Vascular Plants of North Carolina
Account for Whorled Milkwort - Polygala verticillata   L.
Members of Polygala with account distribution info or public map:
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Section 6 » Order Polygalales » Family Polygalaceae
AuthorL.
DistributionScattered over the mountains and Piedmont, but only a few Coastal Plain records.

This is a somewhat Northern species, ranging from ME and MI south to NC and TN. The range in NC and the East is somewhat clouded by the similarity of this species and P. ambigua in collections.
AbundanceUncommon to infrequent in the mountains and Piedmont, and not obviously scarce in the central and western Piedmont like P. ambigua; very rare in the Coastal Plain. This species and P. ambigua are somewhat similar in abundance in the mountains and eastern Piedmont, but the other species is barely known elsewhere in the Piedmont and in the Coastal Plain.
HabitatThis species and P. ambigua have very similar habitat requirements -- dry soil in sunny situations, apparently favoring somewhat circumneutral soil. There must be some slight distinctions in habitats between these two, but such has apparently not been described.
PhenologyBlooms from June to September, and fruits soon after flowering.
IdentificationThis species is very similar to P. ambigua. Both are very slender, with some branches, and an erect stem only to 8-9 inches tall. However, this species has most or all stem leaves in whorls of 2-5 leaves, though some upper leaves might be alternate. All leaves are linear, about 2/3-inch long and very narrow. More conclusive is that in this species, the numerous terminal racemes are less than 3/4-inch long, often around 1/2-inch long, and quite narrow. Those of P. ambigua average 1-2 inches long; each has numerous small greenish-white to whitish flowers. In this species, the falling fruit leave the cluster still compact, without gaps; in P. ambigua, the falling fruit are more scattered and the cluster has gaps within it. Each species can be easily overlooked, and you will certainly need the narrow spike/racemes of small flowers to help detect them.
Taxonomic CommentsP. ambigua was often included within this species, as a variety, though most references now have them split as species. To further confuse matters, Weakley (2018) lists two varieties -- var. verticillata, which is widespread over the state, and var. isocycla, whose range in the state is unknown, based on specimen data.

Other Common Name(s)None
State RankS3
Global RankG5
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Harry LeGrandphone line clearing on mafic soil; Durham County; 28 June 2020 DurhamPhoto_natural
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