fig. 852]; sepals pubescent on the adaxial surface (at least near the base; glabrous in P. domestica);
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3a. Sepals with marginal glands; leaf teeth with a gland (note: the gland sometimes deciduous at maturity of the leaf and its former presence can be detected by observing a small gland scar on the tooth) [Fig. 854]
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4a. Flowers solitary or paired (rarely in trios) [Fig. 852]; drupes dark blue to black (red, yellow, or black in P. cerasifera); leaves convolute in bud; branches sometimes tipped by a spine-like process
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5a. Young branchlets and bracts densely pubescent; pedicels pubescent
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6a. Leaf blades 2–4 ×0.8–1.8 cm; drupes 10–15 mm in diameter; endocarp rugose
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6b. Leaf blades 3.5–6 (–8) ×2–4 cm; drupes (10–) 15–25 mm in diameter; endocarp nearly smooth
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5b. Young branchlets and bracts glabrous to sparsely pubescent; pedicels glabrous or sparsely pubescent [Fig. 852]
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7a. Hypanthium pubescent; leaf blades pubescent on the abaxial surface; petioles 10–20 mm long; flowers 10–20 mm in diameter; drupes 40–75 mm in diameter; branches usually lacking thorns
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7b. Hypanthium glabrous; leaf blades glabrous on the abaxial surface or sparsely pubescent along the midvein; petioles 6–12 mm long; flowers 20–25 mm in diameter; drupes 20–30 mm in diameter; branches sometimes with thorns
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4b. Flowers in fascicles of 3–5; drupes red to yellow; leaves conduplicate in bud; branches not tipped by a spine-like process
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8a. Petals 8–13 mm long, usually white changing to pink; sepals and pedicels tinged with or completely red; leaf blades coarsely and sometimes doubly serrate
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8b. Petals 5–7 mm long, usually remaining white; sepals and pedicels ± green; leaf blades finely crenulate-serrulate
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3b. Sepals lacking marginal glands (though they may be toothed); leaf teeth without a gland (though sometimes with a callous point) [Fig. 853]
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9a. Petals 7–12 mm long; drupes red to yellow, (15–) 20–30 mm in diameter; leaf blades abruptly acuminate at the apex
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9b. Petals 3–8 mm long; drupes blue-purple to purple-black (rarely yellow), 10–15 (–25) mm in diameter; leaf blades truncate to acute or gradually acuminate at the apex
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10a. Leaf blades ovate to elliptic or obovate (suborbicular in var. gravesii), truncate to acute at the apex, pubescent on the abaxial surface; pedicels pubescent; drupes (10–) 13–15 (–25) mm in diameter
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10b. Leaf blades lanceolate to oblong-ovate or narrow-obovate, acute to acuminate at the apex, glabrate to sparsely pubescent on the abaxial surface; pedicels glabrous (rarely pubescent); drupes 10–12 mm in diameter
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2b. Drupes not grooved, not glaucous; endocarp globose to subglobose (ellipsoid in P. susquehanae); inflorescence a raceme or a fascicle with leafy bracts at the base from the same winter bud (lacking leafy bracts in P. pumila, P . pensylvanica, and P. susquehanae) [Fig. 851]; sepals glabrous on the adaxial surface; terminal winter buds present
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11a. Inflorescence a raceme with 18–64 (–90) flowers, the pedicels shorter than the axis of the inflorescence [Fig. 856]
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12a. Leaf blades with more than 15 pairs of lateral veins (some of the veins inconspicuous), lanceolate-elliptic to ovate-elliptic, toothed with blunt, callous-tipped teeth, usually pubescent along the abaxial midrib with patches of white, turning red-brown, hairs; sepals oblong to triangular, entire or sparsely glandular-erose, persistent in fruit
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12b. Leaf blades with mostly 8–11 pairs of lateral veins, oblong to obovate, toothed with sharply pointed teeth, glabrous on the abaxial surface or with some obscure patches of hairs in the axils of the primary veins; sepals broad-triangular to semi-circular, conspicuously glandular-serrate, deciduous post anthesis
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11b. Inflorescence a fascicle with 2–10 flowers, the pedicels much longer than the axis of the inflorescence (if an axis is present)
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13a. Leaf blades with teeth that lack a gland [Fig. 853]; low shrubs 0.2–1 (–2.5) m tall
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14b. Branchlets minutely pubescent; leaf blades oblong to oblong-obovate, 15–30 mm wide, 2–3 times as long as wide, glaucous on the abaxial surface; plants ascending to erect, commonly 3–10 dm tall; endocarp ellipsoid, 5–6 mm wide
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13b. Leaf blades with teeth that possess a gland (note: the gland sometimes deciduous at maturity of the leaf and its former presence can be detected by observing a small gland scar on the tooth) [Fig. 854]; tall shrubs to trees, 3–20 m tall
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15a. Leaf blades broad-ovate to suborbicular, broadly rounded to subcordate at the base; young branchlets glandular-puberulent; inflorescence a 4- to 10-flowered raceme with a short axis, the axis present during flowering
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15b. Leaf blades lanceolate or elliptic or elliptic-ovate or elliptic-obovate, cuneate to narrowly rounded at the base; branchlets glabrous or pubescent, but lacking glandular hairs; inflorescence a 2- to 5-flowered fascicle without an axis or sometimes with a very short axis in fruit [Fig. 851]
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16a. Petals 4–7 mm long; flowers 12–16 mm in diameter; drupes 5–7 mm in diameter
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16b. Petals 10–15 mm long; flowers 25–40 mm in diameter; drupes (8–) 15–25 mm in diameter
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17a. Petals emarginate at the apex; sepals ascending to spreading; bracts of inflorescence brown to green-brown, usually deciduous; drupe 8–10 mm in diameter, purple-black
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17b. Petals entire at the apex [Fig. 851]; sepals recurved or reflexed (at least post anthesis); bracts of inflorescence green, persistent; drupe 15–25 mm in diameter, red to purple-black (rarely yellow)
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18a. Sepals margins glandular-serrate; petiole 10–20 (–25) mm long; proximal margin of leaf teeth much longer than the distal margin, therefore, the gland close to the sinus; leaf blades glabrous or essentially so on the abaxial surface (pubescent in early season)
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18b. Sepals margins entire; petiole 20–70 mm long; proximal margin of leaf teeth only slightly longer than distal margin, therefore, the gland well removed from the sinus; leaf blades persistently (though sometimes sparsely) pubescent on the abaxial surface
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Each photo represents one species in this genus.