This genus of one-year and perennial plants tally color to the late spring and summer garden .
Prized for its spicy petals , theCentaureagenus includes annuals and perennial . Bachelor ’s buttonor bluebottle is the most wide known genus Centaurea but it ’s not the only one worth engraft . A charming recurrent centaurea is mint bluet ( Centaurea montana ) .
These fast - growing , vivacious late - spring and early - summer bloomers have the casual growth substance abuse of wildflowers . Being fertile nectar producers , they are great for attracting butterflies . With their erect , unbranched stems , the thistle - same flower also make good cut flowers .
Credit: Denny Schrock
The genus also include the highly invasive spot knapweed ( Centaurea stoebe ) , sometimes called panicled knapweed , a species aboriginal to eastern Europe that has escaped finish in North America .
Where to Plant Centaurea
Plant centaurea in full or fond sun in any average , slenderly alkaline stain .
Centaurea bet best when planted in group or purport , either in mixed colour combinations or single color blocks . A full place for centaurea is in an informal or wildflower garden or a cutting flower garden . For an attractive reddish and blue display , interplant it with crimson poppies .
afterward in the summer , after the bloom , the foliage becomes middling unsightly . This can be mask by filling the infinite around the plants with other annuals and or perennials .
Credit: Denny Schrock
How and When to Plant Centaurea
Both annual and perennial genus Centaurea varieties are normally start from seeds .
embed them in the spring , either directly in the garden when temperature are systematically above 65 degrees F , orstart the seed indoorsabout one month before theaverage last frost in your area . If your wintertime are soft , you’re able to already plant yearly genus Centaurea in midfall for early saltation bloom . The plant will commence to grow before the first decline frost , then give way back over the winter and restart increase in the spring .
Cover the seeds with a ½-inch layer of filth and always keep the growth intermediate evenly moist . Annual centaura shoot in as small as 7 to 10 Clarence Shepard Day Jr. while repeated sort take 15 to 30 twenty-four hour period to germinate .
organ transplant seedling into the garden when they are 4 to 6 inch tall . Space one-year centaurea 12 inch apart . tenuous lineal - sown seedlings as needed . This snug spacing allows the plants to support each other .
Perennial centaurea call for more distance to spread , about 2 to 3 feet between plants . Taller varieties , include mountain bluet , may need stake for support .
To extend the shortsighted bloom period of annual genus Centaurea , part more seeds about three weeks after the first planting , and a third planting if desired .
Credit: Mike Jensen
Centaurea Care Tips
All type of genus Centaurea are easy - care garden ornamental .
Light
Choose a locating infull sunor partial tincture . In hot climates , a localisation with afternoon tone is preferred .
Soil and Water
Average garden dirt is all that genus Centaurea needs to thrive . Both one-year and perennial mintage tolerate a wide mountain chain of soil , from nimble - draining sandlike filth to heavy remains . While the plant grows in gently acidulent and indifferent soil , a pH of 7.0 or slightly aboveis nonesuch .
Because it is drought - resistant , centaurea seldom involve supplemental watering after it establishes a strong source system . Too much moisture subvert the works ’s stem and make it to become floppy .
Temperature and Humidity
Centaurea does best in a temperate climate . It fight in expanse with hot , humid summers .
Fertilizer
Like most wildflowers , the plant has down fertilizer needs . A one - time software of a balancedgranular dull - release fertilizerin the spring or at transplant fourth dimension is usually sufficient to sustain the flora during its active growing period .
Pruning
Deadheadingspent efflorescence spurs plant to grow unexampled bloom . This also controls the self - seeding of annual varieties .
Whether annual or perennial , genus Centaurea often takes on a bedraggled look in midsummer . When the foliage wilts and turns loose unripe and yellow , restore the plants by cutting them back by one - third or half . If temperate - to - cool weather prevails , expect centaurea to institutionalize up fresh foliation and flower stalks .
Potting and Repotting Centaurea
Centaurea does well in containers . ensure the container has drainage holes and fill it with a lightweight , well - drain potting mix . Although Centaurea is drought - insubordinate in the landscape , potted plants require more frequent watering .
Despite its winter hardiness , potted perennial centaurea needs winter shelter because growing it in a pot bring out its roots to ice and immobilize - and - thawing cps . Leave the potted plant outside during the winter but drop the pot in the ground to insulate the solution or place the potty in a 2d , larger gage to create a planting silo .
Annual centaurea does not require repotting . Perennial varieties should be repotted to a larger pot with fresh grunge or divided when the roots fill the container .
Credit: Dency Kane
Pests and Problems
Aphidsare a common pesterer launch on genus Centaurea . A simple yet effective way of restraint is launder the plants with a impregnable spray of H2O from a garden hose .
Especially in pissed weather , the plant life is prostrate to rust andpowdery mildew . Your first blood line of defense against these fungous diseases is insure good air circulation . take away infected leaves and stems promptly helps curb the spread .
How to Propagate Centaurea
In addition to propagation from seed , which is line underHow and When to Plant Centaureaabove , perennial centaureacan also be dividedevery two to three class . Division is also a beneficial room to check its rapid spread . In the spring , delve up the entire clump , divide it into diminished sections , and replant them at the same depth as the original plant .
Types of Centaurea
‘Amethyst in Snow’ Mountain Bluet
Centaurea montana’Amethyst in Snow ' is a cultivar that aggregate the good of the whitened and blue pattern of the coinage . A central purple forefront is set off by arrant - white re flowers . Zone 3 - 9
White Mountain Bluet
Centaurea montana’Alba ' , also know as clean recurrent bachelor’s button , is similar to the specie , but with blank peak instead of blue-blooded ones . Zone 3 - 9
Giant Knapweed
Centaurea macrocephala , also known as Armenian basketball hoop flower , is a marvelous species in the genus . It grow 4 to 5 feet tall with bright jaundiced , thistlelike flowers in midsummer . The species is aboriginal to the Caucasus , Iran , and Turkey . Zone 3 - 8
Singleflower Knapweed
Centaurea uniflorais an alpine species aboriginal to the mountains of cardinal and southeast Europe . It assume nongregarious purplish - pink flowers on a mound of prickly green leafage 15 to 20 inches tall . Zone 4 - 8
Perennial Bachelor’s Button
Centaurea pulcherrimaforms a low knoll of profoundly toothed gray - fleeceable leave of absence , which in former summer send up shaggy pinkish cornflower blooms . It is native to the Caucasus Mountains and tolerate hot , ironic term . zona 4 - 9
American Basketflower
Centaurea americanais an yearly coinage native to the southwesterly United States . Its fragrant , feathery , mauve flowers measure 4 inches across . With its potent prow and huge flush , it makes an excellent cut flower .
Centaurea Companion Plants
Poppy
Oriental poppieshave huge , break loose flower of brilliant red , pinks , blank , oranges , and plum , some with duple flowers in summer . Most are blotched with Shirley Temple Black at the base and center with a political boss of mordant stamen . They give their all at bloom time and the foliation dies back and look ragged , so project to replete the fresh available blank with yearbook , dahlias , baby ’s breath , or other later - blossom plant . geographical zone 2 - 8
Russian Sage
With its tall wispy wand of lavender or blue bloom and silvery foliage , Russian sageis an important player in summer and declination garden . It show off well against most blossom and provide an refined look to efflorescence borders . The aromatic leaves are oblong , deeply cut along the edges . Foot - longsighted panicles of blossom bloom for many week . fantabulous drain and full sunlight are idealistic , although very unclouded shade is tolerated . Plant near to void staking since the tall works be given to founder . Zone 4 - 9
Butterfly Weed
brilliantly coloredbutterfly weedis a butterfly magnet , attracting many sort of butterfly to its coloured prime . Monarch butterfly larvae provender on its farewell but rarely harm this native plant . It is tedious to emerge in the spring , so denounce its location to avoid accidental excavation before new growth startle . If you do n’t want it to spread out , deadhead faded blooms before pod mature . It is sometimes called milkweed because it produces a milklike sap when cut . Zone 3 - 11
Garden Plans for Centaurea
Easy Slope Garden Plan
The mix of easy annuals and hard perennials in thisgarden planwill beautify any slope . Shrubby Nanking cherries and bungalow garden favorite such as Shasta daisy , black - eyed Susans , and lupines add height and long - lasting colour to the innovation and do n’t require much maintenance . Lower - growing plants such as petunias , sedum , and candytuft fill in the place between them . The effect is a luxuriant , bloom - fill up exhibit that will look gorgeous from spring into fall .
Frequently Asked Questions
Cornflower , also known as bachelor ’s push button , is one of numerous species in theCentaureagenus .
While spotted knapweed is the most far-flung and most trespassing genus Centaurea , other extremity of the genus also have incursive tendencies . Bachelor ’s buttons is notorious for reseeding freely across lawns , gardens , and open space . To check the spread , deadhead the flowers of your plant before they sic seed .
Updated by Nadia Hassani
Credit: Peter Krumhardt
Credit: Peter Krumhardt
Credit: Peter Krumhardt
Credit: Matthew Benson
Credit: Jerry Pavia
