Overview and Description
Although cornflowers are native to Europe, where they got their common name because they often grew in corn fields. They have made themselves at home in North American and can be found naturalizing throughout most of the continent. Because of their near true blue color and profuse bloom, they are popular garden flowers as well. Sometimes they grow too well; Tennessee and Maryland have reported cornflowers becoming invasive.
- Leaves: The lower leaves have a a curved lobe (lyrate-pinnatifid) but the majority of the leaves are narrow lanceolate, growing in whorls around the long stems.
- Flowers: The darker center flowers are surrounded by overlapping bracts and are about 1.5 in. across. The most widly known cornflowers are an almost true blue, but they also come in shades of white, pink, lavender, maroon and two-tones. The flowers are not just beautiful, they are also edible.
Cornflower, Bachelor's Button, Bluebottle, Garden Cornflower
To get the most blooms and sturdier stems, plant cornflowers in full sun. They can take a little shade, especially in the afternoon, but will perform best in all day sun.
Cornflowers have a somewhat bushy base with lots of long stems jutting out the top of the plant. While they will reach a mature size of about 1 - 3 ft. (h) x 1 - 2 ft.(w), most of the height is stems and flowers.
Peak bloom time is May through mid-summer, but you may be able to prolong the blooms with frequent deadheading.
Very often you will find seed that is simply labeled cornflower, cornflower mix or sometimes labeled by color. There are named varieties out there, but as new ones are introduced, older varieties can disappear. It's very easy to save your own seed though, if you should find a variety you truly love.
- Centaurea cyanus 'Blue Boy': Probably the most popular variety, with double flowers in "cornflower blue".
- Centaurea cyanus 'Black Magic': There are several dark purple flowered varieties, with 'Black' in their names.
- Centaurea cyanus 'Dwarf Blue Midget': bright, blue flowers on 6 - 12 in. plants. The dwarf varieties are nice for rock gardens and the front of a border or along edges.
Centaurea montana is a perennial cornflower that is hardy in USDA zones 3 - 8. It blooms in late spring.
Cornflowers are nice additions to all but the most formal gardens, They are traditional cottage and meadow plants, but they also make great cut flowers and dry very well. For long lasting cut flowers, cut them just before they are fully open, when the centers are still curving inward.
They complement most mid-spring flowers, from Bleeding Heart to spiky iris. The blue varieties blend well with pastels and are particularly striking next to yellow flowers and foliage.
Soil: Cornflowers are very adaptable and will grow in the poorest of soils. Ideally they prefer a neutral to slightly alkaline soil pH.
Planting: These are cool weather flowers, meant to go in the garden at the start of the season. If you'd like to get a head start, you can start seed indoors, 6 - 8 weeks before your last frost date. Seed also does well when direct sown right around the last spring frost date. Plants that are allowed to go to seed will probably self-sow.
Maintenance: Minimal watering and no fertilizer is needed to keep these annuals going. Established plants can tolerant dry soil, but regular water will keep the plants healthier.
The plants can become floppy and can be flattened by rain or wind. You could stake them while young or simply plant them near taller plants that will support the stems, as they grow.
You can deadhead, to prevent self-seeding, but many birds will eat the seeds.
Pests & Problems
Since cornflowers are grown as annuals, they don't usually have the time to develop serious problems. However they can occasionally be prone to powdery mildew, wilt, rust and rots and are attractive to aphids and mealybugs.