Dodder is an annual parasitic weed that grows only by penetrating tissues of host plants to obtain water and nutrients. It is found throughout California up to an elevation of 8200 feet (2500 m). Species native to California usually grow on various herbs and shrubs in most natural communities and are not considered weeds in these conditions. However, some dodder species are problematic in agricultural fields, especially alfalfa, clovers, and tomatoes. Occasionally, dodder inhabits nursery crops and landscaped sites. Although the host plant range is large, it seldom affects monocots, except for onions and asparagus. The distinctive orange, red, or yellow twining dodder shoots are unlikely to be confused with any other plant. Species identification is difficult.
Seedling
Dodder seedlings lack cotyledons (seed leaves) and develop a small temporary root to support a roughly 1-1/2 to 4 inch (4–10 cm) threadlike, yellow, orange, or red shoot. Depending on the species, seedlings have from about 10 days to several weeks to attach to a suitable host; otherwise they die.
Mature Plant
Threadlike, hairless, yellow, orange, or red shoots twine around host plants eventually creating a tangled mat. Knoblike organs along the shoot (haustoria) penetrate the host stem. Shoots either lack leaves or have very tiny red, yellow, or orange scalelike leaves pressed close to the stem. Dodder lacks the usual underground roots of other plants. Once it attaches to the host, the soil connections dry up and die.
Flowers
Flowers bloom generally from May through October. The tiny flower petals are less than 1/4 of an inch (6 mm) long, bell-shaped, and occur in inconspicuous clusters.
Fruits
Fruits consist of spherical, egg-shaped, or conical capsules that are mostly less than 1/5 of an inch (5 mm) in length.
Seeds
Each plant produces thousands of seeds that can remain dormant in the soil for years. There are one to four seeds per capsule. Seeds are tiny, hard, spherical, oblong, egg shaped, or angular and about 1/12 of an inch (2 mm) or less in diameter.
Reproduction
Reproduces from seed and from stems.
