Plant Image
Flower head


Yavapai County Native & Naturalized Plants

Centaurea diffusa - diffuse knapweed

Synonyms: Centaurea microcaeathina
Other Common Names: white knapweed, tumble knapweed
Plant Form: Forb

Family: Asteraceae


   
 
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Plant
Max Licher @http://swbiodiversity.org
Forb Plant Description

Origin: Introduced   Life Cycle: Annual or perennial
General Desc: A robust diffusely branched and ball-shaped plant with a large taproot and a basal rosette of leaves. Smaller leaves appear on upright stems.
Identification notes: 1/2 inch long white to pink, blue, or purple flowers with 1/2 inch long involucres and principal phyllaries (bracts) tipped with less than 1/4 inch long spines distinguish this species from other Centaurea sp.
Height: 1 to 2 feet


Habitat

Habitat Description: Listed as a noxious, prohibited weed in Arizona. Diffuse knapweed infests roadsides, waste areas, and dry rangelands.
Plant Communities: Desert Scrub, Interior Chaparral, Semidesert Grasslands, Pinyon Juniper Woodland, Montane Conifer Forest, Riparian, Disturbed Areas
Elevation: Below 7500 feet


Flower Characteristics

Color: White to pink     Shape: Daisy or dandelion-like not in clusters     Tubular: N     Flowering Period: Jun - Aug
Description: Flowers grow out of bell-shaped heads and are surrounded by slender straw-colored spines.


Leaf and Stem Characteristics

Leaf Color: Green     Leaf Type: Simple     Leaf Shape: Narrow     Leaf Margin: Lobed     Leaf Attachment: Alternate     Leaves Clasp: N
Hairs: Leaves and stems     Spines: N
Leaf Description: Leaves are resin spotted and stalkless. Stems are rough to the touch and gray-green.


Fruit and Seed Characteristics

Fruit Color: Dark brown   
Fruit Type: Achene
Seed Notes: A single plant can produce as many as 18,000 barrel-shaped seeds per year.



  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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