Is white snakeroot invasive?

It can be aggressive in garden settings due to its prolific seed production and rhizomatous spread.

Does it need full sun?

It prefers partial shade but will tolerate full sun if the soil remains consistently moist.

Plant guide

White Snakeroot.

Ageratina altissima

Pronounced ah-jer-ah-TEE-nah al-TISS-ih-mah

Also known as Richweed, Snakeroot, White Sanicle, White Snakeroot, White Snakeroot

White snakeroot is a hardy perennial native to North America that produces clusters of fuzzy white flowers in late summer. It is a woodland plant that spreads easily through rhizomes and seeds. You will find it thrives in shaded areas with consistent moisture.

Another photo of White Snakeroot — Photo by Jonathan Sowers (CC0) via gbif

At a glance

Care level: Easy
Plant type: Perennial
Light: Partial shade to full shade
Indoor light: Medium light
Water: Every 3 to 7 days
Mature size: 5 feet
Growth rate: Fast
Hardiness: USDA 3 to 8
Bloom time: Late summer to mid autumn

Care

Keep the soil consistently moist to mimic its natural woodland habitat. Watch for wilting during dry spells, as this plant does not tolerate drought well. It can become aggressive in garden settings, so keep an eye on its spread.

Watering: Water whenever the top inch of soil feels dry to the touch.
Feeding: A light application of compost in early spring is usually plenty.
Pruning: Cut the plant back to the ground in late winter or early spring.
Repotting: If grown in a container, move to a larger pot once the roots fill the current space.
Soil: Rich, moist, well draining soil
Soil pH: 6.0 to 7.5
Temperature: -40 to 35°C
Humidity: 40 to 70%

Safety

People: All parts of the plant are highly toxic to humans and animals.
Pets: This plant is toxic to cats and dogs if ingested.
Children: Keep this plant away from children as all parts are poisonous if eaten.
Contact allergens: Handling the foliage may cause mild skin irritation in sensitive individuals.
Airborne allergens: The pollen can cause allergic reactions in some people during the late summer flowering period.
Edibility: This plant is toxic if ingested and should never be consumed by humans or livestock.

How to identify it

Opposite, serrated, heart shaped leaves
Clusters of small white flower heads
Stems are smooth and often purple tinted
Mature height reaches 3 to 5 feet

Height: 0.9 to 1.5m
Spread: 0.6 to 0.9m
Leaves: dark green, deciduous
Flowers: white, 0.5 to 1cm

Problems to watch for

Powdery MildewCommon
AphidsUncommon
Leaf SpotUncommon
RustUncommon
Slugs and SnailsUncommon
Root RotRare

By symptom

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Growing it

Propagation: division, seed
When to plant: spring, autumn

Pair this plant with other late blooming perennials to ensure a continuous food supply for pollinators until the first frost.

Grows well with

Goldenrod · They bloom at the same time and create a beautiful contrast of white and yellow.
New England Aster · This aster provides a lovely purple companion to the white snakeroot flowers.

Similar species

Boneset · It has similar white flower clusters but prefers much wetter soil conditions.

Science

Family: Asteraceae
Genus: Ageratina
Order: Asterales
Class: Magnoliopsida
Native range: Eastern and central North America.
Conservation: This plant is common and secure throughout its native range.

It naturally colonizes forest edges and clearings where it provides essential late season nectar for insects.

Value to wildlife: late season nectar source, supports diverse pollinators
Pollinators: bees, butterflies, moths
Uses: pollinator gardens, woodland borders, naturalized areas

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 1/9
Soil reaction: 5/9
Light: 5/9
Temperature: 5/9
Moisture: 6/9
Nutrients: 5/9

Taxonomy resolved against GBIF.

Questions people ask

Is white snakeroot invasive?: It can be aggressive in garden settings due to its prolific seed production and rhizomatous spread.
Does it need full sun?: It prefers partial shade but will tolerate full sun if the soil remains consistently moist.

Where the name comes from

The genus name Ageratina comes from the Greek word for ageratos, meaning not aging, while the species name altissima means very tall.

Good to know

It is commonly known as white snakeroot.
The plant was responsible for the death of Abraham Lincoln's mother, Nancy Hanks Lincoln.
It thrives in the dappled shade of deciduous forests.
The flowers appear as fluffy white clusters that brighten up autumn gardens.

Also in

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This guide was generated with AI on September 26, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.