As much as I love the color orange, when I see stringy orange masses along the roadways, I am not happy.
The vine in question is dodder, an annual parasitic vine related to morning glory. Its thin, thread-like, yellow or orange stems grow rapidly entwining and covering their host plants. Dodder is a weird plant. It grows from a seed in the spring, and has 5-10 days to find its target—a host plant. If it doesn’t find a plant to grow on, it dies. If it does find a host, it immediately sets up house—wrapping itself around the stems and then inserting a sucker-like attachment called haustoria, which it uses to take nourishment from the host plant. Once it finds a home, it severs any attachment to the soil, so has no roots.
The plants have very little chlorophyll on their own so they can’t manufacture any food, relying on the host plant to supply it. Usually the vines are yellow or orange, getting more pronounced with color as they grow and form a tangled mass.
In late summer and early fall, they bloom with tiny white bell-shaped flowers. After blooming, they set small rounded fruits or seed capsules the same color as the stems that contain 2-3 seeds. Dodder is a prolific seed producer; a single plant can produce thousands of seeds. The plant is an annual, so is killed after a frost, but the seeds will remain to grow again next year. Dodder seeds are spread primarily through the movement of soil and equipment by humans, or in infested plant material.
Dodder is not commonly found in gardens or ornamental landscapes, but if you see it, it should be removed immediately as dodder is difficult to control once introduced.
I have seen it in azaleas, chrysanthemums and other ornamentals. Once attached to a host plant, complete eradication from the host plant is usually not possible as dodder can grow back from haustoria embedded in the plant. Pruning is of little benefit unless only one or two branches are affected and can be removed without destroying or disfiguring the entire plant. If the plant can be pruned significantly lower than the dodder you have a chance of control, but usually it is best to remove the entire host plant to eradicate the dodder.
If the dodder plants have already set seed, burn them (if allowed locally) or dispose of them in the trash. In areas that have been infested previously, the area should be monitored closely for the presence of seedlings and pull them as soon as they are seen or the soil can be treated with a preemergent herbicide before seeds germinate in spring.
Common names for dodder are love vine, devil’s hair, goldthread, strangle weed, witch’s hair, hellweed and many others. Regardless of what it is called, you don’t want it.