Excerpts from Jim Conrad's
Naturalist Newsletter

Big-seeded Dodder, CUSCUTA INDECORA

from the December 9, 2012 Newsletter issued from the valley of the Dry Frio River in northern Uvalde County, southwestern Texas, on the southern border of the Edwards Plateau, USA
DODDER FLOWERING

Another plant still flowering so late in the season, and doing so quite lustily, is the one shown above. In that picture the flowers are the white things enmeshed among the orangish threadlike stems growing over dead or almost dead weeds. You may recognize this as a parasitic plant that goes by lots of names. I've always called it dodder, but other people might call it angel's hair, devilguts, devil's hair, devil's ringlet, goldthread, hailplant, hairweed, hell bind, love vine, pull down, stranglevine, strangleweed, tangle gut, witches' shoelaces, scald or other such name.

Basically dodder is a plant closely related to the morning-glories that wraps its stems around a host plant, sending rootlike projections called haustoria into the host's tissue, and stealing nourishment from the host. Since dodder is completely parasitic it doesn't need chlorophyll for photosynthesis, or even leaves to serve as solar collectors, so dodder consists of nothing but stems, haustoria, and flowers and fruits. Below, in a picture made through a dissecting scope, you can see an orange dodder stem twining around a host stem, with elephant-foot-like projections from which smaller haustoria arise and enter the stem:

Big-seeded Dodder, CUSCUTA INDECORA, where haustoria enter host stem

A cluster of our dodder's 1/16th-inch tall (2mm) flowers is shown below:

Big-seeded Dodder, CUSCUTA INDECORA, flowers shown from above

A side view of other flowers appears below:

Big-seeded Dodder, CUSCUTA INDECORA, flowers side view

That last picture shows some important field marks for distinguishing which species this is. Though it's easy to see that a dodder is a dodder, identifying dodders to species level can be hard. The Flora of North Central Texas lists ten species for that area, and I figure we have about that many here. Among identification features important to notice in the last picture are:

This dodder keys out as CUSCUTA INDECORA, sometimes called Big-seeded Dodder and other names. Some dodder species parasitize just a narrow range of host plants but Cuscuta indecora is known for attacking a wide variety of species.

Normally dodder populations are so small that they don't seriously alter the local ecology. They may weaken and cause the early deaths of individual host plants, though, and in some crops, such as Alfalfa, dodder can cause serious loss of production.