Plant Image
Flower spike
Willow Lake - Sue Smith


Yavapai County Native & Naturalized Plants

Ambrosia psilostachya - western ragweed

Synonyms: Ambrosia californica, Ambrosia coronopifolia, Ambrosia cumanensis
Other Common Names: perennial ragweed
Plant Form: Forb or Subshrub

Family: Asteraceae


   
 
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Flower spike
Willow Lake
Sue Smith
Flower spike
Willow Lake
Sue Smith
Leaf
Willow Lake
Sue Smith
Leaf attachment
Willow Lake
Sue Smith
Plant - summer
Willow Lake
Sue Smith
Plant - summer
Willow Lake
Sue Smith
Forb Plant Description

Origin: Native   Life Cycle: Annual or perennial
General Desc: The plants are erect with a slender, branching, straw-colored stem rising from rhizome-like roots. Plants are monoecious with unisexual flowers. Western ragweed is one of the main hay-fever plants in late summer when it is in bloom.
Identification notes: Perennial rhizomatous herb. Leaves opposite and alternate, pinnatifid with broad midstripe, rough-hairy and glandular. Staminate heads pendant in terminal racemes; pistillate heads in upper leaf axils or in racemes below staminate heads.
Height: To 3 feet

Habitat

Habitat Description: Roadsides, disturbed places and along streams, often wet, alkaline, clay soils.
Plant Communities: Riparian, Disturbed Areas
Elevation: 850 - 7400 feet

Flower Characteristics

Color: Green, yellow     Shape: Bell-shaped in elongated clusters     Tubular: N     Flowering Period: Jul - Oct
Description: The male flower heads are numerous and contain 5 to 10 tiny yellow flowers. They occur at the top of the plant in elongated clusters arising from the upper leaf axils. Female flower heads are green, inconspicuous and are borne below in the leaf axils.

Leaf and Stem Characteristics

Leaf Color: Green     Leaf Type: Simple     Leaf Shape: Pinnatifid     Leaf Margin: Toothed     Leaf Attachment: Alternate and opposite     Leaves Clasp: N
Hairs: Leaves and stems     Spines: N
Leaf Description: The erect stems are slender and branched. Leaves are pinnately lobed. Lobes are entire or toothed. Lower leaves are opposite, upper leaves are alternate.

Fruit and Seed Characteristics

Fruit Color: Greenish-brown   
Fruit Type: Achene
Seed Notes: Short beaked bur, 1/8 to 1/4 inch long, with a few rounded projections.

  Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr #C
Prescott, AZ 86305
(928) 445-6590
Version 8.0  
http://cales.arizona.edu/yavapaiplants/SpeciesDetailForb.php  
Last Updated: Dec 13, 2022
Content Questions/Comments: Email Matt Halldorson  
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