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Centaurea jacea

brown knapweed

Asteraceae Europe and western Asia

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant

SunFull Sun – Part Shade

WaterLow · drought-tolerant

HardinessZones 4–8

Overview

Centaurea jacea is an upright perennial growing 12-40 inches (30-100 cm) tall on branching, slightly rough stems from a woody base. The lance-shaped leaves are 2-6 inches (5-15 cm) long, mostly entire or slightly toothed, the lower ones stalked and the upper ones stalkless. Thistle-like flower heads 0.6-1.5 inches (1.5-4 cm) across appear from June to September, with rose-purple florets surrounding a button-like center, set above a rounded base of papery brown bracts that give the plant its common name. Unlike true thistles, the plant has no spines. The fruit is a small seed with little or no tuft of bristles. Plants grow from a deep root and self-seed, forming clumps in grassland and along verges. It is one of several knapweeds naturalized in North America, where some are treated as invasive rangeland weeds. Foliage dies back in winter and regrows from the crown. The flowers draw bees and butterflies through summer.

Native Range

Native to Europe and western Asia, in meadows, pastures, grassy banks, and woodland edges. Naturalized in North America and elsewhere, where it grows on roadsides, fields, and disturbed grassland.

Suggested Uses

Used in wildflower meadows, naturalistic grassland, and pollinator plantings, spaced 12-18 inches (30-45 cm) apart. Suits meadow seed mixes where its self-seeding is acceptable. Several knapweeds are regulated as invasive in parts of North America, where planting is restricted.

How to Identify

Recognized by rose-purple thistle-like flower heads 0.6-1.5 inches (1.5-4 cm) across without spines, set above a rounded base of papery brown bracts. The lance-shaped, mostly untoothed leaves and branching spineless stems are characteristic. Distinguished from spotted and other knapweeds by its rounded, light brown bracts with ragged or torn margins rather than dark-fringed bracts.

Appearance

Size & Dimensions

Height1' - 3'4"

Width/Spread1' - 1'6"

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~14 weeks

Summer Fall

Flowers from June through September, peaking in midsummer. Individual heads open over a few days, and the plant carries flowers and seed at the same time across a long season. Bloom may continue into October in mild autumns.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-9 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 8.0(Neutral)

357912

Soil Types

loam sand chalk clay

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

1-2 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grows in full sun to light shade on a wide range of soils, including poor, dry, and lime-rich ground. Tolerates drought once established through its deep root and needs no supplemental water in most climates. Self-seeds freely and can spread into grassland and borders, so removing seed heads before they ripen limits spread. No serious pests or diseases affect it. It withstands cutting and grazing and regrows from the crown. Several knapweeds are regulated as noxious weeds in parts of North America under state and provincial laws.

Pruning

Cut or deadhead spent flower heads before seed ripens to limit self-seeding. Shear or mow plants in meadow settings after flowering once seed has set. Cut back remaining stems in late autumn or early spring.

✓ Toxicity

Non-toxic