Thalictrum thalictroides (L.) A.J. Eames & B. Boivin


Thalictrum thalictroides plant

Family - Ranunculaceae

Stems - To +15cm tall, from tuberous roots, herbaceous, often reddish, thin, (+/-1mm in diameter), erect, single or multiple from base. Plant completely glabrous.

Leaves - Opposite. Basal leaves biternate to triternate, appearing at anthesis, petiolate. Petioles to +12cm long. Leaflets shallowly 3-lobed or just notched, to +2cm long, +1.5cm broad. Cauline leaves forming an involucre at base of umble rays, ternate. Leaflets similar to those of basal leaves.

Thalictrum thalictroides plantCauline leaf.

Inflorescence - Terminal umbel with 1-4 rays. Rays to +3cm long, very thin. Single flower terminating each ray.

Flowers - Apetalous. Sepals petaloid, 5-8, typically white to pinkish-lilac, to 12mm long, 6mm broad, glabrous, rounded to subacute at apex, obovate to ovate. Stamens many. Filaments to +/-5mm long, white, glabrous. Anthers yellow, to +1.5mm long. Carpels 4-15. Achenes 8(10)-ribbed, to 5mm long,  2mm in diameter, fusiform, glabrous to pubescent.

Thalictrum thalictroides flowerFlower.

Thalictrum thalictroides fruitsFruits.

Flowering - March - June.

Habitat - Dry open or rocky woods, upland slopes, ridges.

Origin - Native to U.S.

Other info. - This small plant is common throughout Missouri but is easy to confuse with another member of the Ranunculaceae, Isopyrum biternatum (Raf.) T.&G.
They can be differentiate by the following: Isopyrum inhabits low woods and moist soils, has smaller flowers with (nearly always) 5 petaloid sepals, which are always white, and has fibrous roots and alternate leaves.
The plant has also been known as Anemonella thalictroides, and in this case the specific epithet derived from the fact that the leaflets resemble those of the genus Thalictrum, which is also in the Ranunculaceae. "Thalictroides" means "looks like Thalictrum." The specific epithet was retained when the genus of this species was changed to Thalictrum, in accordance with rules of botanical nomenclature.
Steyermark lists three forms for the plant in Missouri. Form thalictroides is the most common and is described above. Form chlorantha Fassett has sepals which are all green and foliaceous. Form favilliana Bergseng is double-flowered with all the stamens and pistils petal-like.

Photographs taken on Coy Bald, Hercules Glade Wilderness, Mark Twain National Forest, Taney County, MO., 4-28-00, at Umstead State Park, NC., 3-23-03, and in Brown Summit, NC., 4-6-03 (DETenaglia); also at Valley View Glade Natural Area, Jefferson County, MO, 4-11-2014 (SRTurner).