By: Mary H. Dyer, Credentialed Garden Writer
Bachelor’s buttons, also known as cornflower or bluebottle, are old-fashioned flowers that reseed themselves generously from year to year. Should I deadhead bachelor’s button plants? These hardy annuals grow wild across much of the country, and although they require little care, pruning and deadheading bachelor’s buttons prolongs the blooming season. Read on and learn how to prune a bachelor’s button.
Feel free to cut back a bachelor’s button plant by about a third of its height about midsummer, or any time the plant looks scraggly and flowering begins to slow. Cutting back bachelor’s buttons tidies the plant and encourages it to put forth a new flush of flowers.
Deadheading bachelor’s buttons, on the other hand, should be done continuously throughout the blooming season. Why? Because bachelor’s buttons, like all plants, exist primarily to reproduce; when flowers wilt, seeds follow. Deadheading tricks the plant into blooming until the weather cools in late summer or early autumn.
Deadheading bachelor’s buttons is a simple task – just remove blooms as soon as they wilt. Use pruning shears, scissors or your fingernails to snip stems below the wilted flower, just above the next leaf or bud.
If you want the plant to reseed itself for blooms the following year, leave a few flowers on the plant at the end of the season. If you’re too diligent about deadheading, the plant will have no way to form seeds.
If you want to collect the seeds, let the flower wilt on the plant and watch for a seed head to develop at the base of the bloom. Roll the seed heads between your fingers to remove the wing-shaped seeds. Put the seeds in a paper sack until they are completely dry and brittle, then store them in a paper envelope in a cool, dry location.
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Read more about Bachelor Buttons
The Centaurea genus includes a number of annual and perennial species that are commonly known as cornflowers or bachelor's buttons. Centaurea montana is a popular perennial species, closely related to traditional cornflower (which is an annual plant), and often referred to as mountain cornflower, perennial cornflower, perennial bachelor's button, or mountain bluet.
Native to Europe, the mountain cornflower is a clump-forming plant with gray-green lance-shaped leaves. The flower's buds resembling tiny pineapples and open into charming flowers that have long blue petals with a lacy texture and reddish-purple centers. There are also cultivars available with white petals or a purple so deep that it is almost black.
Mountain cornflower is usually planted in spring, though potted nursery specimens can be planted any time of year in the proper USDA hardiness zone. 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||Mountain cornflower, perennial cornflower, perennial bachelor's button|
|Plant Type||Herbaceous perennial|
|Mature Size||1–2 ft. tall, 12–18 in. wide|
|Sun Exposure||Full sun|
|Soil Type||Dry to medium moisture, well-drained soil|
|Soil pH||Neutral to acidic, alkaline|
|Bloom Time||Late spring, early summer|
|Hardiness Zones||3–8 (USDA)|
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Anybody who grows perennials in their garden is familiar with the idea of cutting off the dead tops of their plants in late fall or early spring. By nature, most flowering perennials will die back to ground level in the fall, leaving behind their dried-up tops cutting these back at the appropriate time is a familiar and easily understood task.
There are many other pruning techniques that gardeners can make use of at other times of the season, in an effort to coax the best possible performance and garden worthiness from their perennials. These are less familiar tasks to most gardeners, but worth exploring at this point in the season when a quick and timely trim can produce some amazing results. I’ve broken the techniques into a few basic groups.
This idea is a simple one and fairly familiar: by trimming off the faded flowers, many perennials can be coaxed into producing more buds and flowers, rather than wasting their energy forming seeds. For certain plants (peonies, for instance), although no amount of deadheading will trick them into repeat bloom, plants look so much better after deadheading that it becomes part of the regular list of summer chores.
New gardeners often ask us how far down to cut below the flowers, but unfortunately it’s not always an easy thing to explain, each type of plant responding in a slightly different way. Experimentation is the best way to learn this after playing around with it for awhile, most gardeners sort of develop an instinct about where exactly the cut should be made. A few general tips:
Light Shearing Back
With many of the spring and early-summer flowering rock garden perennials, a light shearing after they finish flowering will keep them in top form for many years. This helps to maintain a dense and bushy habit, keeps them from dying out in the middle too quickly, and also prevents them from self seeding. Shear these types of plants back by half after flowering: Wall Cress (Arabis) Rock Cress (Aubrieta), Perennial Alyssum (Alyssum and Aurinia), Evergreen Candytuft (Iberis), and Moss Phlox (Phlox subulata).
Cutting Back Hard
With just a few exceptions, the vast majority of late spring and early summer-blooming perennials take a fast nosedive after flowering, and can look fairly hideous later in the summer. The mounding types of Cranesbill Geraniums and Silver Mound Artemisia are just two examples of plants that are notorious for looking terrible by July. With both of these a hard shearing back will encourage a new round of fresh, healthy and compact foliage to be produced, causing the plants to actually be an attractive addition to the border during the heat of summer. Cut Cranesbill Geraniums back more or less to just above the ground after blooming, taking care to leave the already-forming new foliage in the centre of the clump untouched. With Silver Mound, I like to shear the whole works back to 2 inches in height as soon as the tiny round silver ball-shaped flowers appear in mid to late June. This hard-pruning technique also works well with any of these: Lady’s Mantle (Alchemilla), Old-fashioned Bleedingheart (Dicentra spectabilis), Chrome Spurge (Euphorbia polychroma), Catmint (Nepeta), Blue Salvia, Meadow-rue (Thalictrum), Spiderwort (Tradescantia).
Pinching for Height Control
Pinching of fall-blooming Garden Mums (Chrysanthemum) is a familiar technique for most perennial gardeners. The same basic concept works for these late summer and fall bloomers: Monkshood (Aconitum), Michaelmas Daisies (Aster), Joe-pye Weed (Eupatorium), Helen’s Flower (Helenium), Beebalm (Monarda), Summer Phlox (Phlox paniculata), Autumn Stonecrop (Sedum) and many, many others.
June is the ideal time for cutting these back. Pruning off one half to two thirds of the growth will result in an especially bushy plant, with reduced height and often considerably more flowers, although smaller in size. This technique is especially useful to reduce the need for tedious staking. Pinching too late in the season can cause some of the autumn bloomers to flower so late that the frost gets the blooms before they have a chance to open. In general, pinching fall bloomers no later than the beginning to middle of July is wise, across Canada and in the northern States.
The Ultimate Pruning Reference
An indispensable reference book for the addicted perennial gardener is The Well-Tended Perennial Garden by Tracy DiSabato-Aust (1998, Timber Press ISBN 0-88192-414-8). Tracy’s colleagues refer to her as “the deadhead Queen”, and she offers an extremely thorough look at every aspect of perennial garden maintenance. Chapters on site and soil preparation, pests and diseases, plant selection, pruning methods, staking and everything else a gardener needs to do are both detailed and entertaining to read. Especially useful is the A to Z encyclopedia of perennials, with all the maintenance requirements for each plant laid out in a quick and concise format.
Cornflowers are extremely colourful hardy annuals. They look great in beds and borders, especially when part of an annual bedding display or a cottage garden, flowering from late spring and summer into autumn.
Cornflowers are also commonly known as ‘bachelor’s buttons’ – and more than a dozen other common names. They make excellent cut flowers and attract bees and butterflies and other pollinating and beneficial insects.
Although blue is the most common colour white, red, pink and purple varieties are also available.
Cornflowers grow and flower best in sunny positions. They need a fertile soil enriched with lots of organic matter, which holds plenty of moisture in spring and summer, doesn’t dry out or become waterlogged.
Sow seeds from March to May outdoors for flowers from June to September, or sow during August and September to flower slightly earlier the following year.
Sow seeds thinly in finely raked, moist soil where you want the plants to flower, at a depth of 13mm (½in) covering the seeds lightly with soil. Water the soil during dry periods.
Thin the seedlings in stages to 15-23cm (6-9in) apart when they’re large enough to handle.
You can buy young plants from garden centres, nurseries or mail order suppliers for planting in spring.
Dig over the planting area, incorporating lots of organic matter – such as compost or planting compost, especially if the soil is heavy clay or light, well-drained sandy soil. Dig a good sized hole big enough to easily accommodate the rootball.
Place the rootball in the planting hole and adjust the planting depth so that the crown of leaves is at soil level. Mix in more organic matter with the excavated soil and fill in the planting hole. Apply a general granular plant food over the soil around the plants and water in well.
Flower borders and beds, patios, containers, city and courtyard gardens, cottage and informal gardens, cut flower garden.
Water plants whenever necessary to keep the soil or compost moist during spring and summer, as this will prolong flowering.
Remove any competing weeds while the plants are young and establishing.
Applying a balanced liquid plant food every couple of weeks in the growing season will also encourage more, bigger and better flowers.
Deadhead plants regularly to prolong their flowering period well into autumn.
Pruning dead flowers from your plants is known as “Deadheading.” Basically, deadheading means the removal of flowers that have already put on their show. But should you cut back all perennial flowers? Deadheading is not the only part of pruning your Coreopsis. You should also trim the excess leaves and longer over growth. This video below demonstrates how to deadhead Coreopsis.
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