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Conopholis americana

American cancer-root

Orobanchaceae Eastern North America

Attracts Pollinators

Native to North America

SunFull Shade

HardinessZones 3–9

Overview

Conopholis americana is a non-photosynthetic perennial that parasitizes the roots of oaks, drawing all its water and nutrients from the host through a swollen underground tubercle. It lacks chlorophyll and produces no green leaves. Above ground it appears as clustered, yellowish-brown to tan spikes 3-8 inches (8-20 cm) tall, each densely covered in overlapping scale-like bracts that give the look of a pinecone or ear of corn. Small tubular flowers, pale yellow and two-lipped, open between the scales from spring into early summer. The spikes darken to brown and turn woody as they age, persisting through the season after the flowers fade. The plant forms dense clumps where a host root system is colonized, often reappearing in the same spot for years as the underground structure enlarges. Seeds are minute and dust-like, dispersed near the parent and germinating only in response to chemical signals from a suitable oak root. C. americana grows in mature deciduous and mixed forests with established oaks, in leaf-littered, shaded soil. It cannot be transplanted or cultivated apart from its host and is rarely seen outside intact woodland. Bears and deer feed on the fleshy spikes, an association reflected in the name bear corn.

Native Range

Conopholis americana is native to eastern North America, from Nova Scotia and Ontario south to Florida and west to Wisconsin and Texas, wherever oak forests occur. It grows in the leaf litter of mature deciduous and mixed woodland.

Suggested Uses

C. americana is not a garden plant and is not sold in the nursery trade. It is encountered in natural oak woodland and is of interest in native-plant study and woodland ecology. Intact forest with mature oaks is needed for it to occur.

How to Identify

Recognize C. americana by its clustered, leafless spikes of yellowish-brown overlapping scales, 3-8 inches (8-20 cm) tall, emerging directly from the forest floor near oak trunks. The form resembles a pinecone or ear of corn. Small two-lipped yellowish flowers sit between the scales in spring. The plant has no green tissue at any stage.

Appearance

Size & Dimensions

Height3" - 8"

Width/Spread3" - 6"

Colors

Flower Colors

yellow

Foliage Colors

brown

Bloom Information

Bloom Period

~6 weeks

Spring

C. americana flowers from April to June, soon after the spikes emerge. The small tubular flowers open in sequence along each spike, pollinated by bees and other insects. By midsummer the spikes turn brown and woody and shed dust-like seeds.

Detailed Descriptions

Foliage Description

none; yellowish-brown scales

Growing Conditions

Sun Requirements

SunFull Shade

Tolerates up to 2 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 Range5.0 - 7.0(Neutral)

357912

Soil Types

loam

Drainagemoist

Water & Climate

Frost Tolerance

hardy

Time to Maturity

3-5 years

Care & Maintenance

Care Guide

C. americana cannot be grown in ordinary cultivation because it depends entirely on living oak roots for survival. It establishes only in mature forest soil where compatible host trees and the right fungal and chemical conditions exist. The plant tolerates deep shade and undisturbed, leaf-littered ground. It takes everything from the host and gathers no water or nutrients on its own. Disturbance of the host roots or soil typically destroys the colony. No feeding, watering, or pruning applies to a parasitic plant of this kind.

Pruning

C. americana is not pruned. The brown, woody spikes can be left to disperse seed and decay in place. Removing them has no effect on the underground parasitic structure, which persists on the host root.