Zigadenus – Back to Basics

If you’re reading this, I’m guessing you may already recognize Zigadenus.  It thrives in moist to very wet soils, often around the edge of swales that are intermittently inundated.  In the Apalachicola flora, to the wet side, you’ll find Sarracenia flava, and to the dry side, Liatris spicata; it’s associates being the suite of spectacular bog to wet soil plants so common in open areas here.  There are seldom just a few Zigadenus at a site; if you find one, it’ll likely be one of many.  Moreover, there is a logical tendency for clustering based on the rhizomatous growth habit. A flowering stem terminates growth of each ramet, at the base of which one to several buds are formed to carry on the following season.

One of several buds formed along the rhizome, basal to the current season’s growth

But not every likely site is populated by Zigadenus; there are large stretches of seemingly perfect habitat where the plant will not be seen, particularly closer to the shore. When I venture up Florida SR-65 from the coast, 15 miles of highway stretch between US 98 and the first sitings of this plant – just south of the Apalachicola National Forest boundary.

Zigadenus vegetative growth

In flower, it’s pretty simple to identify Zigadenus, unless you’ve run into a population of Veratrum virginicum. When totally vegetative, identification takes a bit of experience.  In spring and the earliest summer, the plant masquerades as a sedge; at least, that’s my way of describing it.  Having died back over winter, new foliage emerges early in spring, giving an appearance more like that of a giant, glaucous sedge than a relative of Osceola’s Plume.  The blades are conduplicate, or at least canaliculate, which is jargon for being folded along the mid vein; a cross-section would show a v-shaped cut.  They maintain the v-fold along the mid-vein, flattening out toward the margin – so the cross-section takes the form of a folded paper plane.

The leaf margin is practically entire, made razor-like by a cuticular edge, and presence of minuscule hyaline projections, not denticulations as much as tiny hairs or enations – giving the sensation of a toothed edge when a finger is run the length of the tapering blades.  It reminds me of the leaf margins on sugar cane.

The young plant is truly sedge-like, and to my eye, the leaves are 3-ranked.  There’s certainly either a twisting in the stem or a spiraling phyllotaxy that organizes the coarse leaves in an open, loosely triangular arrangement.  The base of the flowering stem is, in cross-section, rounded “triquetrus” – three sided, a phyllotaxy reflected in foliage bases also.

Basal stem x-section
Cross-section of leaf bases, showing triangular form

With a strong glaucous abaxial surface, the new leaves produce an effect of narrow silver swords arching stiffly upward.  It’s a distinct element among the finer texture of grasses and softer foliage of orchids, aletris, rhexias, and daisies.

By early summer, glabrous and glaucous flowering stalks begin to emerge, headed strictly upward for 0.8 to 1 m (2-3 feet) before branching and forming buds, often topping out well above a meter.  The stem is outfitted with several non-sheathing leafy bracts, sequentially diminished in size.

The small cream-colored (reddish-apiculate) buds, glaucous when young, are subtended by a large, reddish sheathing bract and a smaller upper bract. 

Bud development and flowering are acropetal (proceeding from lower to upper buds), with 7-15 buds forming on each branch.  The color scheme for buds and open flowers is creamy white with accents in rusty red-pink and shades of olive green.  I’ve examined hundreds of flowers and glanced over numerous populations and have not yet encountered any forms deviating from this color palette. 

The individual flower, which seems to remain receptive for at least two days (untested), forms atop its inch-long, wax-like pedicel, defined by 6 spreading tepals, 3 smaller, somewhat strap-shaped sepals and 3 more contoured (subtly clawed) petals, both of a firm, waxy texture and about 1.5 cm long, with entire margins and apiculate tips. 

Showcasing the differential shapes of sepals vs. petals (the lower, clawed segment)

Their smooth texture contributes to a sense of cleanness, emphasized by the specific epithet “glaberrimus”  Each tepal bears a basal pair of conspicuous round, ochre-green glands (more prominent on petals), up to 2 mm across, positioned at the broadest region of the segment, just beneath the position of ripe anthers and receptive stigmas.  This defining feature is the basis for the generic name, zygos for yoked (paired) and aden for gland.

Zigadenus flower, showing differential aging of the two anther tiers.

Rising at the center is a column formed by two sets of 3 stamens, closely gathered yet not connate.  Each succulent filament arches over, terminating in a large, short anther that opens freshly as rusty gold, fading darker.  The two sets of anthers are slightly tiered, and often not synchronous; it’s common to encounter a flower with one tier withered while the other remains fresh.  Fountain-like, the three styles emerge from the center, each terminating one of three very loosely connate carpels that are completely obscured by stamen filaments. 

An older flower, with anthers having coiled upward

Observing flower development of Zigadenus, there seems to be a protandrous strategy. Anthers of fresh flowers are positioned over the tepalar glands, with styles not so visible.  Later in flowering, the anthers turn upward and the styles reposition such that the stigmas are more present.  This, however, is variable; I’ve seen flowers with fresh pollen borne on straight anthers. Clearly, however, pollinators dance around the perianth platform, contacting anthers and stigmas while probing the glands.

Flower with 3 anthers still showing fresh pollen
Flower with anthers past performance, turned upward

The developmental sequence is quite a performance.  It must be similar to development of the closely related Veratrum virginicum, which I’ll have to study next year. Below are photos of the only population I’ve encountered (to date) of Veratrum. Studying these plants causes me to wonder about justifications for maintaining Zigadenus and V. virginicum in separate genera; they share the curious vegetative habit and leaf structure, the two tiers of stamens that mature separately, and the characteristic tepalar paired glands.

Veratrum virginicum, see the pistil profile in the lower left flower
Veratrum virginicum flower, showing stamens
Veratrum virginicum inflorescence, slightly more open than Zigadenus, flowers smaller

The closest (unrelated) parallels to this floral form that come to mind are both dicotyledonous, with Frasera flowers I saw in Missouri being remarkably reminiscent of those in Zigadenus due to the basal glands (though in Frasera, these are more like ciliate pads for landing).  


The other parallel comes with Passiflora, not simply because the anthers and stigmas arch over, but because they change position through anthesis.

Zigadenus glaberrimus though not subject of many publications, has been known under the same name since Michaux’s description and illustration, published in the 1803 Flora Boreali-Americana.  There’s no trail of synonymous names. 

Zigadenus distribution, figure 2, borrowed from Zomleter, McKain, and Rentsch, 2014.

There is, however, a biogeographic trail, the plant being known from populations as far north as the Virginia Coastal Plain.  Populations are vouchered in coastal North and South Carolina (which is where Michaux made his collections), sweeping down to a western limit in Eastern Louisiana. 

County Distribution Map from ISB Plant Atlas

In Florida, plants are reported only west of Jefferson County, with no recorded presence on the Atlantic Coast, or in adjacent Georgia.  Zigadenus reflects some ancient geography, following contours of the Suwannee Trough, seemingly absent from the Okefenokee Plains and Sea Island areas of the Coastal Plain.  

The Back Story
Over the past several decades, there have been changes as to how limits of related genera in the Melanthiaceae are interpreted.  Chapman recognized both Amianthemum and Stenanthium as separate genera, but included a second Southeastern species (by Asa Gray) in the genus, Zigadenus leimanthoides.  That taxon is not native to Florida, and is now considered a Stenanthium.  Small, 1903, treated Zigadenus (which he, Chapman and most earlier authors spelled as Zygadenus) as monotypic. 

Small’s 1903 entry for Zigadenus

Clewell accepted an expanded Zigadenus (based on a 1961 article by Kupchan, Zimmerman, and Fonso in Lloydia, which I haven’t been able to access.)  His treatment folded Crow Poison, Stenanthium densum, and Fly Poison,  Amianthemum muscaetoxicum, into Zigadenus.  If you check Flora of North America, you’ll find researcher Kayla Swartz supported this much expanded Zigadenus, encompassing 14 species, many from Western North America.  
Checking both Kew’s Plants of the World OnLine (POWO) and the ISB Plant Atlas, you’ll discover these resources accept the tightly limited definition of Zigadenus as monotypic, embracing only the single, original Michaux species Z. glaberrimus – the type for the 1803 genus.  This reset came with a 2002 publication by Zomlefer and Judd – ‘Resurrection of Segregates of the Polyphyletic Genus Zigadenus s.l. (Liliales: Melanthiaceae) and Resulting New Combinations’, confirming by 2014 that a difference in base chromosome number is just one of many distinctions that set Zigadenus apart from other related groups.

Page 213 of Volume 1, Michaux’s Flora

Florida naturalists may give little daily thought to André and François André Michaux, but reading James Reveal’s considerable discussion “No Man is an Island…” would bring new appreciation for what André, indeed what the father-son team accomplished in America, and for their impact on the history of Florida plant discovery.  Following the American Revolution, and based on a moment of warm relationship between France and the new American Republic, the King’s Botanist, André Michaux, his 15-year-old son/apprentice François André, gardener Paul Saunier, and Jacque Renaud (a “domestic”) journeyed to New York, arriving 13 November 1785.  Making contacts with necessary politicians and with William Bartram (John Bartram had died nearly ten years before), funded through the French government, Michaux established a 30-acre garden New Jersey.  But the Michaux team would not linger in the Northeast, rather they travelled to Charleston (which, under British rule had been Charles Town), South Carolina, where Michaux acquired a 111-acre parcel near Ten Mile Station.  This would be the principle garden and base of operation during their stay in America.
The reasoning for this location might have been nearness to greater stands of old-growth forest, timber being of prime interest to France, and therefore to Michaux.  The location, though serviceable, wasn’t as easy for shipments to France as things might have been in the Northeast, yet still, within weeks the team began to ship seed and plants to French authorities.  Indefatigable might be the word, but however one elects to describe André Michaux, he seems born to the task of field exploration and plant culture. Making what must have been exhausting journeys deep into the Appalachians and along the coast to Savannah, and even to Florida and the Bahamas, he would also return to the Northeast to check in on activity at the garden in Bergen, New Jersey, and had the political sense to check base with French authorities, who were still funding his activities.

Circumstances changed, however, with the beginnings of a French Revolution.  By 1790, François André (who was just now 19, and had been wounded in his eye from a hunting accident) returned to France.  With the French royal system unravelling, by 1792 the project was officially ended, garden properties were sold (Michaux purchased the Charleston property personally) and support ended.  Michaux was to return to France, a repatriation he delayed until 1896. All the while his explorations, and pleas for support to American sources, and his hope for support from the new French government continued.  Field trips to Canada, reaching Hudson Bay, to Kentucky and Tennessee, and later to Illinois and the Mississippi River meant that by his return to France, André Michaux had covered more of Eastern North America, and had a greater appreciation of the flora than any human who had ever lived.  

Defying fate one last time, on his return voyage Michaux and his collections of seed and specimens were shipwrecked, washing ashore in on an October day in Holland. Unconscious, but rescued, Michaux would find his plants, papers, and journals had been salvaged.  Arriving in France, he learned that most material he had sent to the Royal Gardens was now lost.  But he and François were alive and driven; work continued.  Michaux was something of a celebrity, and it seems appreciation was sufficient for his being awarded a position and salary. This was a productive period, during which Michaux authored a book on Oaks of North America and completed much of his work on the Flora, all of which was left in the hands of François and botanist Louis Claude Richard, as Michaux struck out on his final set of ventures from France in 1800 – never to return.

Richard, working with François, was left to complete eiditng the Flora and oversee publication. Reveal seems a bit critical of freedoms Richard might have exercised in this regard, but there were similarities in the histories of the two botanists and collectors. Both had just returned to a France in the throes of revolution after years collecting and studying plants in foreign countries. Both were adventurous and persistent. And both merit credit for the Flora.
The legacies, not as great as might have been had he live past 56 years of age, are yet astonishing.  Having worked from his base in coastal South Carolina, Michaux’s contributions to the SE Coastal Plain flora, along with the work of John Fraser (who briefly connected and collected with the Michaux team) to convey and complete Walter’s Flora Caroliniana), provide much of the foundation for taxonomy of the Apalachicola flora.  Of course, the rationale for including this history stems from Michaux’s publication of Zigadenus glaberrimus in vol 1 of the 1803 Flora Boreali-Americana, a description complete with an illustration by P. D. Redouté.

André Michaux: Explorer, Collector, Botanist – Explorateur, Collectionneur, Botaniste – North Carolina

As a reminder of his contributions, Reveal gives us the following list of genera Michaux described (reveal also included a list of species) :

  • Anychia Michx., Fl. bor.-amer. 1: 112. 19 Mar 1803.
  • Arundinaria Michx., Fl. bor.-amer. 1: 73. 19 Mar 1803.
  • Botrypus Michx., Fl. bor.-amer. 2: 274. 19 Mar 1803.
  • Brachystemum Michx., Fl. bor.-amer. 2: 5. 19 Mar 1803.
  • Caulophyllum Michx., Fl. bor.-amer. 1: 204. 19 Mar 1803.
  • Centaurella Michx., Fl. bor.-amer. 1: 204. 19 Mar 1803, nom. illeg. (Art. 53.1), non Delarbre (1800).
  • Ceratiola Michx., Fl. bor.-amer. 2: 221. 19 Mar 1803.
  • Crotonopsis Michx., Fl. bor.-amer. 2: 185. 19 Mar 1803.
  • Cteisium Michx., Fl. bor.-amer. 2: 275. 19 Mar 1803.
  • Dichromena Michx., Fl. bor.-amer. 1: 73. 19 Mar 1803, nom. rej. vs. Rhynchospora Vahl (1805).
  • Dilepyrum Michx., Fl. bor.-amer. 1: 40. 19 Mar 1803.
  • Diphylleia Michx., Fl. bor.-amer. 1: 203. 19 Mar 1803.
  • Elodea Michx., Fl. bor.-amer. 1: 20. 19 Mar 1803.
  • Elytraria Michx., Fl. bor.-amer. 1: 8. 19 Mar 1803.
  • Erianthus Michx., Fl. bor.-amer. 1: 54. 19 Mar 1803.
  • Eriogonum Michx., Fl. bor.-amer. 1: 246. 19 Mar 1803.
  • Erythrorhiza Michx., Fl. bor.-amer. 2: 34. 19 Mar 1803, nom illeg. (Art. 52.1).
  • Gonolobus Michx., Fl. bor.-amer. 1: 119. 19 Mar 1803.
  • Helopodium Acharius ex Michx., Fl. bor.-amer. 2: 329. 19 Mar 1803.
  • Hydropeltis Michx., Fl. bor.-amer. 1: 323. 19 Mar 1803.
  • Imbricaria (Schreb.) Acharius ex Michx., Fl. bor.-amer. 2: 322. 19 Mar 1803, nom. illeg. (Art. 53.1), non Comm. ex Juss. (1789).
  • Ipomopsis Michx., Fl. bor.-amer. 1: 141. 19 Mar 1803.
  • Isanthus Michx., Fl. bor.-amer. 2: 3. 19 Mar 1803.
  • Leptanthus Michx., Fl. bor.-amer. 1: 24. 19 Mar 1803.
  • Lespedeza Michx., Fl. bor.-amer. 2: 70. 19 Mar 1803.
  • Melananthera Michx., Fl. bor.-amer. 2: 106. 19 Mar 1803.
  • Micranthemum Michx., Fl. bor.-amer. 1: 10. 19 Mar 1803, nom. cons.
  • Nephrodium Michx., Fl. bor.-amer. 2: 266. 19 Mar 1803.
  • Nolina Michx., Fl. bor.-amer. 1: 207. 19 Mar 1803.
  • Onosmodium Michx., Fl. bor.-amer. 1: 132. 19 Mar 1803.
  • Orchidocarpum Michx., Fl. bor.-amer. 1: 329. 19 Mar 1803.
  • Oryzopsis Michx., Fl. bor.-amer. 1: 51. 19 Mar 1803.
  • Pachysandra Michx., Fl. bor.-amer. 2: 177. 19 Mar 1803.
  • Persoonia Michx., Fl. bor.-amer. 2: 177. 19 Mar 1803, nom. illeg. (Art. 53.1), non Sm. (1798).
  • Petalostemon Michx., Fl. bor.-amer. 2: 48. 19 Mar 1803, as ‘‘Petalostemum,’’ nom. et orth. cons. Physcia (Schreb.)
  • Acharius ex Michx., Fl. bor.-amer. 2: 326. 19 Mar 1803.
  • Pinckneya Michx., Fl. bor.-amer. 1: 103. 19 Mar 1803. Pleea Michx., Fl. bor.-amer. 1: 247. 19 Mar 1803.
  • Podostemum Michx., Fl. bor.-amer. 2: 177. 19 Mar 1803, as ‘‘Podostemon.’’
  • Polygonella Michx., Fl. bor.-amer. 2: 240. 19 Mar 1803.
  • Psoroma Acharius ex Michx., Fl. bor.-amer. 2: 321. 19 Mar 1803.
  • Pycnanthemum Michx., Fl. bor.-amer. 2: 7. 19 Mar 1803, nom. cons.
  • Pyrularia Michx., Fl. bor.-amer. 2: 231. 19 Mar 1803.
  • Pyxidanthera Michx., Fl. bor.-amer. 1: 152. 19 Mar 1803.
  • Schisandra Michx., Fl. bor.-amer. 2: 218. 19 Mar 1803, nom. cons.
  • Scyphophorus Acharius ex Michx., Fl. bor.-amer. 2: 328. 19 Mar 1803, nom. illeg. (Art. 52.1).
  • Setaria Acharius ex Michx., Fl. bor.-amer. 2: 331. 19 Mar 1803, nom. rej.
  • Spergulastrum Michx., Fl. bor.-amer. 1: 275. 19 Mar 1803.
  • Stipulicida Michx., Fl. bor.-amer. 1: 26. 19 Mar 1803.
  • Streptopus Michx., Fl. bor.-amer. 1: 200. 19 Mar 1803.
  • Trachynotia Michx., Fl. bor.-amer. 1: 63. 19 Mar 1803.
  • Trematodon Michx., Fl. bor.-amer. 2: 289. 19 Mar 1803.
  • Trichodium Michx., Fl. bor.-amer. 1: 41. 19 Mar 1803.
  • Tripterella Michx., Fl. bor.-amer. 1: 19. 19 Mar 1803, nom. illeg. (Art. 52.1).
  • Xerophyllum Michx., Fl. bor.-amer. 1: 210. 19 Mar 1803.
  • Zigadenus Michx., Fl. bor.-amer. 1: 213. 19 Mar 1803.

Many thanks to Ruby Roberts (Technical Services) and Kelly Russell (Forest Supervisor) of the National Forest Service for assistance with permission to study and document plants in Apalachicola National Forest.


Reveal, James L., 2005.  ‘No Man is an Island: The Life and Times of André Michaux’  Castanea, Occasional Papers #2.  https://castaneajournal.com/occasional_papers_archives/op_issue_2/26797057_No Man is an Island- The Life and Times of Andre Michaux.pdf

Zomlefer, Wendy B. , Michael McKain, and Jeremy Rentsch, 2014. Documentation of the Chromosome Number for Zigadenus glaberrimus (Liliales: Melanthiaceae) and its Significance in the Taxonomy of Tribe Melanthieae,  Systematic Botany 39(2): pp. 411–414

Zomlefer, Wendy B. and Walter S. Judd, 2002. Resurrection of Segregates of the Polyphyletic Genus Zigadenus s.l. (Liliales: Melanthiaceae) and Resulting New Combinations    NovoN 12: 299-308.

Zomlefer, Wendy B., Walter S. Judd, Mark Whitten, and Norris H. Williams, 2006. A Synopsis of Melanthiaceae (Liliales) with Focus on Character Evolution in Tribe Melanthieae Aliso: A Journal of Systematic and Floristic Botany
Volume 22 Issue 1 Article 44 

Last Updated – 21 August 2023

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