Thalictrum venulosum Trel. var. confine (Fern.) Boivin

Boundary Meadow-rue

• State Rank: S1
• Global Rank: G4?
• State Status: Endangered

Habitat: Prairies, thickets, open woods and shores.

Range: Labrador and Quebec south to Maine and New York, west to British Columbia and Yukon Territory, south to New Mexico.

Aids to Identification: Meadow-rues are recognized by their alternate, divided leaves, panicles of yellowish greenish or pinkish flowers with numerous stamens, and leaflets with lobed margins. Boundary meadow-rue has small flowers in a panicle and leaflets with 4 or more lobes. The leaflets have distinct veins. The achenes are curved. It may resemble early meadow-rue (T. dioicum) however the two can be separated based on the length of the petiole of the leaf that subtends the inflorescence. Thalictrum venulosum has a short petiole (up to 3 cm), whereas T. dioicum is longer (up to 6 cm).

Ecological characteristics: Historic locations for this plant have been along river banks in northern Maine.

Phenology: Flowering in June and July

Family: Ranunculaceae

Synonyms: Thalictrum confine Fern.; Thalictrum turneri Boivin.

Known Distribution in Maine: This rare plant has historically been documented from a total of 3 towns in the following county: Aroostook

Reason(s) for rarity: At southern limit of range.

Conservation considerations: Unknown; has not been seen recently. Changes in hydrology along the rivers where a population once occurred may have been detrimental.