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Cuscuta spp.

dodders

Convolvulaceae

Worldwide, mainly warm temperate Americas

Attracts Pollinators

Native to North America

SunFull Sun – Part Shade

WaterLow

HardinessZones 3–11

Overview

Cuscuta spp. is a genus of roughly 100 to 200 species of parasitic plants in the morning-glory family (Convolvulaceae), found on every inhabited continent. The plants consist of slender, twining, thread-like stems in yellow, orange, or red, almost wholly without leaves, which are reduced to tiny scales, and with little or no chlorophyll. After a seedling germinates and makes brief contact with the ground, it attaches to a host plant and forms peg-like organs called haustoria that penetrate the host stem to draw water and nutrients; the dodder's own root then dies, leaving it entirely dependent on the host. The stems wind and branch over their hosts in dense, tangled mats, producing clusters of small white, cream, pink, or yellow bell- or cup-shaped flowers 0.1-0.2 inch (2-5 mm) across through summer and autumn. Seeds are produced in large numbers and can remain viable in soil for years. Many species are serious agricultural weeds of alfalfa, clover, flax, and other crops, and some are regulated to limit their spread. The common names dodder, strangleweed, and witch's hair describe the twining, smothering growth. The genus has no soil roots and no functional leaves once established.

Native Range

Cuscuta spp. species occur worldwide, with the greatest diversity in warm temperate and subtropical regions of the Americas. Various species are native across North and South America, Europe, Asia, and Africa, and several have spread far beyond their original ranges through contaminated crop seed.

Suggested Uses

Cuscuta spp. has no ornamental garden use and is managed as a weed wherever it appears. A few species, such as C. chinensis, are gathered for use in traditional Asian medicine. In natural habitats it acts as a native parasite that can shift the balance among host plant species.

How to Identify

Unmistakable as leafless, rootless tangles of thin yellow, orange, or red stems twining tightly over other plants, with no green coloring of its own. Small scale-like points replace the leaves, and dense clusters of tiny pale flowers appear along the stems in summer. The threads wrap counterclockwise and attach to hosts by small swellings (haustoria) where they touch. The lack of leaves, roots, and chlorophyll separates Cuscuta spp. from all non-parasitic vines.

Appearance

Size & Dimensions

Height6" - 3'

Width/Spread1' - 5'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~16 weeks

Summer Fall

Cuscuta spp. flowers from summer into autumn, generally June to October, producing dense clusters of tiny white to pale yellow or pink flowers along the twining stems. Each plant can set very large quantities of seed over the season. Flowering follows several weeks after the seedling has attached to a host.

Detailed Descriptions

Flower Description

white, cream, pink, or yellow

Foliage Description

leafless (scale-like)

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 8.0(Neutral)

357912

Soil Types

loam clay sand

Drainageaverage

Water & Climate

Water Needs

Low

Frost Tolerance

tender

Time to Maturity

annual; flowers within weeks of attaching

Care & Maintenance

Care Guide

Cuscuta spp. is a parasite and is not cultivated; it grows wherever suitable host plants and warm conditions occur. A seedling has only a few days to reach a host before its small seed reserves run out, after which it survives entirely on the host's sap. The plants favor open, sunny sites with dense host vegetation, such as crop fields, field margins, and wetlands. Because they drain water and nutrients from their hosts, heavy infestations weaken and can kill crops and ornamental plants. Control relies on using clean seed, removing and destroying infested host plants before the dodder sets seed, and breaking the cycle of viable soil seed over several years. The seeds can stay dormant in soil for up to several years.

Pruning

Cuscuta spp. is not pruned as an ornamental. Where it appears as a weed, the infested portions of the host plant are cut out and destroyed before the dodder flowers and sets seed, since fragments of stem can re-attach and continue growing. Repeated removal over several seasons is needed to exhaust the soil seed bank.