Silver Bur Ragweed

(Ambrosia chamissonis)

Silver Bur Ragweed (Ambrosia chamissonis)

Larry Blakely

Public Domain

Image By: Larry Blakely

Recorded By:

Estimated Native Range

Summary

Ambrosia chamissonis, commonly known as Silver Bur Ragweed, is an evergreen perennial subshrub native to coastal dunes and bluffs along the Pacific Coast of North America, from California to British Columbia, and Central Chile. It typically forms a dense mat up to 3 meters (9.8 ft) wide. The stems are covered with soft to rough hairs and have longitudinal ridges. The leaves are woolly, silver-green, and variable in shape, usually a few centimeters long, contributing to the plant’s silvery appearance. Silver Bur Ragweed is monoecious, with both male and female flowers on the same plant. The male flower heads are pale and located at the tips of the inflorescence, while the female flower heads are clustered below, each containing a single flower that matures into a spiny, brown bur up to a centimeter wide.

This plant is valued for its ability to stabilize sandy soils with its extensive root system, making it useful for erosion control on coastal sites. It is also appreciated for its drought tolerance and the unique silver-green foliage that adds contrast in naturalistic plantings. Silver Bur Ragweed thrives in full sun and can tolerate a range of water conditions, from low to medium, but requires well-drained soils. It is not commonly used in formal garden settings due to its aggressive spreading nature and the potential for the burs to become a nuisance. Gardeners should be aware that it can cause allergic reactions similar to other ragweeds.CC BY-SA 4.0

Plant Description

Plant Type: Subshrub, Herb, Shrub
Height: 2-3 feet
Width: 4-5 feet
Growth Rate: Moderate
Flower Color: Yellow, Green
Flowering Season: Fall, Summer
Leaf Retention: Evergreen

Growth Requirements

Sun: Full Sun
Water: Low, Medium
Drainage: Fast, Medium

Common Uses

Bird Garden, Butterfly Garden, Erosion Control, Low Maintenance

Natural Habitat

native to coastal dunes and bluffs along the Pacific Coast of North America, from California to British Columbia, and Central Chile

Other Names

Common Names: Beachbur, Silver Burr Ragweed, Silver Beachweed, Silver Burrweed, Herbe À Poux De Chamisso

Scientific Names: , Ambrosia chamissonis, Franseria chamissonis, Ambrosia chamissonis var. chamissonis, Ambrosia chamissonis var. bipinnatisecta, Franseria chamissonis var. bipinnatisecta, Franseria chamissonis subsp. bipinnatisecta, Franseria villosa, Franseria chamissonis subsp. chamissonis, Ambrosia chamissonis f. bipinnatisecta

GBIF Accepted Name: Ambrosia chamissonis (Less.) Greene