This genus of annual and perennial plants adds color to the late spring and summer garden.
A charming perennial centaurea is mountain bluet (Centaurea montana).
These fast-growing, vivacious late-spring and early-summer bloomers have the casual growth habit of wildflowers.
Credit: Denny Schrock
Being prolific nectar producers, they are great for attracting butterflies.
With their erect, unbranched stems, the thistle-like blooms also make good cut flowers.
Centaurea looks best when planted in groups or drifts, either in mixed color combinations or single color blocks.
Credit: Denny Schrock
A good place for centaurea is in an informal or wildflower garden or a cut flower garden.
For an attractive red and blue display, interplant it with red poppies.
Later in the summer, after the bloom, the foliage becomes somewhat unsightly.
This can be disguised by filling the space around the plants with other annuals and or perennials.
How and When to Plant Centaurea
Both annual and perennial centaurea varieties are commonly started from seeds.
Cover the seeds with a 12-inch layer of soil and always keep the growth medium evenly moist.
Credit: Mike Jensen
Transplant seedlings into the garden when they are 4 to 6 inches tall.
Space annual centaurea 12 inches apart.
Thin direct-sown seedlings as needed.
Credit: Dency Kane
This close spacing allows the plants to support each other.
Perennial centaurea need more space to spread, about 2 to 3 feet between plants.
Taller varieties, including mountain bluet, may need staking for support.
Credit: Peter Krumhardt
Centaurea Care Tips
All types of centaurea are easy-care garden ornamentals.
Light
Choose a location infull sunor partial shade.
In hot climates, a location with afternoon shade is preferable.
Credit: Peter Krumhardt
Soil and Water
Average garden soil is all that centaurea needs to thrive.
Both annual and perennial species tolerate a wide range of soils, from quick-draining sandy soil to heavy clay.
While the plant grows in mildly acidic and neutral soil,a pH of 7.0 or slightly aboveis ideal.
Credit: Peter Krumhardt
Because it is drought-tolerant, centaurea rarely needs supplemental watering after it establishes a strong root system.
Too much moisture weakens the plant’s stem and causes it to become floppy.
Temperature and Humidity
Centaurea does best in a temperate climate.
Credit: Matthew Benson
It struggles in areas with hot, humid summers.
Fertilizer
Like most wildflowers, the plant has low fertilizer needs.
Pruning
Deadheadingspent blooms spurs plants to produce new flowers.
Credit: Jerry Pavia
This also controls the self-seeding of annual varieties.
Whether annual or perennial, centaurea often takes on a bedraggled look in midsummer.
If moderate-to-cool weather prevails, expect centaurea to send up fresh foliage and flower stalks.
Potting and Repotting Centaurea
Centaurea does well in containers.
double-check the container has drainage holes and fill it with a lightweight, well-draining potting mix.
Although Centaurea is drought-resistant in the landscape, potted plants need more frequent watering.
Annual centaurea does not require repotting.
Pests and Problems
Aphidsare a common pest found on centaurea.
Especially in wet weather, the plant is prone to rust andpowdery mildew.
Your first line of defense against these fungal diseases is ensuring good air circulation.
Removing infected leaves and stems promptly helps contain the spread.
Division is also a good way to control its rapid spread.
A central purple head is set off by pure-white ray flowers.
It grows 4 to 5 feet tall with bright yellow, thistlelike flowers in midsummer.
The species is native to the Caucasus, Iran, and Turkey.
It bears solitary purplish-pink flowers on a mound of prickly green leaves 15 to 20 inches tall.
It is native to the Caucasus Mountains and tolerates hot, dry conditions.
Zone 4-9
American Basketflower
Centaurea americanais an annual species native to the southwestern United States.
Its fragrant, feathery, mauve flowers measure 4 inches across.
With its strong stems and huge flowers, it makes an excellent cut flower.
Most are blotched with black at the base and centered with a boss of black stamens.
It shows off well against most flowers and provides an elegant look to flower borders.
The aromatic leaves are oblong, deeply cut along the edges.
Foot-long panicles of flowers bloom for many weeks.
Excellent drainage and full sun are ideal, although very light shade is tolerated.
Plant close to avoid staking since the tall plants tend to flop.
Monarch butterfly larvae feed on its leaves but seldom harm this native plant.
If you don’t want it to spread, deadhead faded blooms before seedpods mature.
It is sometimes called milkweed because it produces a milky sap when cut.
Lower-growing plants such as petunias, sedum, and candytuft fill in the spaces between them.
The effect is a lush, bloom-filled display that will look gorgeous from spring into fall.
Bachelor’s buttons is notorious for reseeding freely across lawns, gardens, and open spaces.
To curb the spreading, deadhead the flowers of your plant before they set seed.
