Ambrosia chamissonis
silver beachweed
Overview
Ambrosia chamissonis is a sprawling, mat-forming perennial in the aster family native to Pacific coast beaches and foredunes. Trailing stems radiate 1.5-5 feet (0.5-1.5 m) from a deep taproot, forming low patches usually under 12 inches (30 cm) tall. The deeply lobed to twice-divided leaves are 1-4 inches (2.5-10 cm) long and covered in dense silvery-gray hairs that reflect sunlight and reduce water loss in the harsh dune environment. From June to October the plant bears slender spikes of small greenish flower heads; like other ragweeds it is wind-pollinated, and the male heads release abundant pollen that can trigger hay fever. Spiny burs about 0.25 inch (6 mm) wide enclose the seeds and disperse along the shoreline by wind and water. A. chamissonis anchors shifting sand and tolerates salt spray, drought, and nutrient-poor soils, but it does not withstand regular foot traffic or prolonged shade. It spreads both by seed and by rooting stems, stabilizing dunes where it establishes.
Native Range
Native to the Pacific coast of North America, from British Columbia south through Washington, Oregon, and California to Baja California, growing on beaches and coastal dunes.Suggested Uses
Used for dune stabilization, coastal restoration, and erosion control on sandy slopes. The silver foliage forms a low groundcover in seaside gardens. Its allergenic pollen makes it less suited to planting near patios and windows.How to Identify
Appearance
Size & Dimensions
Height4" - 1'
Width/Spread1'6" - 5'
Bloom Information
Detailed Descriptions
Foliage Description
silvery-grayGrowing Conditions
Sun Requirements
Requires 6-12 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