Tall Meadow Rue is a stout, native, erect perennial forb reaching from 3 to 5 feet in height, the mature stem is a purple color. The stem may be smooth or have fine whitish hair. It usually branches near the top.
Leaves: The leaves are compound - 3 to 5 times 3-parted, variable in size - up to 2-1/2 times as long as wide but can also be slightly wider than long - and are alternate on the stem. The lower leaves are on a stalk and upper stem leaves are stalkless and less developed. Leaf stalks are usually smooth. A mature leaf will have 81 leaflets. Leaflets are stalked, usually have 3 rounded to bluntly pointed lobes and are hairy under (but without glandular hair). Veins are prominent on the under side of the leaflet. A sheath is formed where the leaf stalk meets the stem.
The inflorescence is a pyramid shaped compound panicle branching from the top of the stem. Sometimes there are smaller panicles rising from the upper leaf axils. Plants are dioecious, that is male and female flowers are on separate plants. Male plants have the larger and most showy flower clusters.
Flowers: The male flowers are small 1/3 inch long 4 (to 6) -parted, white to greenish lance shaped sepals with up to 15 stamens that are club shaped and have a pointed tip (are apiculate). The filaments of the stamens are white while the anthers are yellow, turning darker after pollen release. Female flowers have light green pistils and very fine surface hair. In the Thalictrum species the stigma extends down the side of the style. The sepals fall away early, no petals. Stems of the flowers and the flower panicles are usually without hair.
Fruit: Seeds are a dry ovoid dark brown achene, which is ribbed (veined), may be hairy or glandular, the ribs appearing as longitudinal wings. There is a beak on the seed at first, as long as the achene body, which separates away as the seed matures. The achene body is 2 to 4.6 mm long. Seeds require 60 days of cold stratification for germination.
Habitat: Tall Meadow Rue grows in meadows, open woods, and prairies where the soil is loamy to sandy, moist to mesic and with full sun to partial sun. Roots are tuberous.
Names: The genus, Thalictrum, was originated from the Greek word 'thaliktron' by the Greek pharmacologist Dioscorides, who used it to describe plants with divided leaves. The species name, dasycarpum, is from two Greek words, dasy, meaning 'hairy or thick' and carpus, meaning 'fruited' - here referring to the carpel, the seed organ of this species. The author name for the plant classification covers two individuals who both made contributions to the classification -"Fisch' is for Friedrich Ernst Ludwig Fischer (1782-1854), Russian botanist and director of the St. Petersburg Botanical Garden and 'Ave-Lall.' is for Julius Leopold Eduard Ave-Lallemant (1803-1867), a German botanist who also worked in St. Petersburg.
Comparisons: The two other species that will resemble Tall Meadow Rue are the Early Meadow Rue, Thalictrum dioicum, which grows shorter and in less sunny locations and the leaves have more numerous rounded teeth, not just 3 lobes; and Veiny Meadow-rue, T. venulosum, which grows in the same habitat as Early Meadow-rue, and has similar leaves. Both have achenes that are different from each other and from T. dasycarpum. Veiny has rhizomatous roots and Early has fibrous roots. Veiny Meadow-rue is known to hybridize with Tall Meadow Rue.
Above: This plant with male flowers is in bloom mid-June to early July. There are no petals and the greenish-white sepals drop away early. Note the purple stem of the mature plant.
Below: 1st photo - the male flower stamens have white filaments and note the pointed tip on the anthers. 2nd photo - leaflets mostly have 3 pointed lobes and no glandular hair on the underside.
Below: 1st photo - The female flowers consist of a group of light green pistils with styles. 2nd photo - The fertilized flowers with the ovary expanding and styles drying off - fine hair overall.
Below: 1st photo - Seed development in the green state - the beak is still attached to the forming seed, the ribs are formed and fine hair persists. 2nd photo - Dry mature seeds.
Below: 1st photo - Flower buds and leaf buds opening atop the very sturdy stem which is green at this stage, turning purple later. 2nd photo - The leaf of Tall Meadow Rue is 3 to 5 times 3-parted usually yielding 81 leaflets. Upper leaves attach directly to the stem and are less developed, lower leaves have stalks. 3rd photo - The leaf stalk forms a sheath where it joins the stem.
Below: Comparison drawing of Tall Meadow-rue (1st drawing) and Early Meadow-rue (2nd drawing). Note the differences in the leaflets and especially in the achene. Both drawings from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Notes: Tall Meadow Rue is indigenous to the Garden. Eloise Butler catalogued it on May 25, 1907. It was also listed on Martha Crone's 1951 inventory of plants in the Garden at that time, and on each later census. This species is native to Minnesota, being found in all but a dozen counties, which exceptions are mostly in the western section of the state. Its native range in North America is the entire area except for the eastern coastal states and the southwestern coastal states.
Thalictrum is a large genus with almost 200 species worldwide, with 22 in North America. There are 5 species of the genus Thalictrum found in Minnesota, the three mentioned up above plus one other meadow rue - T. revolutum, the waxy-leaf meadow-rue (from northern MN and is considered quite rare, if still present). The fifth species is the Rue Anemone, T. thalictroides. Subspecies are not recognized.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"