Plant cosmos flowers to enjoy cheerful pink, white, red and yellow blooms over tall, feathery foliage all summer long. Cosmos flowers are ideal for a butterfly or bird garden, and are a natural companion for vegetables in organic gardens, as they attract these pollinators. They make superb cut flowers and look right at home growing randomly in wildflower gardens. It is easy to grow cosmos flowers from seed, although nurseries stock seedlings in early summer. When they are happy, cosmos flowers self-seed freely, offering you a profusion of blooms between June and October year after year.
Perennial flowers, such as cosmos, grow from seed, bloom, set seed and die within the course of one growing season. Poppies, sunflowers and impatiens are examples of other perennial flowers. Self-seeding occurs when flowers that have bloomed and set seed distribute their seeds in the area. Wind, weather and animals can help distribute annual seeds.
As you become familiar with growing cosmos flowers, you will recognize the shoots they send up the following spring. You can then determine whether you want to keep the new cosmos in the location where they sprouted or attempt to move them. Moving self-seeded annuals can sometimes be tricky, as they prefer to grow where they plant themselves. But, it is worth a try, especially if cosmos self-seed in a location where they will cast shade over other plants in the garden.
Cosmos flowers can grow from one to four feet tall. Place them in the middle or towards the back of borders that contain shorter plants. You can grow dwarf varieties of cosmos nearer to the front of the border. Dwarf cosmos are also suitable for small pots. Standard cosmos flowers' relatively tall height makes them a good choice for adding drama to a garden. You can mix them with other tall plants, grasses and wildflowers to create a lush field of colorful blooms that are especially eye-catching when they blow in the wind.
Cosmos flowers require full sun. They will not bloom prolifically in partial shade and will not bloom at all in shaded areas. Consider the location where you want to plant cosmos carefully to ensure that the flowers will get enough sun to bloom.
Cosmos flowers thrive in moist, well-drained soil. It is especially important to water seedlings that have just sprouted to ensure that they do not dry out. Once plants are established, rainfall is generally adequate to meet their needs. However, plants will die if they do not get enough water. Do not overwater plants or they will become waterlogged and die. Planting cosmos in areas with loose, well-draining soil provides the best moisture conditions for their growth.
Container gardens benefit from the addition of cosmos flowers. Ensure that tall varieties of cosmos flowers have a large pot with adequate support so that tall stems do not blow over or snap in windy or harsh weather conditions. Dwarf varieties are well-suited to containers. Choose pots that contrast with the happy red, pink, white or yellow blooms. Try growing hot pink cosmos in large, cobalt blue pots in clusters on both sides of a sunny patio staircase for a warm, tropical feel. Consider all-white dwarf cosmos in rich cocoa glazed ceramics as part of a mixed container arrangement that includes red roses in larger pots glazed in earth tones placed against a backdrop of white clematis growing up a trellis.
Create a butterfly garden by combining cosmos with flowers such as zinnias, sweet pea, lilac, bee balm and sunflowers. When choosing flowers to combine with cosmos, consider varieties that feature colors and growing habits that suit your taste and space requirements and need the same light and moisture conditions as cosmos. A cosmos-heavy wildflower garden is easy to enjoy when you plant it near outdoor seating areas and below windows where you can view them from inside.
Hot pink cosmos seem to glow in late autumn; try mixing them into your vegetable garden to keep the show going until the first frost. They look especially great when mixed with asparagus plants, as asparagus sends up frothy leaves similar in texture to the cosmos plants. The blooms can keep the asparagus patch attractive well after you have picked and eaten the last spears of the vegetable.
"Chocolate" cosmos blooms are a dark red that appears almost brown. They look handsome in a brown and cream garden. One of these gardens could include other austere features, such as a mix of low-growing ferns, "chocolate" hucheras and Japanese maple trees.
It isn't necessary to start cosmos seeds indoors. Select an outdoor location with full sun and good drainage. Prepare the soil by loosening it to a depth of at least one foot and enriching it with a small amount of organic matter, such as compost.
Plant seeds in late spring after all danger of frost has passed. Plant them at a depth of twice to three times the length of the seeds and a distance of several inches apart, then cover them with soil. Tamp down the soil to ensure that seeds are making good contact. Water seeds, keeping them moist, but not soaked until you see the first shoots. Thin the seedlings to a distance of about 12 inches to ensure that each cosmos plant has plenty of room to grow. Allow only 8 inches between plants for fast coverage, but be aware that the plants may eventually become crowded and inhibit each other's blooms.
Make sure to plant cosmos seeds in positions north of shorter plants that also require full sun, or you risk that the taller cosmos will cast shadows over them and inhibit their growth. You can also find seedlings in nurseries at the beginning of summer. Transplant seedlings into a sunny prepared spot in the garden and water them thoroughly to encourage them to set root.
Cosmos can suffer from powdery mildew in extremely damp or crowded conditions. Aphids can be a problem, especially if nearby plants are suffering from an infestation. Good garden clean-up habits reduce the risk of pests and disease for cosmos and for all garden plantings. Never weed or cut plants during damp weather, and keep the garden well weeded to avoid problems. Do not over-fertilize cosmos flowers or they will grow lots of greenery with few blooms.