Giant knapweed

Centaurea macrocephala

Photo/Illustration: 
Jennifer Benner
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Giant knapweed (Centaurea macrocephala)
Genus:  Centaurea
This clumping, robust perennial has unusual ramrod-stiff flower stems that bloom from early summer through late summer. Its fat, rusty buds open into large, deep yellow thistle flowers the size of a small fist. Easy to cut and dry for arrangements. This plant has big, coarse leaves that call for strong companions.
Noteworthy Characteristics:  A tricky plant to work into a perennial garden because it draws a lot of attention.
Care:  Grow in moist soil in sun or partial shade.
Propagation:  Start seeds in a cold frame in spring, or divide plants in spring or fall.
Problems:  White mold, rust, mildews, thread blight, and Southern blight.

Overview

Height
3 ft. to 6 ft.
Spread
1 ft. to 3 ft.
Growth Habit
Clumps
Light
Full Sun to Part Shade
Moisture
Medium Moisture
Characteristics
Showy Flowers
Bloom Time
Summer
Flower Color
Primrose Yellow
Uses
Cottage Garden,
Cut Flower
Style
Rock Garden
Seasonal Interest
Summer Interest
Type
Perennials

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