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

Family: Asteraceae


   
 
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Flower spike
Willow Lake
Sue Smith
Flower spike
Willow Lake
Sue Smith
Leaf attachment
Willow Lake
Sue Smith
Leaf
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.
Height: To 3 feet


Habitat

Habitat Description: Roadsides, dry fields.
Plant Communities: Interior Chaparral, Semidesert Grasslands, Pinyon Juniper Woodland, Montane Conifer Forest, 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 5-10 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, 3-5 mm long, with a few rounded projections.



  Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr #C
Prescott, AZ 86305
(928) 445-6590
Version 7.0  
http://cals.arizona.edu/yavapaiplants/SpeciesDetailForb.php  
Last Updated: May 10, 2017  
Content Questions/Comments: Email Jeff Schalau  
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