The Centaurea genus includes a number of annual and perennial species that are commonly known as cornflowers or bachelor's buttons, but C. Montana is a popular perennial species. It may be known as perennial cornflower, perennial bachelor's button, mountain cornflower, or mountain bluet.
Perennial cornflower is a clump-forming plant with gray-green lance-shaped leaves. The flower buds, resembling tiny pineapples, open into exotic flowers with long blue petals with a lacy texture, around reddish-purple centers. There are also cultivars available with white petals or a purple so deep that it is almost black.
Perennial cornflower is usually planted in spring, though potted nursery specimens can be planted whenever you want. A small potted specimen may take a full year or two to become established, but then will colonize nicely and may live for 15 years or more.
|Botanical Name||Centaurea montana|
|Common Names||Perennial cornflower, perennial bachelor's button,|
|Plant Type||Herbaceous perennial|
|Mature Size||1 to 2 feet tall; 12- to 18-inch spread|
|Sun Exposure||Full sun|
|Soil Type||Dry to medium moisture, well-drained soil|
|Soil pH||6.1 to 7.8 (slightly acidic to slightly alkaline)|
|Bloom Time||May to June|
|Flower Color||Blue with reddish-purple centers|
|Hardiness Zones||3 to 9 (USDA)|
|Native Area||Central and Southern Europe|
How to Grow Perennial Cornflower
Perennial cornflower will do well in almost any well-draining soil in a sunny location. Little care is required, though you may need to remove volunteer seedlings or divide the plant every few years to prevent it from spreading.
Deadhead after flowering to encourage reblooming in late summer, although the second blooming typically won't be as vigorous as the first one. Some gardeners like to prune them back quite hard mid-summer to rejuvenate the entire clump with new foliage.
There are few serious insect or disease problems with perennial cornflower, although non-fatal fungal rust or mildew infections sometimes occur.
Plant this perennial in full sun for optimal flowering. Shady locations will make the plant floppy and reduce flowering.
Perennial cornflower needs a well-drained soil in which to grow, and it tolerates dry soils quite well. It will tolerate pH levels from 6.1 to 7.8 (slightly acidic to slightly alkaline). It does not grow well in extremely rich soils.
Once established, these will be drought-tolerant perennials; take care not to over-water. But young plants will need adequate water to become established.
Temperature and Humidity
This plant is native to the meadows and woodland areas of central and southern Europe. It does well in virtually all climate variations through its hardiness range, Zones 3 to 9, but it is especially vigorous in the cooler northern climates. Here, you should avoid feeding it, as it can grow out of control.
This is one of those plants that seems to dislike rich soil. It needs virtually no feeding—not even soil amendment with organic material. A single spring feeding is occasionally useful for plants growing in hot climates and in very poor soil.
Propagating Perennial Cornflower
Perennial cornflower will readily self-seed in the garden, and the volunteers can easily be transplanted to other locations. More commonly, the entire perennial cornflower clump is divided every two to three years, with the clump pieces transplanted elsewhere.
Varieties of Perennial Cornflower
- 'Amethyst Dream' has flowers with lacy royal blue petals around a darker purple center.
- 'Amethyst in Snow' has fringe-like white petals surrounding a purplish center. It has a spreading growth habit that makes it a good choice as a ground cover.
- 'Alba' has pure white flower petals around pinkish centers.
- 'Gold Bullion' has the standard purple flowers, but features foliage that is a lighter chartreuse color.
- 'Black Sprite' has star-burst shaped flowers of dark purple around similarly dark centers.
- 'Carnea' is a variety featuring pink blossoms.
Perennial Cornflower vs. Other Centaurea Species
Centaurea montana is just the tip of the iceberg when it comes to types of Centaurea. Another closely related species is a yellow Centaurea, C. macrocephala. Centaurea montana and Centaurea macrocephala are both perennials, but there is also an annual bachelor button (Centaurea cyanus). The fact that all these species are often called cornflowers reflects the fact that these plants are a common sight in the cornfields of southern Europe.
No doubt, the outstanding feature of this plant is its delicate flowers. They display a fine texture that can either be appreciated in its own right or set off against flowers of different colors or coarser texture to create a striking contrast.
In regions where perennial cornflowers tend to become naturalized plants, they can be grown with various types of native plants to form a wildflower garden. Because of their drought-resistance, perennial cornflowers are useful in large rock gardens. They have traditionally been used in cottage gardens and, more generally, make good edging plants. They are also a good choice for butterfly gardens.