| Author | (Nuttall) Rydberg | |
| Distribution | Of historical occurrence, and might well be extirpated in NC. A specimen was collected in Sawyersville, Haywood County, on 17 July 1891 (specimen at NCU).
This is a species with a rather limited range, essentially west of the Appalachians. It occurs mostly from OH west to southeastern IA, and south to northern AL and northern AR. There are a few records from southwestern VA and northwestern SC, but it seems to be extirpated in VA, NC, and SC. | |
| Abundance | The NCNHP considered it simply as "historical" (SH), but that appears to be very conservative. In reality, it is best to consider it as extirpated from NC, and the editors chose to rank it a SX, with very little chance of re-discovery. It is listed on the state protected list as Special Concern - Historical. | |
| Habitat | This is a species of high pH soil, both in upland forests and in prairies. Habitats can include barrens, calcareous woodlands, and similar sites on circumneutral soils (of course, this refers essentially to habitats west of the Appalachians). | |
| Phenology | Blooms from June to August, and fruits from August to October. | |
| Identification | This is a fairly robust legume, growing to 2.5-3 feet tall, either unbranched or with a very few branches. The few leaves are divided into three leaflets, and each is about 2.5-3 inches long and about half as wide, being ovate in shape. The several flower clusters are in narrow racemes, on stems up to about 3-4 inches long, but carried below the leaves. The racemes are very densely packed with small blue or lavender-blue flowers, and each cluster is about 2 inches long. The extinct O. macrophyllum was somewhat similar but had wider leaflets, about 2/3 as wide as long, and the bases of the leaflets were subcordate instead of rounded in O. onobrychis. Though this species could easily be overlooked by Carolina observers as some other legume if seen only in leaf, particularly as a Desmodium, if ever found with flowers, the blue "spikes" of flowers on a fairly tall legume with large trifoliate leaves should catch the attention of the observer. In February 2023 Eric Ungberg examined the Haywood Co. specimen and reported that the seeds are much darker, grayer, and a little smaller than those of specimens elsewhere in the range--local variance or a taxonomic entity? | |
| Taxonomic Comments | Formerly named as Psoralea onobrychis.
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| Other Common Name(s) | French-grass (a highly idiosyncratic name, to mislead non-biologists into thinking it might be a grass or a non-native species). Why so many references use this name is a mystery. Peterson and McKenny (1968) named it as Sainfoil. | |
| State Rank | SH [SX] | |
| Global Rank | G5 | |
| State Status | SC-H | |
| US Status | | |
| USACE-agcp | | |
| USACE-emp | | |
