[3] It is known from most of the coastline of western North America from Alaska to Baja California, where it is a resident of beaches and other sandy coastal habitats.

[4][5] Ambrosia chamissonis is a large, sprawling perennial herb exceeding 3 metres (9.8 ft) in maximum width.

The plentiful leaves are a few centimeters long, woolly and silver-green, and variable in shape.

Each pistillate head contains a single tiny flower which develops into a fruit.

The fruit is a brown bur up to a centimeter wide covered in sharp spines.