How to Grow and Care for Mountain Cornflower

Mountain cornflower (Centaurea montana), is a popular perennial species closely related to the annual cornflower or bachelor's button Centaurea cyranus. Native to Europe, this clump-forming plant bears gray-green lance-shaped leaves and flower buds that resemble tiny pineapples. The charming solitary, fringed, blue flowers have reddish blue centers. Cultivars feature white flowers or a deep, almost black purple.

Mountain cornflower likes to be planted in the spring, though starts may take a full year or two to establish themselves. Once mature, this plant colonizes nicely and can live for 15 years or more. Do note, however, that mountain cornflower can be invasive when not cared for properly and kept in check.

Mountain Cornflower Care

Mountain cornflower is an easy-to-care-for varietal that grows well when planted in a sunny location. This low-maintenance plant simply requires well-drained soil and the removal of volunteers every few years to prevent vigorous spread. The plant's flowers can be appreciated on their own or combined with other flowers to create a striking contrast. Deadhead the blooms after flowering to encourage a late summer rebloom. Some gardeners also like to aggressively prune the stems after a mid-summer bloom to rejuvenate the entire clump with new foliage.

Because of its drought tolerance, mountain cornflower makes a good addition to rock gardens. It's also a good choice for a butterfly or pollinator garden. If you live in a region where perennial cornflower has naturalized, combine it with various types of native plants to form a wildflower garden.

Light

Plant your mountain cornflower in a spot that receives six to eight hours of full sun each day for optimal flowering. This plant can tolerate light shade, but locations that have too much shade can cause a reduction in blooms and make the plant grow spindly and floppy.

Soil

Mountain cornflower needs sandy, well-drained soil to thrive, and it can tolerate dry, nutritionally poor soil quite well. This plant does not thrive in especially rich soils. Mountain cornflower isn't that picky about soil pH either and can tolerate a range of levels, from 6.1 to 7.8.

Water

Once established, mountain cornflower is drought-tolerant and requires only a weekly watering during dry spells. Take care not to overwater this plant, as its stems rely on dry, rigid ground to keep them upright. Young plants, however, will need adequate water (several times a week) until established. Increase your watering cadence slightly during especially hot temperatures. This plant is best served with drip irrigation, as sprinkling from above can damage its fragile stems.

Temperature and Humidity

Mountain cornflower, as its name suggests, is native to the high-altitude meadows and woodland areas of central and southern Europe. That said, it grows well in all climate variations within its hardiness range but is an especially vigorous grower in northern climates. This flower prefers temperatures ranging from 59 F to 78 F and can even survive a light frost. Mountain cornflower likes things dry and does not grow well in a hot and humid environment.

Fertilizer

This easy-to-care-for plant dislikes rich soil. It needs virtually no feeding—not even an annual soil amendment with organic material. A single spring feeding is occasionally useful for plants growing in very poor soil conditions, but even then, fertilization is not necessary.

Types of Mountain Cornflower

Cultivars of mountain cornflower can be characterized by their colors, foliage, or growth pattern. Choose the type that best serves your gardening goals, keeping in mind that every variety is equally appealing.

Here are some gardeners' favorites:

• 'Amethyst Dream' boasts lacy, deep purple petals with an even darker center. This type forms a low mound of grey-green leaves and makes a great border.
• 'Amethyst in Snow' is a unique spreading varietal that makes a good ground cover. It features fringe-like white petals surrounding a purple center.
• 'Alba' features snowflake-like white flower petals around a pink center. It grows up to 18 inches tall and spreads to 12 inches wide.
• 'Black Sprite' bears star-burst-shaped flowers of dark purple and blooms early in the summer. The cut flowers and spent blooms of this type don't turn brown once dry.
• 'Carnea' is especially popular since it is the only pink cultivar and flowers all season long. This type grows to a mature height and spread of 15 inches.

Pruning

Proper pruning influences the length of mountain cornflower's bloom time, as well as its spread. To encourage a bushier spread, pinch back the ends of new growth early in the spring. Then, if desired, pinch off one-third of the plant's buds to make the blooms larger. Once the first bloom period is over, snip off spent flowers to the first set of leaves to encourage another bloom. Annually, pull up volunteers to control spreading and divide the plant in the spring every two years.

Propagating Mountain Cornflower

Dividing mountain cornflower clumps helps maintain the plant's vigor and control its spread. Divisions can be planted elsewhere in your garden, gifted to friends, or transplanted into pots.

Here's how to propagate mountain cornflower through division:

1. Gather gloves, a spade shovel, a garden trowel, and garden shears.
2. In the spring after the first growth appears, dig up your cornflower clump and place it on its side on the ground.
3. Carefully pull apart sections that contain both growth and root using your trowel.
4. Dig new holes for the individual plants and snip away any dead growth.
5. Plant each new plant in a hole, backfilling to cover the roots. Relocate the mother plant to its existing hole and backfill in the same manner.
6. Water all the plants thoroughly and keep the soil moist until the plants mature.

How to Grow Mountain Cornflower from Seed

Mountain cornflowers will readily self-seed in your garden, but you can seed a garden bed yourself. Seeds can be purchased from a garden center or collected from last year's flowers. Sow the seeds indoors eight weeks before your average last frost date by broadcasting them over a seed tray filled with seed-starting mix. Make sure to fully cover your seeds with soil, as they need complete darkness to sprout. Water the tray and keep the soil moist until seedlings appear in three to four weeks. Pull weak seedlings, allowing the others to grow, and transplant the hardy ones outside when the soil temperature reaches 60 F.

Potting and Repotting

Mountain cornflower makes a statement when grown in pots and containers. Select a clay or terracotta pot with several drain holes. Fill the pot with well-drained potting soil containing vermiculite or soilless medium. Mix in other annuals or perennials that prefer the same conditions. Once planted, water thoroughly and allow the pot to drain completely. Place your cornflower in a sunny spot to encourage blooms and make sure not to overwater it.

Overwintering

Mountain cornflower has adapted well to high-altitude and northern climates, eliminating the need to protect it during the winter. All that is needed to winterize this plant is a good cutback to the ground in late fall. Come spring, new growth will emerge from the cultivated mound.

Common Pests & Plant Diseases

There are few serious disease issues with mountain cornflower. Non-fatal fungal rust or mildew infections sometimes occur. To avoid these issues, make sure to give your cornflower clumps enough distance between plants and prune them around the center to aid in air circulation.

Aphids can move into a patch of mountain cornflower but can be easily controlled by reducing their population with several blasts from the garden hose. You can also use a soap and water spray to eliminate any lingerers. A stalk borer infection, while rare, can cause plant fatality, and your only indication may be a wilting plant that doesn't recover. While this condition is untreatable, you can prevent it by regularly weeding your garden and pruning last year's dead growth.

How to Get Mountain Cornflower to Bloom

Cornflowers bloom best when planted in full sun and deadheaded regularly. Removing old blooms will stimulate the plant to make new ones, and pruning encourages bigger blooms. If you have a particularly finicky patch that doesn't seem to bloom, try adding an organic fertilizer high in phosphate. While cornflower usually prefers no fertilization, this little boost may help a sluggish patch bloom.

Common Problems With Mountain Cornflower

Mountain cornflower can become invasive if not kept in check. Natively, it grows rampant in nutrient-poor soil throughout corn and grain fields in Europe and is considered a weed. In naturalized areas, this plant can take over in just a few seasons, making it necessary to pluck volunteers and divide root clumps on a bi-annual basis to avoid mass proliferation.