Zizia aurea (L.) W.D.J. Koch

Common Golden Alexanders


CC = 5
CW = 0
MOC = 71

© DETenaglia

Family - Apiaceae

Habit - Perennial forb with clusters of slightly to moderately tuberous-thickened roots.

Stems - Ascending to erect, to 1.1 m, glabrous or nearly so, sometimes branching.

Zizia_aurea_stem.jpg Stem and leaf sheath.

© SRTurner

Leaves - Alternate and usually basal, the lower leaves long-petiolate, the upper stem leaves short-petiolate to nearly sessile, the sheathing bases only slightly inflated. Basal leaves with the blades 4-14 cm long, 1 or 2 times ternately compound, the leaflets 1-12 cm long, broadly ovate to oblong-obovate or lanceolate, narrowed to rounded (often unequally) or cordate at the base, sometimes with 1 or 2 lobes toward the base. Stem leaves similar to the basal leaves, gradually reduced toward the stem tip, becoming more finely divided with somewhat narrower leaflets and/or segments, the uppermost often only ternately 1-3 times deeply lobed.

Zizia_aurea_leaf1a.jpg Upper stem leaf.

© SRTurner

Zizia_aurea_leaf1b.jpg Lower leaf.

© SRTurner

Zizia_aurea_leaf2a.jpg Leaflet abaxial.

© SRTurner

Zizia_aurea_leaf1.jpg Pressed leaf.

© DETenaglia

Inflorescence - Terminal compound umbels with 10-21 main rays, these to 5.0 cm long, glabrous. Involucre absent. Rays of umbellets to 4 mm long, glabrous. Involucel of 3-9 bractlets, these shorter than the flower stalks, linear, sometimes reduced and fused basally into a low, irregular crown. Flowers 11-19 in each umbellet, the central floret of each umbellet sessile or with a stalk less than 0.5 mm long, the others with stalks 1-4 mm long.

Zizia_aurea_inflorescence.jpg Inflorescence.

© SRTurner

Zizia_aurea_inflorescence2.jpg Inflorescence.

© SRTurner

Flowers - Sepals minute triangular scales. Petals 5, obovate, narrowed or tapered abruptly to a short, slender tip, bright yellow. Stamens 5, alternating with petals, spreading to erect, exserted. Filaments pale yellow, 1.8 mm long. Anthers yellow, 0.3 mm long. Ovaries glabrous.

Zizia_aurea_florets.jpg Florets.

© SRTurner

Zizia_aurea_diagram1.jpg Umbellet. Arrow points to central sessile floret.

© SRTurner

Zizia_aurea_diagram2.jpg Umbellet. Arrow points to central sessile fruit.

© SRTurner

Fruits - Schizocarps 2-4 mm long, ovate to oblong-ovate in outline, flattened laterally, glabrous, the mericarps reddish brown, the 5 ribs tan to yellowish brown, angled and often somewhat corky, but lacking wings.

Zizia_aurea_fruits.jpg Fruits.

© SRTurner

Flowering - April - June.

Habitat - Bottomland and mesic forests, prairies, glades, savannas, streambanks, bluffs, fields, roadsides.

Origin - Native to the U.S.

Lookalikes - Thaspium trifoliatum; also Zizia aptera.

Other info. - The species name aurea means "golden" and the flowers are certainly that. This attractive plant is found across Missouri, less commonly in the Bootheel and the northwestern portion of the state. Beyond Missouri its range includes most of the eastern half of the continental U.S.

Reliable identification of this plant, particularly with respect to its differentiation from Thaspium trifoliatum, is the subject of endless debate. Numerous foliar and floral characters have been utilized, but many of these are difficult to apply, require a particular stage of plant maturity, or are simply unreliable, refusing to correlate cleanly with other attributes. Two features commonly cited as indicating Z. aurea are a sessile central floret in each umbellet, and fruits which are ridged but not winged. The sessile central floret character appears reliable, but is very difficult to interpret in crowded umbellets, and can be misleading in cases where the central floret is lost for some reason. Differentiation from Z. aptera is relatively straightforward, as that species usually has one or more simple basal leaves.

The plant can be quite attractive when in flower, particularly in the colonies that it typically forms. It does well in a garden setting, though it can be quite prolific due to the abundance of seeds it produces. The flowering heads emit a strong odor which some people find disagreeable, a trait shared by Thaspium trifoliatum. The plant has been used in traditional medicine, but most contemporary references list it as toxic. Information on chemical constituents is not readily available.

Photographs taken at the Kansas City Zoo, 5-2-00, and in Eminence, MO., 5-23-03 (DETenaglia); also at Washington State Park, Washington County, MO, 5-03-2014; Shaw Nature Reserve, Franklin County, MO, 6-20-2014 and 5-17-2023; St. Joe State Park, St. Francois County, MO, 5-13-2015; Washington State Park, Washington County, MO, 7-14-2017; and Shut-in Mountain fen, Shannon County, MO, 5-19-2023(SRTurner).