Dodder | Cuscuta spp.

a reflection on a curious plant

By Celestine Urban

During one of our plant walks, Alex led us to walk atop the ridge of an esker. The views were breathtaking. Sunlight streamed in ever-shifting pools through the leaf canopy overhead and the prairie was visible from between the trees. In the distance I noticed strange patches of yellow. I wondered if a controlled burn had happened recently or if the grasses and plants had dried out due to intense sunlight.

In the prairie, dragonflies hovered and the sunlight was hot overhead. When choosing a plant to sit with, I could hardly decide. I felt hot, tired, dry and a little prickly. If there’s anything I’ve learned so far in herbalism, it’s that the right environment can produce the right medicine. Plants in dry places tend to produce mucilage (they hold onto moisture). And so, I headed over to one of the dried yellow patches in search of an ally.

To my horror and dismay, I found that these patches were a tangle of yellow strangling vines. They greedily wrapped themselves around their hosts, blocking out much of their green. They twirled tightly around stalks and leaves and when they ran out of real estate, they wrapped themselves around themselves in some strange act of botanical cannibalism.

I could have chosen another plant at this point, but I was already in too deep.

I felt offended both for myself and for the green plants. I did not find an ally, I found a con artist and a parasite. I had come in search of a friend in some sunburned patch, but alas, I came upon a bright and strange sight.

This plant felt alien. His tendrils grabbed and wrapped themselves around the tall and upright - those who toil in the soil and live honestly by sunlight. He was a soft and juicy vine. Though gentle and easily breakable to human touch, he contained little teeth which sunk into his host. He wrapped and twirled and made a great mess, but he was not satisfied. He produced no leaves. He survived merely on the life of another being.

My heart said he did not make medicine, but I was wrong.

Post-Encounter Research and Reflections

Dodder does make medicine. In Traditional Chinese Medicine (TCM), dodder seeds have an affinity for the kidneys and liver channels and are considered a tonic herb for yang deficiency. Dodder seeds are acrid, sweet and slightly warming in nature. The Western Herbalism analogues to these properties would be acrid, sweet, warming in the first degree and diuretic. They bind up what is relaxed/leaking fluids, they nourish, dry and stimulate.

Dodder’s seeds can lay dormant beneath the soil for about 10 years (some sources say 20 years, some 5-7 years). Once the seeds sprout, the seedling must find a host. If it does not find a host within 5-10 days (reaching a height of 1 ft), it will die. If it does find a host, it will insert haustoria (modified adventitious roots) into its host plant’s vascular system and tap the water, minerals and nutrients. After this, its connection to the soil ends. Although dodder is weakly photosynthetic, it will survive primarily off of the host over the course of its life. Come early fall, it produces copious amounts of flowers and seed.

Dodder is classified as a parasitic plant because of its haustorium. However, thinking back to my encounter with dodder in the prairie, the patches of host plants it chose were well established, tall and strong. Dodder did not grow among low lying plants, on those which stood lonely nor did it choose weak plants. Rather, it seemed to seek out those which were threatening to take over and weaved itself around them to rein them in. While it may be a parasite to the individual, it’s not a parasite to an ecosystem and the native species in particular may help increase biodiversity.

Also, while dodder takes up nutrients from its host plant, it’s not a one way exchange. It also carries viruses, mRNA, proteins and other macromolecules from one host to another, across species, between taxonomically disparate groups. If one species in an ecosystem is lacking nitrogen, mRNA carried across the network of dodder can signal other species to begin taking up more nitrogen. Some plant viruses may also help confer tolerance to harsh environmental conditions. And if one plant in a system is being damaged by insect feeding, the dodder network carries signals to other plants to produce chemicals to defend themselves. Thus, dodder can increase nutrient cycling, help facilitate interactions between species and encourage resilience.

Dodder is present throughout the world and there are species native to almost every wetland, coastal plain marsh, sandy lake margin, mud flat and agricultural field worldwide. It favors moist and disturbed environments. Smartweed Dodder or Cuscuta polygonorum is considered native to Illinois.

References:

Bensky, D., Gamble, A., Clavey, S., Stöger, E., & Bensky, L. L. (2015). Cuscutae Semen. In Chinese herbal medicine (pp. 802–804). essay, Eastland Press.

Bouwmeester, H., Sinha, N., & Scholes, J. (2021, April 23). Parasitic plants: physiology, development, signaling, and ecosystem interactions. Plant physiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8133663/

Hettenhausen, C., Li, J., Zhuang, H., Sun, H., Xu, Y., Qi, J., Zhang, J., Lei, Y., Qin, Y., Sun, G., Wang, L., Baldwin, I. T., & Wu, J. (2017). Stem parasitic plant Cuscuta australis (dodder) transfers herbivory-induced signals among plants. Proceedings of the National Academy of Sciences, 114(32). https://doi.org/10.1073/pnas.1704536114

Hoyt, C. (2020, September 25). What Does the Dodder Say?. National Parks Service. https://www.nps.gov/bibe/learn/nature/dodder-story.htm#:~:text=According%20to%20Dr.,out%20the%20shy%2C%20retiring%20types.

Mueller, M. (2019, May 23). Did You Know? That Orange Leafless Plant on the Prairie is Rope Dodder. Forest Preserves of Cook County. https://fpdcc.com/rope-dodder-prairie-parasitic/#:~:text=This%20particular%20species%20of%20dodder,robust%20plants%20in%20the%20prairie.

Roossinck, M. J. (2015, May). A new look at plant viruses and their potential beneficial roles in crops. Molecular plant pathology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6638535/

Science Direct (Ed.). (2008). Parasitic Plant. Parasitic Plant - an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/parasitic-plant

Těšitel, J., Li, A.-R., Knotková, K., McLellan, R., Bandaranayake, P. C. G., & Watson, D. M. (2021, April 23). The bright side of parasitic plants: what are they good for?. Plant physiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8133642/#:~:text=Many%20parasitic%20plants%20enhance%20nutrient,medicinal%20and%20cultural%20purposes%20worldwide.

University of Wisconsin-Madison. (n.d.). Dodder, Cuscuta spp. Wisconsin Horticulture. https://hort.extension.wisc.edu/articles/dodder-cuscuta-spp/