Forest Preserve District of Cook County, Illinois
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Nature Bulletin No. 350-A   September 20, 1969
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

In summer and early autumn, here in Illinois, bright yellowish-orange patches appear occasionally among weeds, near marshes, or along moist thickets, which look as if the green vegetation had been scorched by fire. At close range the plants in these places appear to be smothered with tangled masses of coarse yarn. The threads that make up this yarn coil a few times around a leaf or stem and then reach out to strangle another. If we try to unwind one of these treads it breaks before it can be torn loose and its treacherous parasitic habit is exposed.

This is Dodder -- a plant that steals all its food from other plants through suckers that penetrate to their sap channels. Mistletoe, for instance, though it absorbs water and minerals from the host tree, has green leaves to manufacture its own sugar, starch, fiber and wood. But dodder, no honest vine like its relatives, the morning glories, is an example of what eventually happens to a plant, through the ages, when it becomes a parasite: no roots, no leaves, no green chlorophyll to make its own food.

Dodder is called Strangleweed, Love Vine, Angel's Hair and Hairweed. A hundred or more species are scattered over the temperate and warmer parts of the earth. Of the 30 species found in the United States, about nine are widespread. Several, have been introduced from Europe and now we have strict laws against the importing or sale of commercial seeds contaminated with dodder seed.

Most kinds live on a variety of shrubs and non-woody plants but some are parasites only on a certain family of plants or even restricted to a single species. One Illinois dodder, which has unusually large flower clusters arranged in rope-like twists an inch or more thick, attacks wild sunflowers, asters and goldenrod. Another specializes on smartweeds; while a third prefers hazelnut bushes .

The life history of the Common Dodder is typical of these strange plants. In July and August it produces dense clusters of tiny bell-shaped ivory-tinted flowers each about one-tenth of an inch across. These are followed by dry whitish capsules of about the same size, each containing four plump seeds which drop to the ground unless, as occurs in hay fields, they are harvested with the crop. These seeds, which may lie dormant for six or eight years, contain threadlike spirally-coiled embryos that germinate on soil in late spring after other plants have started to grow.

A seed pushes up a yellow thread with a tip that spirals as it seeks a green plant upon which to fasten. If no such victim is found, the young dodder dies within a few days or weeks but, when another plant is touched, the hungry vine coils around it, always in a clockwise direction, and sinks in its rootlike suckers.

As it grows vigorously and throws out fresh suckers, the dodder loses its connection with the ground. Swayed by every breeze, the tendrils branch and constantly reach out for new victims upon which to twist and feed.

The word "dodder" is used in several other interesting ways. Look it up in an unabridged dictionary.

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