Rare Species Guide

  Basis for Listing

Arisaema dracontium (green dragon) is found in active floodplain forests dominated by Populus deltoides (cottonwood) and Acer saccharinum (silver maple). Therefore in Minnesota, it occurs only in the southeastern corner of the state (Eastern Broadleaf Forest Province). Recently completed surveys in this region have discovered very few occurrences of A. dracontium. Furthermore, those occurrences that have been found are usually small, contain few individuals, and are restricted to remnant floodplain habitats. Floodplain habitats are sometimes considered safe from development because periodic flooding makes them unsuitable for housing, road building, commerce, and most forms of agriculture. That said, floodplain habitats are still succumbing to the direct and indirect effects of a variety of development schemes. Disturbance associated with the loss of tree canopy cover results in the spread of destructive non-native grass species that quickly invade and displace native flora. Given the species restrictive habitat requirements and limited geographic range in the state, the historic loss and degradation of floodplain forest habitats, the current threats posed by land use changes and invasive species, and the burgeoning human population that is fueling an intense competition for land, Arisaema dracontium was listed as a species of special concern in 2013.

  Description

Species in the family Araceae are often called “aroids”, and are characterized by an inflorescence that consists of a spathe and spadix. There are only four native aroids in Minnesota and two in the genus Arisaema; these are A. triphyllum (jack-in-the-pulpit) and A. dracontium (green dragon). Except for the shape of the leaves, A. dracontium is similar to the common and familiar A. triphyllum. The major difference is that the single leaf of A. dracontium consists of 7-13 spirally arranged leaflets, and the leaf of A. triphyllum has just 3 leaflets. Also, the spadix (the structure that bears the flowers and fruit) of A. dracontium is long and slender, and is much longer than the spathe (the leaf-like structure in the inflorescence). By comparison, the spadix of A. triphyllum is much shorter and is covered by the larger spathe. Arisaema dracontium produces tight clusters of fleshy red berries; each berry is 7-13 mm (0.28-0.40 in.) long and contains 1 or 2 seeds (Thompson 2000).

  Habitat

In Minnesota, A. dracontium was originally thought to be restricted to the floodplain forests along the Mississippi River and its major tributaries in southeastern Minnesota. However, surveys in 2009 and 2010 of south central Minnesota revealed occurrences of the plant on other rivers including the Cedar and the Blue Earth.  Additional plants were discovered in wet forests along small streams and creeks that feed into these larger rivers as well. In the larger floodplain forests, plants are often found under canopies of Acer saccharinum (silver maple) and Populus deltoides (cottonwood). In wet forest habitats where this species occurs, the typical canopy trees include Ulmus americana (American elm), U. rubra (red elm), Fraxinus pensylvanica (green ash), Juglans nigra (black walnut), and Tilia americana (basswood). Common associated species in both habitats include Laportea canadensis (wood nettle) and Arisaema triphyllum (jack-in-the-pulpit).

  Biology / Life History

Several curious aspects of this plant’s life history deserve discussion, with perhaps the most curious being the ability of A. dracontium to switch gender from year to year. When plants are small, they produce only male flowers; but in successive years, when the same plant becomes larger, it produces both male and female flowers simultaneously. Furthermore, the larger a plant becomes, the more female flowers and fewer male flowers it produces. Very large individuals may become entirely female (Clay 1993). This phenomenon is related more to the physical size than to the age of the plant, though size generally increases with age. Another notable feature of A. dracontium is its ability to survive in flood-prone habitats. In fact, at least in Minnesota, A. dracontium appears to be entirely restricted to habitats that regularly flood in the spring. And finally, this species is also able to complete its entire life cycle in continual shade.

Arisaema dracontium produces neither perennial rhizomes nor tubers; instead, each plant overwinters as a corm, and limited clonal growth occurs via cormlets budding from the parent corm. Seed production does occur, though seedlings are reported to be uncommon; and a cold and wet period (such as winter in Minnesota) greatly enhances seed germination (Yang et al. 1999). It has also been reported that A. dracontium is self-incompatible, meaning that cross-pollination is needed in order to produce viable seeds (Boles et al. 1999); cross-pollination is insect-mediated. Given the fleshy and brightly colored nature of the fruit, it can be inferred that dispersion of the seeds is likely accomplished by frugivorous animals. Dispersion of corms may result as a consequence of flooding.

  Conservation / Management

In Minnesota, A. dracontium occurs only in mature hardwood forests that develop on active floodplains (floodplain forests and wet forests) in the southeast portion of the state (Eastern Broadleaf Forest Province). This degree of specialization must be taken into account when formulating management plans. Any such habitat that is deprived of its normal flood regime (for example through dam or dike building or diversions) can be expected to deteriorate. Maintenance of the forest canopy is also essential. Experience has shown that logging on floodplains creates opportunities for Phalaris arundinacea (reed-canary grass), a destructive European species that quickly invades and dominates damaged floodplain habitats.

  Best Time to Search

Since A. dracontium can be seen and recognized at any time during its growing season, searches can be conducted from around May 10 to around September 8. In some habitats, the easiest time to see A. dracontium is in late spring, before the wood nettle (Laportea canadensis) fully develops.

  Authors/Revisions

Welby R. Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Boles, R. L., J. Lovett-Doust, and L. Lovett-Doust. 1999. Population genetic structure in green dragon (Arisaema dracontium, Araceae). Canadian Journal of Botany 77(10):1401-1410.

Clay, K. 1993. Size-dependent gender change in green dragon (Arisaema dracontium, Araceae). American Journal of Botany 80(7):769-777.

Marinelli, J., and J. M. Randall, editors. 1996. Invasive plants: weeds of the global garden. Brooklyn Botanic Garden, Brooklyn, New York. 111 pp.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.

Minnesota Department of Natural Resources. 2006. Tomorrow's habitat for the wild and rare: An action plan for Minnesota wildlife, comprehensive wildlife conservation strategy. Division of Ecological Services, Minnesota Department of Natural Resources. 297 pp. + appendices.

Thompson, S. A. 2000. Araceae. Pages 128-142 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 22. Oxford University Press, New York, New York.

Yang, J., J. Lovett-Doust, and L. Lovett-Doust. 1999. Seed germination patterns in green dragon (Arisaema dracontium, Araceae). American Journal of Botany 86(8):1160-1167.