Plant Image
Flower head
Aspen Creek Tr - Sue Smith


Yavapai County Native & Naturalized Plants

Centaurea biebersteinii - spotted knapweed

Synonyms: Centaurea stoebe ssp. micranthus, Acosta maculosa, Centaurea maculosa
Plant Form: Forb

Family: Asteraceae


   
 
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Bracts
Aspen Creek Tr
Sue Smith
Leaf
Aspen Creek Tr
Sue Smith
Leaf attachment
Aspen Creek Tr
Sue Smith
Forb Plant Description

Origin: Introduced   Life Cycle: Biennial or perennial   Similar Species: Centaurea diffusa
General Desc: This invasive plant grows from a basal rosette in its first year into a bushy plant in its second year, blossoming with a profusion of small flowers for months and generating new rosettes for future growth.
Identification notes: Spotted knapweed is distinguished reliably by its "spots" or blackened bract ends. Pink to purple disc flowers only. Leaves divided into very narrow lobes, grayish-green.
Height: 8 inches to 4 feet


Habitat

Habitat Description: It prefers dry, coarsely textured soils that drain well, especially in south facing locations. It readily invades disturbed sites, choking out native vegetation, once established, it moves into surrounding more pristine areas.
Plant Communities: Disturbed Areas
Elevation: 1900 - 10000 feet


Flower Characteristics

Color: Pink to purple, rarely white     Shape: Daisy or dandelion-like not in clusters     Tubular: N     Flowering Period: Jun - Oct
Description: The flower can be 3/4 to 1 inch wide and when fully open is disc-like. The flower emerges from a cone of bracts, which distinguish the plant with their black tips and coarse bristles.


Leaf and Stem Characteristics

Leaf Color: Gray green to dark green     Leaf Type: Simple     Leaf Shape: Pinnatifid     Leaf Margin: Toothed     Leaf Attachment: Basal and alternate     Leaves Clasp: N
Hairs: Leaves and stems     Spines: N
Leaf Description: Erect, wiry stems that are green or gray in color branch freely at mid-height, producing 15 or more flowering stems. Leaves, which may be 6 inches long near the stem, are dotted with resin, narrow and deeply lobed, lobes are toothed at their end.


Fruit and Seed Characteristics

Fruit Color: Brown to black   
Fruit Type: Achene
Seed Notes: Seeds are oval with pale lengthwise lines and short fringe on one end.



  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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