Polygala sanguinea L.

Field Milkwort


CC = 4
CW = 3
MOC = 75

© SRTurner

Family - Polygalaceae

Habit - Annual forb with slender taproot.

Stems - Ascending to erect, to 40 cm, unbranched or few-to several-branched toward the tip, glabrous, not glaucous, green to olive green, carinate to 4-angled near apex.

Polygala_sanguinea_stem.jpg Stem and nodes.

© SRTurner

Leaves - Alternate, relatively closely spaced, sessile or very short-petiolate, linear to linear-elliptic, 1-5 mm wide, glabrous, the margins entire, the plants appearing leafy at flowering and fruiting.

Polygala_sanguinea_leaves1.jpg Stem and leaves.

© SRTurner

Polygala_sanguinea_leaf1.jpg Leaf adaxial.

© SRTurner

Polygala_sanguinea_leaf2.jpg Leaf abaxial.

© SRTurner

Polygala_sanguinea_leaves.jpg Pressed leaves.

© DETenaglia

Inflorescences - Terminal dense headlike or spikelike racemes 1.0-2.5 cm long. Pedicels to 1 mm long.

Polygala_sanguinea_heads.jpg Inflorescence(s).

© SRTurner

Polygala_sanguinea_head4.jpg Flowering head.

© SRTurner

Polygala_sanguinea_head2.jpg Flowering head.

© SRTurner

Flowers - Wings (lateral sepals) 4.5-6.0 mm long, ovate to nearly oval, white, usually slightly to strongly pinkish-tinged toward the tip, often with an inconspicuous slender pale green central band. Corollas zygomorphic, of 3 petals, these 2.5-2.7 mm long, white, usually slightly to strongly pinkish-tinged toward the tip, rarely greenish white, the fused portion 1.5-2.2 mm long. Stamens 8, the filaments fused into a tube just inside the keel that is split longitudinally along the upper side, also fused to the corolla tube, the anthers attached at their bases, usually yellow, the pollen usually shed by apical pores or short slits. Pistil 1 per flower, of 2 fused carpels. Ovary superior, 2-locular, often flattened, the placentation axile (appearing more or less apical). Style 1, often curved toward the tip, usually unequally 2-lobed near the tip, the upper lobe bearing a capitate stigma, the other lobe sterile, with a fringe of hairs. Ovule 1 per locule.

Polygala_sanguinea_flowers1.jpg Flowers.

© SRTurner

Polygala_sanguinea_sepals.jpg External "normal" sepals.

© SRTurner

Polygala_sanguinea_flowers2.jpg Young inflorescence, containing 4 flowers. See discussion below for an explanation of the various structures.

© SRTurner

Fruits - Capsules 2.0-2.5 mm long, obovoid-orbicular, not or only slightly flattened. shallowly notched at the tip. Seeds 1.5-1.7 mm long, the aril 1.0-1.2 mm long, papery, with 2 linear lobes.

Flowering - May - October.

Habitat - Glades, upland prairies, upland forest openings, pastures, fields, ditches, railroads, and roadsides.

Origin - Native to the U.S.

Lookalikes - None.

Other info. - This small but pretty species is found throughout most of Missouri, less commonly in a few south-central and far northwestern counties. Beyond Missouri its range extends throughout most of the Midwest and into New England and Canada. When in flower, the plant is easily identified by its unique inflorescences, which have a tendency to be most strongly pinkish near the apex.

The flowers of Polygala are irregular and unique in morphology, and bear further description. The following was kindly provided by Dr. Richard Abbott, a world expert on this genus: A typical (North American) Polygala flower has three external sepals that are small & greenish, 1 above, 2 below. There are also 2 lateral sepals which are petaloid (expanded and colorful) and often called "wings." There are 3 petals, the upper 2 forming a reduced banner of sorts, which is more or less hidden in our species (esp. those with congested inflorescences). The lower petal is somewhat tubular or even strongly keeled, and in most of our species is crested at its apex. In the case of P. sanguinea the tip of the keel petal & crest is bright yellow. Inside the keel are the 8 stamens, which have the filaments fused into a tubular sheath, and inside that is the single compound ovary of 2 fused carpels.

Certain species of the genus Polygala have been used in traditional medicine. The plants contain saponins and, commonly, calcium oxalate crystals. At one time they were believed to increase milk production in cattle, and this is the source of both the common name and the scientific genus name (Polygala = ancient Greek for "much milk").

Photographs taken at Taberville Prairie, MO., 6-7-03, and at Bethel Prairie, MO., 7-4-03 (DETenaglia); also at Shaw Nature Reserve, Franklin County, MO, 7-22-2008, Crowley's Ridge Conservation Area, Stoddard County, MO, 8-14-2009, Hughes Mountain Natural Area, Washington County, MO, 5-21-2012, Don Robinson State Park, Jefferson County, MO, 6-25-2017, and at Western Star Flatwoods, Phelps County, MO, 6-23-2023 (SRTurner).