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
The word "dodder" is used in several other interesting ways. Look it up
in an unabridged dictionary.
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Update: June 2012