Ontario Weeds: Dodder
Excerpt from Publication 505, Ontario Weeds, Order this publication
Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Dodder, twining around a host plant.
Field dodder. Portion of a flowering and fruiting plant tightly twined around a susceptible host. Enlarged segments of the dodder stem indicate where its haustoria have penetrated the tissues of the host.
Stems & Roots: The Dodders are parasitic plants with leafless, thread-like, orange or reddish stems twisting and twining around other plants, often forming dense stringy masses. Being totally without chlorophyll, they must obtain all of their growth requirements (water, minerals, carbohydrates) from other living green plants around which they wind and become attached. Dodder seed germinates in the soil and sends up a slender, thread-like, orange or reddish stem without any cotyledons (seed leaves). This slender stem sways or rotates slowly until it touches the stem or leaf of another plant and begins to wind around it. If this plant is susceptible to attack by Dodder (and many are not) the Dodder stem immediately begins to form haustoria (tiny sucker-like roots). These penetrate the tissues of the host plant and extract all of the Dodder's subsequent growth requirements from it. If the seedling is unable to contact a susceptible plant, it soon withers and dies. Once attached to a susceptible host, the lower end withers and breaks its connection with the ground, while the upper end of the stem grows rapidly, branching and rebranching.
Habitat: Several species of Dodder are native to Ontario, but they occur chiefly in moist or swampy areas where they parasitize native plants. Field dodder, Cuscuta campestris Yunker, [cuscute des champs, cuscute de la vigne], is the most important of these as a parasite on agricultural crops, attacking carrots, petunias, tomatoes, etc.
Similar Species: It is distinguished by its thread-like, yellowish or orange stems that occasionally form masses of tangled threads as they twine and sprawl over other plants. On susceptible plants they curl around the individual stems and produce root-like haustoria that penetrate inside. It is also distinguished by its small, dense clusters of white flowers followed by small, round seedpods.
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