Vascular Plants of North Carolina
Account for Lowland Loosestrife - Steironema hybridum   (Michaux) Rafinesque ex B.D. Jackson
Members of Primulaceae:
Members of Steironema with account distribution info or public map:
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Section 6 » Family Primulaceae
Author(Michaux) Rafinesque ex B.D. Jackson
DistributionVery widely scattered over much of the state, from the coast to the Mountains. Specifically, records from the southern half of the Mountains, a portion of the northern and central Piedmont, and a few coastal counties. Seemingly absent from most areas of the state, though with the potential to be found anywhere! The Halifax County record was collected in 2022; specimen URV 1357 [University of Richmond herbarium].

This species, which is not a hybrid, has a wide range over much of the county but is not numerous in most areas. It ranges from eastern Canada south to northern FL and OK.
AbundanceRare in the southern Mountains; very rare to rare in the central Piedmont; and very rare in coastal areas. The species is probably being overlooked by collectors and other biologists, though it clearly is a rare species in most of the East. It is a State Significantly Rare species, with a State Rank assigned by NCNHP as S2?. As much as the website editors may dislike using a "?" on a rank, this S2? rank does seem appropriate for such a species with records across the state but with huge holes.
HabitatThis is essentially a wetland species, favoring marshes, wet meadows, ditches, wet spots in powerline clearings, margins of pools, openings in bottomlands, and other partly sunny to sunny damp ground.
PhenologyBlooms from June to September, and fruits from September to October.
IdentificationThis is a medium-sized herb, with an erect stem averaging about 2 feet tall, with no creeping rhizomes (underground). It has an often swollen stem base, usually wider than 1/6-inch across; the very similar S. lanceolatum has a very slender stem, with long and creeping rhizomes. It has numerous opposite leaves, each with a distinct but fairly short petiole of about 1/4-inch long; the leaf base is distinctly rounded such that the petiole is distinct. The leaf blade is lanceolate, entire, about 2 inches long and 1/3-inch wide, with a tapering tip. S. lanceolatum has the leaf base gradually tapering to the stem, almost appearing without a petiole. The inflorescences of each of these two is very similar, consisting of one or two flowers in each of the upper leaf axils; the yellow flowers are similar to those of others in the genus, and about 3/4-inch across. This species can generally be separated from S. lanceolatum by habitat, as S. hybridum is essentially limited to wetlands, whereas S. lanceolatum typically grows in high pH soil in uplands, such as in glades, open woods, wooded borders, and roadbanks. Be careful in the separation of these two narrow-leaved species, as neither is common, and S. hybridum is quite rare. The obvious petiole and rounded leaf base of S. hybridum, a thicker stem at the base and a taller stem, wetland habitat, and lack of a creeping rhizome should help in its separation from S. lanceolatum and others in the genus.
Taxonomic CommentsSome references in the past, if not today, treated this as a variety of Lysimachia lanceolata, as L. lanceolata var. hybrida. Most seem to acknowledge that not only is this not a hybrid, but it is a distinct and good species. These species have now been moved to their "old" genus by Weakley (2020) -- see below.

Weakley (2020) has split out Steironema from Lysimachia based on a 2018 paper using molecular research; and in so doing has gone back to "old" taxonomy. In Lysimachia there are no staminodes and the leaves are punctate with elongate markings (vs. staminodes present and punctae absent in Steironema).
Other Common Name(s)Hybrid Loosestrife, Lowland Yellow Loosestrife, Mississippi Loosestrife
State RankS2?
Global RankG5
State StatusSR-P
US Status
County Map - click on a county to view source of record.
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B.A. SorriePhoto taken 1990, Middleborough, MA. Photo_non_NCPhoto_non_NC
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