White Snakeroot seeds are best sown in autumn or spring after cold stratification. This treatment significantly improves germination.
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Native woodland perennial
Asteraceae
Native woodland perennials for pollinators
White Snakeroot (Ageratina altissima) – Seeds
Ageratina altissima
Native partial-shade perennial with airy clusters of late white flowers. White snakeroot brightens woodland gardens and supports bees, butterflies, hoverflies, and other pollinators into early fall.
Quantity
Minimum 75 seeds
Exposure
Light shade to partial shade
Hardiness
Zones 3 to 8
Difficulty level
Moderate
Discover the plant
Family
Asteraceae
Genus
Ageratina
Species
altissima
Cultivar
Type
Native woodland perennial
Cycle
Perennial
White Snakeroot (Ageratina altissima) is a native woodland perennial valued for its airy, luminous white flowers. Upright stems carry dark green, opposite leaves that are broadly oval and strongly toothed. From late summer into early fall, numerous small white flower heads gather in flattened clusters that brighten shaded garden areas. This late bloom period extends seasonal interest after many other perennials have finished flowering. Exceptionally hardy, white snakeroot overwinters reliably in Quebec and gradually forms natural-looking colonies where conditions are suitable. Its dense foliage and fresh white flowers give woodland borders a full, layered appearance without requiring a formal garden setting.
White snakeroot prefers light shade or partial shade in humus-rich, moist, well-drained soil. It tolerates more sun where moisture remains consistent, but foliage may suffer in hot, dry exposure. A mulch of shredded leaves or compost helps keep the root zone cool and recreates the conditions of a natural woodland floor. Water during extended dry periods, especially while plants are becoming established. A light spring application of mature compost is generally sufficient. In Quebec, dry stems may be removed before new spring growth begins or left standing through winter to shelter beneficial insects and provide structure in naturalized plantings.
White snakeroot suits woodland gardens, forest edges, naturalized borders, and pollinator plantings. Its late flowers provide nectar and pollen for bees, butterflies, hoverflies, and many other beneficial insects when fewer floral resources remain available. It pairs naturally with wild columbine, heartleaf foamflower, woodland phlox, and ostrich fern. This native perennial may self-seed and develop colonies under favourable conditions, so unwanted seedlings can be removed when a more contained planting is preferred. All parts are toxic when ingested and the plant should be kept away from livestock, pets, and young children who may chew vegetation.
Planting guide
From planting to establishment.
Planting depth
Surface sow
Spacing / density
45 to 60 cm (18 to 24 in)
Establishment temperature
18 to 22°C
Establishment time
14 to 30 days after at least 60 days of stratification
Best planting time
Spring after the last frost
Propagation
Seed, division, or self-seeding
Growing method
Sow White Snakeroot seeds in autumn or spring after cold stratification to improve germination. Surface sow the seeds, as light promotes successful germination. Keep the growing medium evenly moist at 18 to 22°C (64 to 72°F). Germination generally occurs within 14 to 30 days. Transplant seedlings into humus-rich, well-drained soil in light shade or partial shade. Once established, this native perennial often self-seeds naturally and forms attractive colonies in woodland gardens.
Soil and care
The right conditions.
Exposure
Light shade to partial shade
Soil pH
Acidic to neutral
Hardiness zone
Zones 3 to 8
Minimum temperature
Approximately -40°C
Watering
Moderate; keep soil evenly moist
Soil type
Humus-rich, moist, well-drained soil
Fertilization
Light application of mature compost in spring
Seasonal care
In early spring, remove the previous season’s dry stems before new growth appears, or leave them until the last practical moment to protect overwintering insects. Apply a thin layer of compost or shredded leaves around the plants without covering the crowns. During summer, keep the soil evenly moist and water through extended dry periods. After flowering, retain some seed heads for wildlife and natural reseeding, or remove them to limit spread. Wear gloves when handling the plant, avoid transferring plant material to the mouth, and keep cut stems away from livestock and pets.
Container growing
A controlled environment.
Recommended pot size
30 cm (12 in)
White Snakeroot grows well in containers at least 30 cm (12 in) deep filled with an organic-rich growing medium. Place the container in light shade or partial shade to mimic its natural woodland habitat. Keep the soil evenly moist without becoming waterlogged and apply organic mulch to reduce evaporation. This native perennial creates an attractive woodland display while drawing a wide diversity of pollinators late in the season.
Bloom and dimensions
The complete profile.
Flower color
White
Foliage color
Dark green
Foliage type
Deciduous
Growth rate
Moderate
Bloom period
July to September
Fruiting
Small achenes with white bristles
Maximum height
120 cm
Maximum width
75 cm per plant
Harvest
September to October
Garden associations
What to plant with it.
Good companions
Wild columbine, heartleaf foamflower, woodland phlox, ostrich fern
Avoid planting with
Lavender, cotton lavender, rosemary, and stonecrop
Woodland, forest edge, naturalized border, pollinator garden
From the garden to inspiration.
Frequently asked questions
Everything toknow.
Yes. Its abundant late-summer flowers attract a wide variety of bees, butterflies, hoverflies, and other beneficial pollinators when few other flowers remain.
Yes. White Snakeroot naturally grows in open woodlands and thrives in light shade to partial shade. It also tolerates some direct sun if the soil remains cool and moist.
Absolutely. It is highly recommended for ecological gardens, woodland restoration, and naturalized landscapes where supporting biodiversity is a priority.
Yes. White Snakeroot is fully hardy throughout Canada and returns reliably every year, even after harsh winters.
Its strengths, naturally.
Not recommended for pets
Pets
Attracts or supports pollinating insects
Pollinators
Plants that attract butterflies
Butterflies
Less attractive or generally tolerated by deer
Deer
