Flatspine Bur Ragweed

Ambrosia acanthicarpa, commonly known as Flatspine Bur Ragweed, is a perennial herbaceous plant native to the central and western regions of North America, particularly found in areas such as the Great Plains and parts of the southwestern United States. This species typically grows to a height of 30 to 90 centimeters (approximately 12 to 35 inches) and exhibits a bushy, upright form. Its stems are often branched and may be covered with fine hairs, contributing to its overall texture.

The leaves of Ambrosia acanthicarpa are deeply lobed and can vary in shape, generally measuring between 5 to 15 centimeters in length. They are typically dark green and have a rough, hairy surface. The flowering period occurs from late summer to early fall, during which the plant produces small, inconspicuous greenish-yellow flowers arranged in dense clusters. These flowers are wind-pollinated and are followed by the development of distinctive, spiny fruits that contain the seeds. The fruit is characterized by its flattened, spiny appearance, which aids in seed dispersal by attaching to the fur of passing animals or clothing.

Ecologically, Flatspine Bur Ragweed plays a significant role in its native habitat, providing food and shelter for various insects and wildlife. It is also a source of pollen, which can be allergenic to humans, particularly during its flowering season. The plant has adapted to thrive in disturbed soils and is often found in open fields, roadsides, and areas with low competition from other vegetation. Its ability to grow in a variety of soil types and conditions makes it a resilient species within its range.