Annual bur-sage
Invasive Species Information

What Is Annual bur-sage - (Ambrosia artemisiifoIia)?

Habitat: Terrestrial
Distribution in Ireland:

Status: Established

Family name: Asteraceae

Common name/s: Ragweed, common ragweed

Reproduction: Characteristic flower head composed of numerous individual sessile flowers. The flower head consists of male flowers, while female flowers are located solitarily or in small groups with male and female owers in the same plant.

Annual bur-sage flowers

Common ragweed germinates in the spring (April) and grows rapidly during the juvenile phase under optimum condition promoting the competitive ability of the plant.

Ambrosia acanthicarpa is a North American species of bristly annual plants in the sunflower family. Members of the Ambrosia genus are called ragweeds.

The species has common names including flatspine bur ragweed, Hooker's bur-ragweed, annual burrweed, and annual bur-sage, and western sand-bur. The plant is common across much of the western United States and in the three Prairie Provinces of Canada.

Annual bur-sage stem and leaves

Annual bur-sage is a spiny, weedy plant growing in clumps of many upright stems which can reach over a meter in height. Grey-green stems are covered in stiff, bristly hairs.

Rough leaves are several centimeters long. The plant has numerous racemes of flowers with each hairy flower head a few millimeters wide.

Spiny, burr-like pistillate heads have pointed, twisting bracts and the staminate heads are rounded. The species is adaptable and grows well in disturbed areas, easily becoming weedy.

How To Identify Annual bur-sage?

ID Guide

Leaf: Fernlike - toothed leaves 4-10 cm long. Bright green on both sides with whitish nerves. Lower leaves arranged oppositely, with upper leaves often arranged alternately on the stem of mature plants.
Flower: Female flowers are solitarily or in small groups located at the base of upper leaves. Male flowers are small and green (2-4 mm) grouped in spike-like flower heads (racemes) at the end of the upper branches.
Stem: Reddish, hairy with a diameter of up to 2-4 cm at the base.
Fruit: Single seeded, red-dish-brown fruit (achenes), 3-4 mm long.

Annual bur-sage

Annual bur-sage seeds

Annual bur-sage leaf

Annual bur-sage flower

Why Is Annual bur-sage A Problem?

Annual bur-sage is an alien (non-native) invasive plant, meaning it out-competes crowds-out and displaces beneficial native plants that have been naturally growing in Ireland for centuries.

Annual sage-bur represents a very serious health risk for humans as pollen-allergenic plant. Pollen of ragweed is among the most potent triggers of hay fever and allergic rhinitis. In addition to allergic rhinitis, ragweed allergy often causes severe asthma-like symptoms. In Europe- and countries with large ragweed populations 10-20% of patients with pollen allergy symptoms suffer from ragweed- allergy.

Effect on biodiversity and recreation. Dense growth of common ragweed may lead to out-shading of existing vegetation and may be a threat to native species especially after a disturbance such as overgrazing which put competitive pressures on the native flora.

Annual sage-bur can also cause illness in livestock that ingest it and causes problems for the conservation and management of pastures.