Ipomoea macrorhiza Michx.

Wood, John R. I., Munoz-Rodriguez, Pablo, Williams, Bethany R. M. & Scotland, Robert W., 2020, A foundation monograph of Ipomoea (Convolvulaceae) in the New World, PhytoKeys 143, pp. 1-823: 1

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Ipomoea macrorhiza Michx.


74. Ipomoea macrorhiza Michx.   , Fl. Bor.-Amer. 1: 141. 1803. (Michaux 1803: 141)

Ipomoea jalapa var. macrorhiza (Michx.) Ker-Gawl.   , Bot. Reg. 8: t. 621. 1822. (Ker-Gawler 1822: t. 621).

Ipomoea michauxii Sweet, Hort. Brit.   288.1826. (Sweet 1826: 288), nom. illeg., superfl.

Modesta macrorhiza (Michx) Raf.   , Fl. Tel. 4: 76. 1838. (Rafinesque 1838a: 76).

Ipomoea jalapa   forma macrorhiza (Michx.) Matuda   , Anales Inst. Biol. Univ. Nac. Mex. 35: 51. 1965. (Matuda 1966a: 51).


UNITED STATES. In maritimis Georgiae et Floridae, (lectotype P00625543, designated here).


Vigorous trailing perennial of sea shores; stems puberulent, rootstock a stout tuber. Leaves petiolate, 4-18 × 4.5-17 deltoid in outline, 3-lobed or (less commonly) entire, obtuse to shortly falcate-acuminate, base truncate and then cuneate onto the petiole, margin undulate to serrate, adaxially minutely punctate, thinly pubescent, glabrescent, abaxially grey-tomentellous; petioles 1.5-9.5 cm, pubescent and sometimes muricate. Inflorescence of few-flowered axillary cymes, flowers often solitary; peduncles 1.3-10 cm, tomentose, glabrescent; bracteoles caducous, not seen; secondary peduncles 7-24 mm; pedicels 10-30 mm, thickened upwards; sepals obtuse, sometimes mucronate with a broad point, tomentellous, unequal, outer oblong-lanceolate, 13-15 × 4-5 mm, inner oblong-ovate, 14 -16 × 6-7 mm, the margins glabrous, scarious, strongly accrescent in fruit to 22 × 10 mm; corolla 10-11 cm long, white with a pink throat, tomentellous on mid-petaline bands, tube cylindrical and only slightly widened for c. 5 cm, then abruptly flared and funnel-shaped, limb c. 8 cm diam., apparently entire. Capsules 15-20 × 12-15 mm, ovoid with short persistent style, glabrous; seeds 12 × 5 mm densely lanate with hairs 10-15 mm long.


Figure 49 View Figure 49 .


Endemic to the south eastern coasts of the USA from North Carolina to Florida and west to Mississippi.

UNITED STATES. Alabama: J.R. McDonald 9845 (IBE, MO). Florida: Genelle & Fleming 351 (BM, USF); F. Rugel 1845 (BM); A.H. Curtiss 2165 (BM, K); T. Nuttall (OXF). Georgia: W. Faircloth 5388 (GA). Mississippi: Pearl River, sine data (FSU); Jackson, R.L. Diener s.n. (MISSA). North Carolina: C. Ritchie Bell 18568 (UNC, BM). South Carolina: S.W. Leonard 4321 (UNC, S).


In designating a lectotype, we have chosen the only original specimen at Paris with a corolla.


A coastal species resembling Ipomoea jalapa   but differing in the more hirsute, usually 3-lobed leaves and white, usually solitary flowers as well as the distinctive habitat. It is reported to be a night-flowering moth pollinated species (Austin and Huáman 1996).