Scientific Family
Asteraceae
Synonyms
Centaurea microcaeathina
Other common names
white knapweed
tumble knapweed
Plant type
Forbs and Subshrubs
Origin
Introduced
Lifecycle
Annual or perennial
Height
1 to 2 feet
Riparian
Yes
A robust diffusely branched and ball-shaped plant with a large taproot and a basal rosette of leaves. Smaller leaves appear on upright stems.
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.
Habitat
Listed as a noxious, prohibited weed in Arizona. Diffuse knapweed infests roadsides, waste areas, and dry rangelands.
Plant Community
Riparian
Pinyon Juniper Woodlands
Montane Conifer Forest
Interior Chaparral
Grasslands
Disturbed Areas
Desert Scrub
Low elevation
0
High elevation
7500
Flower Characteristics
Flowers grow out of bell-shaped heads and are surrounded by slender straw-colored spines.
Flower color
White to pink
Flower shape
Daisy or dandelion-like
Tubular
No
First bloom month
June
Last bloom month
August
Flower clusters
None
Leaf and Stem Characteristics
Leaves are resin spotted and stalkless. Stems are rough to the touch and gray-green.
Leaf type
Simple
Leaf color
Green
Leaf shape
Narrow
Leaf margin
Lobed
Leaves clasp
No
Leaf hairs
Leaves & stems
Spines
No
Fruit and Seed Characteristics
Fruit type
Achene
Fruit color
Dark brown
A single plant can produce as many as 18,000 barrel-shaped seeds per year.