Microthlaspi perfoliatum (L.) F.K. Mey.
Family - Brassicaceae
Stems - To +30cm tall, glabrous, glaucous, herbaceous, erect or branching above, from long taproot.
Leaves - Basal leaves in rosette, petiolate. Petiole to 2cm long, glabrous. Blade to 3cm long, 1.5cm wide, ovate, elliptic or oblong, glabrous, coarsely toothed. Cauline leaves clasping, auriculate, glabrous, glaucous, entire to coarsely toothed, reduced upward.
Leaf, not truly perfoliate
Cauline and basal leaf respectively.
Inflorescence - Terminal raceme. Compact in flower, becoming elongated in fruit to +10cm. Pedicels to 4mm long in flower, expanding in fruit to 6mm, filiform, glabrous.
Inflorescence top view
Flowers - Petals 4, white, glabrous, spatulate to oblanceolate, to 2.5mm long, 1mm broad. Stamens 6, didynamous. Filaments 1.2mm long, glabrous, white. Anthers yellow, .2mm long. Style 1, very short, to .2mm long. Ovary green, superior, compressed, ovoid to rotund, 1mm long. Sepals 4, distinct, to 1.5mm long, 1mm broad, green with whitish margins, subacute at apex, ovate-oblong. Silicle to 6mm long, winged, obcordate, notched at apex, glabrous.
Flowering - March - May.
Habitat - Roadsides, waste ground, rocky outcroppings and open ground.
Origin - Native to Europe.
Other info. - Yet another
one of the introduced plants from the Brassicaceae
which dominate the early springtime. The stems of this plant appear to
pass through the leaves, hence the name "perfoliatum" from "perfoliate." In truth, the leaves are not perfoliate but instead merely strongly clasp the stem, bearing prominent auricles.
"Thlaspi" comes from the Greek name of cresses - "thlaspis" - with "micro" denoting a diminutive form.
Photographs taken at Eagle Bluffs Conservation Area, Boone County, MO., 3-7-04 (DETenaglia); also near Labadie, Franklin County, MO, 3-30-2015 (SRTurner).