Amelanchier nantucketensis

E. P. Bicknell

Bull. Torrey Bot. Club 38: 453. 1911.

Common names: Nantucket shadbush
EndemicIllustrated
Synonyms: Amelanchier oblongifolia var. micropetala B. L. Robinson
Treatment appears in FNA Volume 9. Treatment on page 657. Mentioned on page 649, 656, 661.

Shrubs, 0.3–2.5 m. Stems 1–70, rhizomatous, suckering and forming colonies. Leaves less than half-unfolded; petiole (6–) 9–15 (–22) mm; blade elliptic to oblanceolate or oblongelliptic, (11–) 29–41 (–55) × (13–) 19–29 (–42) mm, base rounded to cuneate, each margin with 0–4 (–10) teeth on proximal 1/2 and (0–) 3–8 (–12) teeth in distalmost cm, largest teeth less than 1 mm, apex subacute to rounded and mucronate, abaxial surface densely (moderately) hairy by flowering, surfaces sparsely hairy (or glabrous) later. Inflorescences (4–) 6–8 (–11) -flowered, (12–) 24–36 (–53) mm. Pedicels: (0 or) 1 (or 2) subtended by a leaf, proximalmost (4–) 7–14 (–38) mm. Flowers: sepals irregularly spreading or recurved after flowering, (1.3–) 2–3 (–3.9) mm; petals spatulate to oblong, (2.2–) 3–4.5 (–6.8) × (0.6–) 1–2 (–3) mm, sometimes bearing 1 or 2 tiny pollen-sacs near margins on adaxial surfaces; stamens (12–) 18–20; styles (4 or) 5, (1.7–) 2.6–3.7 (–4.3) mm; ovary apex glabrous or sparsely to densely hairy. Pomes dark purple-blue, 7.5–10 mm diam. 2n = 4x.


Phenology: Flowering Mar–May; fruiting Jun–Jul.
Habitat: Fields, sand-plain grasslands, heaths, glacial outwash plains, forest openings, disturbed sites, stream shores, among rocks or sand, dry habitats, ditches, swales
Elevation: 0–400 m

Distribution

V9 1129-distribution-map.jpg

N.S., Conn., Maine, Md., Mass., N.H., N.J., N.Y., R.I., S.C., Va.

Discussion

In the absence of flowering material, identification of Amelanchier nantucketensis is tentative; it is easily confused with A. spicata. K. M. Wiegand (1912) thought that A. nantucketensis originated as a hybrid between A. spicata (which he called A. stolonifera) and A. canadensis (as A. oblongifolia).

Amelanchier nantucketensis can reach 2.5 m but is usually much shorter, with spindly, straight, pale gray stems. Some petals of A. nantucketensis bear 1 or 2 tiny pollen sacs near margins on adaxial surfaces. Petal-borne pollen, which is highly unusual within the plant kingdom, is viable in A. nantucketensis and associated with a unique pollinator guild of native bees (A. C. Dibble et al. 1997). Conservation challenges for this apomictic tetraploid were discussed by Dibble and C. S. Campbell (1995).

Amelanchier nantucketensis has been documented to be self-compatible and able to produce seed asexually (C. S. Campbell et al. 1987).

Selected References

None.

Lower Taxa

None.
1 cm10 mm <br />0.01 m <br /> (5.5 cm55 mm <br />0.055 m <br />) +
glabrous +  and hairy +
Christopher S. Campbell +, Michael B. Burgess +, Kevin R. Cushman +, Eric T. Doucette +, Alison C. Dibble +  and Christopher T. Frye +
E. P. Bicknell +
fissuring in older trees +  and smooth +
salmon colored +, brown +  and gray +
compound +  and simple +
opposite +  and alternate +
rounded +  and cuneate +
4.1 cm41 mm <br />0.041 m <br /> (5.5 cm55 mm <br />0.055 m <br />) +
2.9 cm29 mm <br />0.029 m <br /> (4.2 cm42 mm <br />0.042 m <br />) +
2.9 cm29 mm <br />0.029 m <br /> (4.1 cm41 mm <br />0.041 m <br />) +
elliptic +  and oblanceolate or oblongelliptic +
? (?) +  and ? (?) +
19mm +  and 29mm +
adnate +  and connate +
Nantucket shadbush +
N.S. +, Conn. +, Maine +, Md. +, Mass. +, N.H. +, N.J. +, N.Y. +, R.I. +, S.C. +  and Va. +
not +  and aggregated +
0–400 m +
unisexual +  and bisexual +
not +  and aggregated +
not +  and aggregated +
purplish +  and nearly black pinkish or maroon-purple dark purple-blue or brownish +
0.6 cm6 mm <br />0.006 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
Fields, sand-plain grasslands, heaths, glacial outwash plains, forest openings, disturbed sites, stream shores, among rocks or sand, dry habitats, ditches, swales +
glabrous +  and hairy +
(4-)6-8(-11)-flowered +
3.6 cm36 mm <br />0.036 m <br /> (5.3 cm53 mm <br />0.053 m <br />) +
nodding +, spreading +, drooping +, erect +, ascending +  and arching +
2.4 cm24 mm <br />0.024 m <br /> (3.6 cm36 mm <br />0.036 m <br />) +
crassinucellate +
0 cm0 mm <br />0 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
deciduous +
pinnate +, dentate +, serrate +  and entire +
toothed +, unlobed +  and lobed +
glabrous or +  and sparsely densely hairy +
6-10-loculed +
inferior +  and superior +
biseriate +  and clustered +
collateral +  and basal +
1 cm10 mm <br />0.01 m <br /> (5.5 cm55 mm <br />0.055 m <br />) +
0.45 cm4.5 mm <br />0.0045 m <br /> (0.68 cm6.8 mm <br />0.0068 m <br />) +
0 (?) +  and 4 (?) +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
Pink (?) +, Ivory (?) +  and White (?) +
free +  and distinct +
0.3 cm3 mm <br />0.003 m <br /> (0.45 cm4.5 mm <br />0.0045 m <br />) +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
1.5 cm15 mm <br />0.015 m <br /> (2.2 cm22 mm <br />0.022 m <br />) +
0.9 cm9 mm <br />0.009 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
Flowering Mar–May +  and fruiting Jun–Jul. +
adnate +, free +, connate +  and distinct +
dark purple-blue +
0.75 cm7.5 mm <br />0.0075 m <br /> (1 cm10 mm <br />0.01 m <br />) +
1.4 cm14 mm <br />0.014 m <br /> (3.8 cm38 mm <br />0.038 m <br />) +
0.7 cm7 mm <br />0.007 m <br /> (1.4 cm14 mm <br />0.014 m <br />) +
Bull. Torrey Bot. Club +
4-17-flowered +
not arillate +
0.3 cm3 mm <br />0.003 m <br /> (0.39 cm3.9 mm <br />0.0039 m <br />) +
persistent +
free +  and distinct +
recurved +  and spreading +
triangular +  and lanceolate +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
Endemic +  and Illustrated +
free +  and distinct +
rhizomatous +
erect +  and ascending +
1 +  and 70 +
0.37 cm3.7 mm <br />0.0037 m <br /> (0.43 cm4.3 mm <br />0.0043 m <br />) +
persistent +
connate +  and distinct +
basal +, lateral +, subterminal +  and terminal +
elongate +
0.26 cm2.6 mm <br />0.0026 m <br /> (0.37 cm3.7 mm <br />0.0037 m <br />) +
Amelanchier oblongifolia var. micropetala +
Amelanchier nantucketensis +
Amelanchier +
species +
0 +  and 4 +
inconspicuous +