Vascular Plants of North Carolina
Account for Lanceleaf Loosestrife - Steironema lanceolatum   (Walter) Gray
Members of Primulaceae:
Members of Steironema with account distribution info or public map:
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Section 6 » Family Primulaceae
Author(Walter) Gray
DistributionPresent over most of the Mountains and Piedmont; probably does not occur in the Coastal Plain, though occurrences in Halifax and Nash counties are along the Fall Line.

This is a widespread species of the Eastern and Central states, ranging from PA and WI south to the FL Panhandle and northeastern TX.
AbundanceFairly common in the southern Mountains, but rare in the northern ones; uncommon to infrequent in the Piedmont, most numerous in the north-central portions.
HabitatThis species has a wide array of habitats, though it prefers high pH soil of dry to mesic sites, but always in open to partly open sites. It occurs most often in glades and barrens, dry to mesic wooded margins, powerline clearings, and other such places over mafic rocks. However, in many areas it does range into bogs, ditches, damp ground along streams, and other wetlands. As S. hybridum is essentially limited to wetlands, this very similar species could grow in similar places as S. lanceolatum, and thus care is needed in their identification.
PhenologyBlooms from May to August, and fruits from September to October.
IdentificationThis is a fairly small herb, with an erect to leaning stem averaging about 1-1.5 feet tall, with creeping rhizomes (underground). It has a narrow stem base, usually narrower than 1/6-inch across; the very similar S. hybridum has a thicker stem (usually wider than 1/6-inch), with no creeping rhizomes and is usually a taller and clearly erect species. S. lanceolatum has numerous opposite leaves, each with the leaf base gradually tapering (cuneate) to the stem, such that a petiole is not apparent. The very similar S. hybridum has the leaf blade clearly rounded at the base 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. 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. hybridum by 1) a slender stem that is somewhat short (often barely 1 foot tall), 2) a creeping rhizome, and 3) a tapering leaf base such that no petiole is apparent. This species should not be overly hard to find in the southern mountains, but in the Piedmont you likely will need to confine your searches to known areas of high pH soil. It usually grows in dense patches, often to the exclusion of other species.
Taxonomic CommentsWhen Lysimachia hybrida was included with this species, L. lanceolata was listed in references as L. lanceolata var. lanceolata. Nearly all recent references treat these as separate species. Now, Weakley (2020) has moved these species into their "old" genus (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)Lanceleaf Yellow Loosestrife
State RankS3 [S3S4]
Global RankG5
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B.A. SorriePiedmont, Iredell soil area S of Carbonton, edge of dirt road, June 2015. MoorePhoto_natural
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