Mexican Aster, Orange Cosmos, Yellow Cosmos, Cosmos bipinnatus, Cosmos sulphureus, Sulphur Cosmos, Cosmos atrosanguineus, Chocolate Cosmos
With finely cut leaves, showy flowers, and a long blooming season, Cosmos are half-hardy annuals or perennials blooming profusely from early or midsummer until fall, depending on varieties. Ridiculously easy to grow, fairly pest-free, and low maintenance, they attract birds, bees, and butterflies to your garden. They are grown in borders, in containers, and for cutting. They make excellent cut flowers thanks to their long vase life and richly colored petals, complementing any bouquet.
Native to Mexico, most of the cosmos flowers we grow derive from three species:
Highly sought after, Cosmos atrosanguineus are half-hardy, tuberous perennials boasting chocolate-scented, velvety deep crimson flowers, up to 2 in. across (5 cm), from midsummer to fall. Their pinnately divided leaves are often lobed at the base and are attached to the stems by winged petioles. These profuse bloomers create a striking visual impact in the garden and look outstanding when combined with ornamental grasses. They are also ideal in containers where their fragrance can be enjoyed.
True eye-catchers, Cosmos bipinnatus, are bushy, half-hardy annuals boasting single, semi-double, or double daisy-like flowers, as large as 5 in. across (12 cm), in a wide array of colors including pink, white, red, and bicolor varieties. Blooming for months from early summer to fall, the ravishing blossoms are borne atop branching stems and float above the fine, feathery foliage. Ranging from 2-5 ft (60-150 cm), tall varieties are ideal towards the back of mixed borders or in a row for cutting, while smaller cosmos varieties are perfect for the patio and terrace or at the front of borders.
| Hardiness |
2 - 11 |
|---|---|
| Heat Zones |
1 - 12 |
| Climate Zones | 1, 1A, 1B, 2, 2A, 2B, 3, 3A, 3B, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 |
| Plant Type | Annuals |
| Genus | Cosmos |
| Exposure | Full Sun |
| Season of Interest |
Summer (Early, Mid, Late) Fall |
| Height |
1' - 5' (30cm - 150cm) |
| Spread |
1' - 3' (30cm - 90cm) |
| Maintenance | Low |
| Water Needs | Low, Average |
| Soil Type | Chalk, Loam, Sand |
| Soil pH | Acid, Alkaline, Neutral |
| Soil Drainage | Moist but Well-Drained, Well-Drained |
| Characteristics | Cut Flowers, Showy |
| Tolerance | Drought |
| Attracts | Bees, Butterflies, Birds |
| Landscaping Ideas | Patio And Containers, Beds And Borders |
| Garden Styles | City and Courtyard, Cutting Garden, Traditional Garden |
Also called Orange Cosmos or Yellow Cosmos, Cosmos sulphureus are half-hardy annuals boasting vibrant, semi-double or double flowers, up to 2 in. across (5 cm), in shades of yellow, orange, or scarlet. Neat, with profuse blossoms and slightly broader, darker leaves, these cosmos generally grow up to 1-3 ft tall (30-90 cm) and perform very well in hot climates. Bringing showers of sparks in the landscape or containers, they can also be cut.
Cosmos flowers can be grown in a variety of locations and growing conditions. Here are some tips on where to grow cosmos:
Sunlight: Cosmos prefer full sun and will thrive in areas with at least 6 hours of direct sunlight per day.
Soil: Cosmos flowers prefer well-drained soil. They like soil that is not too rich, as rich soil will encourage foliage at the expense of bloom. They can grow in a variety of soil types but do best in soil that is slightly neutral to slightly alkaline in pH.
Water: Cosmos do not require frequent watering, but they do benefit from occasional deep watering during periods of drought or hot weather.
Climate: Cosmos are annual plants that can be grown in a wide range of climates. They are tolerant of heat, humidity and drought
Containers: Cosmos flowers can be grown in containers, making them a good choice for small spaces or balconies. Use a well-draining potting mix and water regularly to ensure healthy growth.
Garden beds: Cosmos flowers are often used in garden beds and borders and can be planted in groups or mass plantings for a dramatic effect. They can also be used to fill in gaps between other plants or to add color to an empty space.
Fertilizing: Cosmos planted in the garden generally do not require fertilizer, but if grown in containers, they can benefit from fertilization every two weeks or so using an all-purpose garden fertilizer to promote optimal flowering.
Deadheading: Regular deadheading of spent blooms can help encourage continued blooming and prolong the overall bloom season. Pinch off spent flowers or use sharp pruning shears to remove them.
Self-seeding: Cosmos flowers are known to readily self-seed. This means that once the flowers have finished blooming and the plant goes to seed, the seeds can drop to the ground and sprout on their own without the need for replanting. This can result in new plants growing in unexpected areas of the garden or landscape. If you want to control the location and number of cosmos plants in your garden, deadheading spent blooms before they go to seed can help prevent self-seeding.
Cosmos are versatile and easy to grow, and they can be paired with a wide range of companion plants to create a beautiful garden.
Zinnias: Zinnias are a natural companion plant for cosmos flowers, as they have similar growing requirements and complementary colors.
Marigolds: Marigolds are known for their pest-repelling properties and can help keep harmful insects away from your cosmos flowers.
Nasturtiums: Nasturtiums are a low-growing plant that can help shade the soil around cosmos flowers, helping to retain moisture and prevent weeds.
Sunflowers: Sunflowers are tall and sturdy plants that can provide support for taller varieties of cosmos, as well as add color and interest to the garden.
Salvia: Salvia plants are known for their beautiful, vibrant blooms and can complement the colors of cosmos flowers.
Sweet Alyssum: Sweet Alyssum is a low-growing plant that can be grown as a border or ground cover, adding a delicate and fragrant touch to your cosmos bed.
Cleome: Cleome plants, also known as spider flowers, have tall, spiky blooms that can add height and interest to a cosmos garden.
Sea Holly: Eryngium provides color and textural contrast, adding interest to any garden or landscape.
Tall Verbena: By pairing the delicate purple blooms and thin stems of verbena with cosmos flowers, you can create a contrast of textures that adds visual interest and variety to your garden.
Dahlia: By planting dahlia and cosmos together, you can create a layered effect that adds depth and dimension to your garden.
Cosmos are also perfect for mixing with roses (such as summer-long hybrid musks, English roses), buddlejas, border phlox, penstemon, monardas, campanulas, or veronicas.
They are also excellent companion plants in the orchard or vegetable garden and help crowded peas, lemons, and pomegranates.
Cosmos are resistant to most pests and diseases, but they can be affected by a few common problems. Here are some pests and diseases that can affect them:
Aphids: Aphids are small, soft-bodied insects that feed on the sap of plants. They can be controlled with insecticidal soap or neem oil.
Powdery mildew: Powdery mildew is a fungal disease that can cause a white, powdery coating to appear on the leaves of plants. It can be prevented by ensuring good air circulation around the plants and avoiding overhead watering.
Gray mold: Gray mold, also known as botrytis blight, is a fungal disease that typically appears as grayish-brown spots on the leaves and stems of the plant and can cause the flowers to rot and die. Improve air circulation, avoid overhead watering, remove infected parts, or use fungicides if the gray mold is severe.
Slugs: Slugs can eat holes in the leaves of cosmos flowers. They can be controlled by using slug bait or placing copper tape around the base of the plants.
Pictures are courtesy of National Garden Bureau, Benary, Botanik Foto, sakurai_dayo
| Hardiness |
2 - 11 |
|---|---|
| Heat Zones |
1 - 12 |
| Climate Zones | 1, 1A, 1B, 2, 2A, 2B, 3, 3A, 3B, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 |
| Plant Type | Annuals |
| Genus | Cosmos |
| Exposure | Full Sun |
| Season of Interest |
Summer (Early, Mid, Late) Fall |
| Height |
1' - 5' (30cm - 150cm) |
| Spread |
1' - 3' (30cm - 90cm) |
| Maintenance | Low |
| Water Needs | Low, Average |
| Soil Type | Chalk, Loam, Sand |
| Soil pH | Acid, Alkaline, Neutral |
| Soil Drainage | Moist but Well-Drained, Well-Drained |
| Characteristics | Cut Flowers, Showy |
| Tolerance | Drought |
| Attracts | Bees, Butterflies, Birds |
| Landscaping Ideas | Patio And Containers, Beds And Borders |
| Garden Styles | City and Courtyard, Cutting Garden, Traditional Garden |
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Create a membership account to save your garden designs and to view them on any device.
Becoming a contributing member of Gardenia is easy and can be done in just a few minutes. If you provide us with your name, email address and the payment of a modest $25 annual membership fee, you will become a full member, enabling you to design and save up to 25 of your garden design ideas.
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