Trillium

 

Common Name: Trillium, wake-robin, trinity flower, white wood lily, birthroot – Trillium is derived from the triplet configuration of its constituent parts concatenated with lilium, the Latin word for lily. The euphonious result is one of the few examples of a  common name that is the genus, a recognition of the latter’s descriptive and mnemonic qualities ― a three-part lily.

Scientific Name: Trillium grandiflora –  The species name of this, the most striking trillium, is Latin for “large-flowered” for its imposing white blossoms. Other notable species are: T. undulatum (undulating) or painted trillium;  T. erectum (erect) or red trillium; T. cernuum (falling headlong) or  nodding trillium; and T. sessile (sitting) or sessile trillium also called toadshade.

Potpourri:  The leitmotif of three that is the hallmark characteristic of trillium flowers is rare among woodland flowers. All is not as it appears, however. The three petals are not petals, the three sepals that form the calyx supporting the flower are not leaves, and the stem that holds them up is not a stem. The entire affair is an extension of the hypogeal rhizome of the rooting system that extends above ground and forms scale-like structures called cataphylls that in most plants are bud scales that precede the formation of foliage. Technically, the trillium is a flowering scape. Thus, the three white “petals” have the same venation as the three green “leaves” and appear as if they were lacking only the green pigmentation of photosynthetic chlorophyll. For all intents and purpose, the “petals” guide pollinators to the center of the flower to collect nectar and spread pollen and the “leaves” carry out the autotrophic function of producing hydrocarbon compounds using the energy of the sun, water, and carbon dioxide. Though unusual in structure, it is standard in form and function. [1]

Spreading  across the forest floor with determined persistence, the rhizome-borne trilliums can take over vast tracts that dominate the understory in spring. They bloom in early spring, usually May depending somewhat on latitude and elevation, about the time that the robins start their annual nesting activities―the common name wake-robin refers to this phenology. A stretch of the Appalachian Trail that extends across the Blue Ridge Mountains in northern Virginia is estimated to have over ten million T. grandiflora that line both sides of the trail and extend out of sight into the woods.  The linear nature of their growth creates a natural monoculture of the same species. The white blossoms fade to pink over the brief weeks of their refulgence, signaling the end of the banquet set for the pollinators to fulfill the reproductive mission. [2]

The biological revolution unfolding in the twenty-first century has nearly demolished the taxonomic structure that has persisted for nearly three centuries. The genetics of clade and phylogeny has supplanted the traditional physiological framework of life. The lily family to which trilliums were originally assigned is a prime example. It was a catchall from the outset, comprised of some five thousand species in 250 genera that were for the most part perennial herbs arising from rhizomes, bulbs or corms (a thickened underground stem section for storing starches), many with showy flowers. [3] While this description is consistent with trilliums, they are no longer included in the lily family, which has been segregated into roughly thirty families that are still under evaluation for final monophyletic (single ancestor) assessment. While there is some discussion of assigning the trillium to their own family, tentatively and logically named Trilliaceae, they are for now assigned to the family Melanthiaceae in the tribe or subfamily Parideae. [4]

The Angiosperm Phylogeny Website (APW) was established in 2001 and has continued as a work in progress through to the present version fourteen to function as an evolving record of the changing plant taxa. One reason for its existence is that books on the subject are out of date as soon as they are published. It is not improbable that this is the future, an ever-evolving understanding of the complexity of life. Just as it is now manifest that every person is the home to millions of resident microbes, the extant microbiome, it is equally true that plants do not live in a vacuum. As one example, most plants rely on the fungi that live and subsist on their roots for key nutrients. This relationship, known as mycorrhizal (fungus root), is what ties a forest together as a single entity in what has been referred to as the wood wide web and which is perhaps more formally now considered the holobiome, something like a macro-microbiome. According to the APW database, the trilliums are in the order Liliales comprised of ten families, 67 genera, and 1,558 species that probably originated in Australia about 30 mya when it was part of the larger Gondwana with Africa, Antarctica, and South America. The individual species of the order are noted for having the largest nuclear genome among the monocots (single cotyledon plants like grasses) … the trilliums are no exception to this. [5]

The vast swatches of the sub-canopy taken over by trillium in some areas is surprising in light of their low fertilization rates and stringent germination requirements. Trillium are known as “self-incompatible” flowers since they cannot fertilize themselves, unlike the perfect flowers that can and do. While this does enhance genetic diversity in mixing genomic contributions, it necessitates the action of third party pollinators, mostly bumblebees and wasps. Field studies have demonstrated that even trillium flowers cross-pollinated by hand only produce fertile ovules two-thirds of the time with some evidence that this is inherent and not pollen limited. [6] The seeds that eventually are produced by at least some of the flowers require almost three months of cold weather to germinate and then an additional year for the first shoots to appear. With ent-like slow growth patience, the herbaceous rhizome grows for about six more years before producing a flower to repeat the cycle.

To offset haphazard fertilization and prolonged growth, the trip from flower to field is expedited by ants, a relationship that goes by the sesquipedalian name myrmecochory. Trillium seeds are elaiosomes (Greek for oil bodies) containing a strophiole with nutrient rich fatty compounds  which occupies about one quarter of the encapsulated volume. This is surely an evolutionary adaptation to attract seed dispersers. Ants have been observed ascending the stem to retrieve the seeds from within the flower but more typically they wait until the seeds drop from the capsule and carry them off to their nests. [7] Ant dispersion thus contributes to trillium spread. A painstaking study over the two year interval 1991 to 1992 radiolabeled seeds from about forty plants and eventually recovered two-thirds of them. All of this to find out that only one fifth were transported more than ten centimeters form the parent plant. [8] This is  not far enough to explain the long range dispersion of trillium, which has been estimated at over one hundred meters a year based on pollen records. While seed movement by wasps has been measured out to thirty meters and by ants as far as seventy meters (according to a 1906 study), a more mobile agent is likely involved. Enter roving bands of voracious white-tailed deer, who browse on Trillium grandiflora to the extent that it is possible to correlate deer density by average plant height. [9] Deer fecal pellets collected from six forest stands near Ithaca, New York confirmed that trillium seeds were indeed present―the site with the highest number was known as Trillium Woods. [10]

There are about forty species of trillium mostly in eastern North America with a few outliers in eastern Eurasia.  They come in two basic types, pedicellate and sessile. The former have flowers attached to a pedicel, which is an extension above the leaves to extend the flower outward, a matter of gaining the attention of pollinators. The trillium pedicel should and sometimes is called a peduncle, which holds an entire flower assembly, as the whole affair is really an outgrowth of a rhizome and not a stem. T. grandiflora is pedicellate as is the nodding trillium T. cernuum as the pedicel is curved downward. This must be to favor a certain type of pollinator. Sessile is then simply “sitting” directly on the leaves with no pedicel or peduncle extension.  The most common example of a sessile trillium is sensibly called the sessile trillium. It is also known as  toadshade for reasons that are not clear other than the pervasiveness of toad as metaphor for the moist areas under forested groundcover, like toadstool. [11]

The alternative common name birthroot refers to the use of some trillium species for medicinal treatments, notably those involving parturition. The most well-known is the red trillium, T. erectum, also pedicellate as the name implies, which contains chemical compounds classified as sapogenins. As with many indigenous plants, the Native Americans had a variety of uses for the red trillium, many of which related to female life cycle issues such as inducing childbirth, treating labor pains and, eventually, menopause. [12] Due to its notoriety as a drug, there are a number of common names that apply only to this species of trillium. Beth root and stinking Benjamin both are derived from benzoin,  a balsamic resin that is extracted from trees  that grow in southeast Asia and used in perfumes, incense, and medicine (there are two types of benzoin  from two different trees leading to some confusion).

Arguably, the most beautiful trillium is the less common painted trillium, which is named T. undulatum for the waviness of its petals. It is an improvement on the basic design  with a starkly contrasting (painted) color-coded guide to direct pollinators to the center of the flower … blithely sweeping past the anthers in pursuit of nectar and unwittingly transferring some pollen to the next plant. The painted trillium was ranked sixth most favored  out of one thousand flowers in a public poll in 1940. [13] If a poll were taken today, trillium flowers would surely rank in the top ten. While they lack the complex shapes and colors of orchids and the floral fragrance of roses, they are the epitome of simplicity and symmetry, uniquely triangular. A trinity lily for spring, and for those so inclined,  Easter Sunday.

 

References:

1. Case, Frederick, “Trillium,” Flora of North America at http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=133668
2. . Stritch, L. “Great White Trillium” at https://www.fs.fed.us/wildflowers/plant-of-the-week/trillium_grandiflorum.shtml
3. 3. Niering, W. and Olmstead, N. National Audubon Society Field Guide to North American Wildflowers, Alfred A. Knopf, New York, 1998 pp 591-617.
4. Utech, Frederick H. “Lily Family,” Flora of North America at http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10507
5. Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 14, July 2017. http://www.mobot.org/MOBOT/Research/APweb/
6. Griffin, S. et al. “Factors Affecting Low Seed: Ovule Ratios in a Spring Woodland Herb, Trillium grandiflorum (Melanthiaceae)”. International Journal of Plant Sciences. July 2002 Volume 163 (4) pp 581–590.
7. Harris, M. Botanica North America, Harper Collins, New York, 2003, pp 108-110.
8. Kalisz, S. et al (1999). “Ant-Mediated Seed Dispersal Alters Pattern of Relatedness in a Population of Trillium grandiflorum” Ecology December 1999, Volume 80 (8) pp 2620–2634
9. Koh, S. et al (2010). “Trillium grandiflorum height is an indicator of white-tailed deer density at local and regional scales” Forest Ecology and Management 31 March 2010 Volume 259 (8) pp 1472–1479
10. Vellend, M. et al. “Dispersal of Trillium Seeds by Deer: Implications for Long-Distance Migration of Forest Herbs” Ecology 2003, Volume 84 (4) pp 1067–1072
11. . https://www.fs.fed.us/wildflowers/beauty/trilliums/about.shtml
12. Foster, S. and Duke, J. Medicinal Plants and Herbs, Houghton Mifflin, Boston, 2000, p 157
13. Sanders, J. Hedgemaids and Fairy Candles, Ragged Mountain Press, Camden, Maine, 1993, pp 54-56