If there was a prize for “plant most resembling silly string,” dodder would win. This unusual, vining plant has the appearance of a decorative afterthought, strewn along the tops of plants at random. Dodder is a parasitic plant, with over a hundred varieties growing worldwide. Given lots of harrowing nicknames—hellbine, devil’s guts, witches’ hair, wizard’s net, fireweed, scaldweed, and strangle weed—the plant clearly freaks people out. That wariness may be warranted, as recent research shows that dodder seedlings use a chemical sensory mechanism to detect gases emitted by potential plant hosts. To put it in more human terms, baby dodder plants can “smell” a proper plant host nearby, and start creeping that direction so they can attach and feed on it. Even the botanists who study it are a bit unnerved at how animal-like the plant seems. Dodders also have RNA functions that shut down host plant defenses, allowing free flow of nutrients from the plant directly to the parasitic dodder.
Dodder vines atop a saltbush shrub in the dunes at Perdido Key. Photo credit: Carrie Stevenson, UF IFAS Extension
Dodder is a leafless plant that stays a muted gold/yellow because it does not produce enough chlorophyll to turn green. It takes its water and nutrients from host plants via modified peg-like roots called “haustoria.” Relying completely on the host plant, mature dodder plants let go of their soil-bound roots and reattach fully to the host.
The bell-shaped dodder flowers are produced this time of year (late summer/early fall) and emerge in clusters. The round seeds are quite small (1/16”) and can lie dormant—but viable—for over ten years in the soil.
For my fellow plant nerds out there, dodder is in the genus Cuscuta, and was long considered the only member of the Cuscutaceae family. However, it has more recently been placed in the family with morning glory vines (Convolvulaceae).
I typically see small dodder vines on coastal dunes or on woody shrubs in open natural areas further inland. Despite its parasitic nature, dodder is not a huge problem locally. It can, however, be a major nuisance in clover, soybean, and tomato crops. To manage dodder infestations, both the dodder and the plants it is hosting upon should be removed before seed production. To prevent spread, equipment used in an area with dodder should be cleaned before taking to another location.
Like many plants, dodder is being researched for its pharmaceutical benefits. In an article reviewing the medicinal properties of the plant, the authors noted “More than half of the clinically approved drugs in the world are either natural products or their modifications.” Long in use in traditional Indian and Chinese medicine for everything from tumors and ulcers to high blood pressure and migraines, modern studies show huge pharmacological promise due to anti-inflammatory, antiviral, anti-ulcer, and cancer prevention properties. While showing great potential for medicinal uses, never use a product like this without first consulting a medical professional.
Dodder overtaking a tree in Pakistan. Source: Wikipedia commons
There are many problems that can plague a plant in our environment, from fungi that love the humidity in North Florida to insects that chew through leaves. One less common but interesting source of stress for plants comes from…other plants?
Most plants are content to gather energy from sunlight and nutrients from the soil in which they sink their roots. Some species, however, have taken up thievery as a lifestyle. Parasitic plants are those that take the nutrients they need to grow from other plants. Some rely completely on their hosts for nutrients, others are able to produce at least some of their own, while yet more can live on their own but steal nutrients if another plant is conveniently nearby. Furthermore, there are some plants and similar organisms that may seem to be parasitic, but actually do no harm.
Mistletoe is a common sight especially in the winter when trees’ leaves have dropped. It relies on its host for water and nutrients, though it can produce energy from photosynthesis. Being evergreen has led it its adoption as a symbol Christmastime, and it has historically been important to other cultures such as the Celtic druids. Too much mistletoe can weaken a tree, and removing it can help to reinvigorate one that is struggling. Physical pruning is often the only method available for its removal, and this can be difficult on a tree of any size.
Yellow tendrils and white flowers of dodder.
Dodder has a strange appearance, looking like someone threw a batch of angel-hair pasta all over a plant. There are ten different species of dodder in Florida and they may be found on a variety of host plants. This parasite is leafless and takes all it needs from its host, and cannot survive independently; though it germinates from the ground, it has no true roots. Controlling an infestation of dodder involves removing affected plants or at least pruning off the branches that are hosting the parasite. Herbicides will kill it, but they will also kill the host.
Ghost Pipe flowers
Ghost Pipe may be seen flowering from early summer through autumn, typically in woodland areas. It does not take its nutrients directly from a tree, but instead from mycorrhizal fungi. These helpful fungi attach to a tree and act like extra roots, assisting to absorb nutrients in return for energy from the plant. The ghost pipe helps itself to both nutrients and energy and does not bother to photosynthesize for itself, which gives it its stark white appearance.
Lichen may grow profusely on trees, but does not harm the plant.
There are also plenty of harmless plants out there, such as Spanish moss and resurrection fern, which grow on trees but are not parasitic. Lichens, while not plants, are similarly prolific on the bark of trees, but do no harm.
For help in identifying a potential parasitic plant, contact your local Extension office.
