Silver Beach Burrobrush

Ambrosia chamissonis, commonly called silver beach bur or silver beachweed, is a low, sprawling perennial of Pacific coastal sands. Silvery, hairy foliage forms broad mats that help cover dune and bluff soils; greenish flower heads are followed by prickly burs. ## Form and habitat Plants grow prostrate from a woody base and spread widely. A University of California Irvine natural history account describes loose mats about 1–3 m across and 15–30 cm high, while a Pacific Northwest flora gives a broader 6–40 inch height range. USDA Natural Resources Conservation Service restoration trials report more than 10 square feet of cover per plant and complete ground cover by the second year. Place it on sunny, freely draining coastal sand, dunes, cobble beaches, or bluffs where a spreading native ground cover is appropriate. It is poorly suited to small borders or footpaths because mature burs are spiny. ## Seasonal interest Silvery foliage contrasts with darker coastal plants. Small greenish flower heads appear through summer; this species is wind-pollinated. The USDA NRCS [coastal dune restoration guide](https://www.nrcs.usda.gov/plantmaterials/orpmcsr15058.pdf) documents habitat and field performance, and the [University of California Irvine natural history page](https://nathistoc.bio.uci.edu/Plants%20of%20Upper%20Newport%20Bay%20%28Robert%20De%20Ruff%29/Asteraceae/Ambrosia%20chamissonis.htm) describes its foliage and form. ## Maintenance Give new plants room to spread and water them during establishment. In a suitable coastal site, avoid routine disturbance of the sand-binding mat. Handle seed burs carefully because their spines can catch skin and clothing.