Eryngium prostratum Nutt.

Eryngium prostratum plant

Family - Apiaceae

Stems - From slightly thickened roots and a small cormlike base, creeping, repent, herbaceous, to +40cm long, branching, glabrous, ribbed or angled, with a slight carrot fragrance.

Eryngium prostratum stemStem at a node.

Leaves - Opposite sessile or petiolate, variable. Petioles of undivided leaves long, +/-2cm long, glabrous, sheathing at the base, with an adaxial groove. Undivided leaves with the blades ovate to elliptic, sparse coarse serrate, to +2cm long, +1.4cm broad, glabrous, acute. Divided leaves 3-lobed, sessile. Lateral lobes spreading, smaller than the central lobe, elliptic (narrowly), sparse coarse serrate. Central lobe elliptic, acute, sparse coarse serrate. All lobes glabrous.

Eryngium prostratum leaves

Inflorescence - Cylindric pedunculate clusters of flowers, axillary. Peduncle to 3cm long, glabrous, ribbed (carinate). Cluster subtended by an involucre of 5-9 linear to oblong bracts. Bracts typically entire, to +/-1cm long, +/-1.5mm broad, glabrous, spreading to recurved. Cylinder of flowers 7-8mm long (tall), 4mm in diameter. Flowers sessile.

Flowers - Petals 5, purplish-blue, .8-1mm long (unfolded), to .3mm broad, glabrous, apiculate (with the apiculus inflexed). Stamens 5, alternating with the petals, erect, exserted well beyond the corolla. Filaments glabrous, lilac, 1.3mm long. Anthers brownish-purple, .2mm long. Styles 2, spreading, 1mm long, glabrous, purplish-blue at the apex, fading to white at the base, expanded on one side into a green stylopodium, persistent in fruit and elongating slightly. Stylopodia erect and somewhat wrapped around the style, to .3mm long. Ovary inferior, 2-locular. Calyx tube .7mm long in flower, 1mm broad, covered with white glands. Sepals 5, ovate, acute, erect, .9mm long, .6mm broad, glabrous, green at the base, scarious and purple at the apex, accrescent.

Eryngium prostratum flowersFlowers.

Flowering - May - November.

Habitat - Low wet woods, borders of swamps and ponds, moist prairies.

Origin - Native to U.S.

Other info. - This little species can be found in the southeast corner of Missouri. It is an easy species to identify in the field because of its brilliant blue flower spikes. The plant is very small, however, and is often overlooked.
There are two species of Eryngium in Missouri. The other species, Eryngium yuccifolium Michx., does not resemble this species in any way. It is the flower structure that makes these plants similar.

Photographs taken at the Crowley Ridge Conservation Area, MO., 6-14-03.