Microthlaspi perfoliatum (L.) F. K. Mey.
Family: Brassicaceae
claspleaf pennycress
[Noccaea perfoliata (L.) Al-Shehbaz,  more]
Microthlaspi perfoliatum image
Stems unbranched or branched basally or distally, (0.3-)0.5-2.8(-4) dm. Basal leaves (not rosulate or loosely so); petiole 0.5-1.3 cm; blade ovate or broadly elliptic, 0.3-2(-2.7) cm × 2-10 mm, base cuneate or attenuate, margins entire or, rarely, obtusely and sparsely dentate, apex rounded. Cauline leaves: blade ovate-cordate or suboblong, (1-)2-4(-5.5) cm × (2-)5-15 (-20) mm, base cordate-amplexicaul, margins entire or repand, apex obtuse. Fruiting pedicels (2.5-)4-6 (-8) mm. Flowers: sepals (0.8-)1-1.5(-2) × 0.5-1 mm, (margins white); petals 1.5-3.5(-4.7) × 0.5-1.3 mm; filaments 1-1.5(-2) mm; anthers 0.1-0.2 mm. Fruits 3-6.5(-8) × (2.5-)3-6(-7) mm, base obtuse, apical notch 1-1.5 mm deep; wings 1-2 mm wide apically, much narrower basally; style obsolete or 0.1-0.3 mm. Seeds yellow-brown, 0.9-1.3(-1.5) × 0.7-1 (-1.2) mm. 2n = 14, 28, 42. Flowering Mar-May. Waste grounds, roadsides, fields, plains, thickets; 0-500 m; introduced; Ill., Ind., Kans., Ky., Md., Mo., N.J., N.Y., N.C., Ohio, Pa., Tenn., Va., Wash., W.Va.; Europe; Asia; n Africa.
From Flora of Indiana (1940) by Charles C. Deam
This species was found in 1924 by Miss Edna Banta of Brooksburg, Jefferson County, who reports it to be a frequent to common weed between Brooksburg and Madison, a distance of 8 miles, and in other places in the county. Reported also as occurring on the campus of the University of Notre Dame, St. Joseph County.
Annual herb with a long taproot 10 - 30 cm tall Stem: upright, branched above, with a waxy coating (glaucous). Flowers: in compact, branched clusters (racemes), which are borne terminally on the stems. Flower stalks to 4 mm long (longer in fruit). Sepals four, ascending, green with whitish margins, to 1.5 mm long, to 1 mm wide. Petals four, white, 2 - 3 mm long. Stamens six. Anthers yellow. Fruit: a pod (silicle), 4 - 7 mm long, egg-shaped with narrowed base and rounded tip, tips notched (wider than deep), winged. Fruit stalks horizontally spreading, to 6 mm long. Seeds two to four per chamber. Basal leaves: in a rosette, stalked, to 3 cm long, to 1.5 cm wide, egg-shaped or oblong or elliptic, coarsely toothed. Leaf stalks to 2 cm long. Stem leaves: alternate, stalkless, clasping, 1 - 3 cm long, progressively reduced, egg-shaped to oblong egg-shaped with rounded lobes at the base, sometimes coarsely toothed, with a waxy coating (glaucous).

Similar species: No information at this time.

Flowering: June to July

Habitat and ecology: Introduced from Eurasia. An uncommon weed of roadsides, railroads, waste ground, fields, and disturbed areas.

Occurence in the Chicago region: non-native

Etymology: Thlaspi is the Greek word for cress. Perfoliatum means "with the leaf surrounding the stem."

Author: The Morton Arboretum

Annual 1-3 dm; cauline lvs sessile, ovate or ovate- oblong, 1-3 cm, entire or with a few teeth, the basal auricles blunt or rounded; pet 2-3 mm; mature pedicels horizontally spreading; frs obovate, 4-7 mm; convex below, the wing gradually widening to the summit, the wide open notch ca 0.5-1 mm deep and 1-2 mm wide; seeds smooth, 2-4 per locule; 2n=14, 28, 42, 70. Native of Eurasia, now found in fields, roadsides, and waste places here and there in our range. Apr., May.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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