Ambrosia artemisiifolia (Annual Ragweed) - photos and description

 

 

 


Male flowers in above photo.


Male flowers in above photo.


Female flower in above photo.


Female flower in above photo.


Female flowers in above photo.


Female flowers in above photo.


Photo of fruit taken on September 7th.


Photo of fruit taken on September 7th.


Looking straight down on fruit, photo taken on September 7th.

General: Upright annual plants with a tap root. Its foliage is rough-hairy and greyish-green in colour.

Flowers: Flowers unisexual on the same plant. Male flowers many in terminal spikes, yellow, hang downwards. We measured a male flower at 2 mm in diameter, and a long spike at 10 cm long. Female flowers single or in clusters in leaf axils, the female flowers have divided styles, we measured a female flower at 3 mm long.

Fruit: Fruit is egg-shaped, with a terminal beak surrounded by a ring (a single row) of short spines, spines less than 1 mm long. We measured a fruit at 3 mm long.

Leaves: Leaves are alternate, all cauline, petiolate, broadly ovate, pinnately twice-divided into narrow lobes. Leaves divided almost to the midrib. The leaf highlighted in the photo above was measured at 85 mm long and 75 mm wide.

Height: Height listed in Budd's Flora to 90 cm, we measured plants growing to 61 cm tall.

Habitat: Roadsides and waste ground.

Abundance: Listed as common, has been uncommon in our experience, we've only seen this plant in one location.

Origin: Native.

How to identify this species of Ambrosia: Annual, leaves divided right to midrib (Taxonomic Reminder for Recognizing Saskatchewan Plants).

Similar species: This plant is very similar to Ambrosia psilostachya (perennial Ragweed).

Ambrosia psilostachya is rhizomatous, leaves once pinnatifid, and has leaves not divided wholly to midrib, while similar species Ambrosia artemisifolia has a taproot, lower leaves twice pinnatifid, and leaves divided to midrib.

When and where photographed: We took the above photos on August 5th and September 7th on a dusty prairie roadside, Souris River valley, 225 km southeast of our home in Regina, SK.