Cosmos Plants

Cosmos Plants FAQs

Take a look at some of the frequently asked questions we receive from those looking to buy Cosmos Plants in the UK. You can contact our Customer Service Team or browse our general FAQs for further advice.

When to plant Cosmos Plants

Plant Cosmos plants in the spring after the last frost date for your region. They prefer warm soil, so wait until soil temperatures have reached around 60°F (15°C). This timing typically falls between late April and early June, depending on your location. Sow seeds directly into well-drained soil or transplant seedlings into your garden beds or containers once all danger of frost has passed. This timing allows Cosmos plants to establish themselves and produce abundant blooms throughout the summer and into the fall.

How to Plant Cosmos Plants

To plant Cosmos plants, start by selecting a sunny location with well-draining soil. Prepare the soil by loosening it to a depth of about 6 inches and removing any weeds or debris. If starting from seeds, sow them directly into the prepared soil after the last frost date for your area, spacing them about 12 to 18 inches apart. Alternatively, you can start seeds indoors 4 to 6 weeks before the last frost and transplant seedlings outdoors once they have developed a few sets of true leaves.

If planting seedlings, dig holes slightly larger than the root balls and place the seedlings in the holes, spacing them according to the mature size of the Cosmos variety you're planting. Backfill the holes with soil and gently firm the soil around the base of the plants. Water thoroughly after planting to help settle the soil and encourage root establishment.

Keep the soil consistently moist but not waterlogged while the Cosmos plants are establishing themselves. Once they are established, they are relatively drought-tolerant and only need occasional watering during dry spells.

Cosmos plants are low-maintenance and generally do not require fertilization. However, you can incorporate a balanced fertilizer into the soil before planting or provide a light application of fertilizer during the growing season if desired.

Deadhead spent flowers regularly to encourage continuous blooming throughout the season and to prevent the plants from self-seeding excessively, especially if you want to control their spread in your garden.

How long do Cosmos Plants take to grow

Cosmos plants (Cosmos bipinnatus and Cosmos sulphureus) typically take about 7 to 10 days to germinate under optimal conditions. From the time of germination, they usually take around 60 to 90 days to reach full maturity and start blooming. Here’s a more detailed timeline:

1. Germination: 7-10 days after planting the seeds.
2. Seedling Stage: 2-3 weeks after germination.
3. Vegetative Growth: 4-6 weeks after the seedling stage.
4. Flowering: Generally starts 7-10 weeks after germination and continues throughout the growing season.

Cosmos plants are known for their fast growth and long blooming period, making them a popular choice for gardeners who want quick and continuous color in their gardens.

Why Grow Cosmos Plants?

Growing Cosmos plants offers several benefits, making them a popular choice for gardeners. Here are some key reasons to grow Cosmos:

1. Long Blooming Period: Cosmos plants bloom continuously from early summer until the first frost, providing extended color and beauty to gardens.
2. Easy to Grow: They are low-maintenance plants that thrive in various soil conditions and require minimal care once established. This makes them suitable for beginner gardeners.
3. Attract Pollinators: Cosmos flowers attract beneficial insects such as bees, butterflies, and other pollinators, supporting a healthy garden ecosystem.
4. Drought Tolerant: Once established, Cosmos plants are quite drought-tolerant, making them ideal for gardens in areas with limited water availability.
5. Versatility: Cosmos can be grown in garden beds, borders, and containers. They also make excellent cut flowers for arrangements due to their long stems and vibrant colors.
6. Variety of Colors and Sizes: Cosmos come in a wide range of colors (white, pink, purple, orange, yellow) and sizes, allowing for diverse garden designs and aesthetic preferences.
7. Self-Seeding: Cosmos plants often self-seed, meaning they can return year after year with minimal effort from the gardener.
8. Soil Improvement: As part of the Asteraceae family, Cosmos plants can help improve soil quality by attracting beneficial microbes and insects.
9. Pest Resistance: Cosmos are relatively resistant to common garden pests and diseases, reducing the need for chemical interventions.
10. Educational Value: They provide an excellent opportunity for children and novice gardeners to learn about plant growth, pollination, and garden ecosystems.

Growing Cosmos can enhance the beauty and health of a garden while offering an easy and rewarding gardening experience.

Where can you grow Cosmos Plants?

Cosmos plants can be strategically grown in various parts of your garden to maximize their beauty and benefits. Here are some specific locations within a garden where Cosmos plants can thrive:

Flower Beds and Borders:

• Background Plants: Due to their height (up to 6 feet for some varieties), Cosmos can be planted at the back of flower beds or borders, providing a colorful backdrop for shorter plants.
• Mixed Borders: They can be interspersed with other annuals and perennials to create a mixed border with continuous blooms.

Pollinator Gardens:

• Dedicated Pollinator Zones: Plant Cosmos in areas specifically designed to attract bees, butterflies, and other pollinators. Their vibrant flowers and abundant nectar are highly attractive to these beneficial insects.

Vegetable Gardens:

• Companion Planting: Cosmos can be planted near vegetable crops to attract pollinators, which can enhance the pollination of fruits and vegetables. They can also help deter pests.

Containers and Pots:

• Patios and Balconies: Grow Cosmos in large containers on patios or balconies to add height and color. Ensure the containers have good drainage and are large enough to support the plant’s root system.
• Entryways: Place pots of Cosmos near garden entryways or pathways for a welcoming display of flowers.

Cutting Gardens:

• Flower Arrangements: Plant a dedicated area with Cosmos for the purpose of cutting flowers. Their long stems and vibrant colors make them perfect for floral arrangements.

Wildflower Meadows:

• Naturalized Areas: Include Cosmos in wildflower mixes for meadows or naturalized areas. They can self-seed and return year after year, creating a dynamic and colorful display.

Sunny Spots:

• Maximize Sunlight: Choose the sunniest spots in your garden for planting Cosmos, as they need at least 6 to 8 hours of direct sunlight daily for optimal growth and blooming.

Edging and Pathways:

• Defining Spaces: Use shorter varieties of Cosmos to edge garden paths or define spaces within the garden. This can add a whimsical and colorful element to the garden layout.

Slopes and Hillsides:

• Erosion Control: Plant Cosmos on slopes and hillsides to help control erosion. Their root systems can help stabilize the soil while providing a beautiful display of flowers.

1. Filler Plants:

• Empty Spaces: Use Cosmos as filler plants in any empty spaces or gaps within your garden to ensure continuous color and coverage throughout the growing season.

By planting Cosmos in these various locations, you can take full advantage of their beauty, height, and benefits to create a vibrant and dynamic garden space.

Why Buy Cosmos Plants from Marshalls?

• Our customers are supported by a team of experts dedicated to providing valuable advice. You can also use our growing guides, backed by 70 years of experience, to get the best results from your Cosmos and other plants.
• You can contact us six days a week – including bank holidays – to discuss our products and services or to chat about all things gardening.
• We pride ourselves on offering fast delivery on all orders, with any 'in stock' plants and seeds sent out within three working days. We're green-fingered in more ways than one, too, thanks to our fully recyclable packaging.
• We won second place at the 2022 Great British Growing Awards for Best Online Retailer.
• Thousands of five-star reviews on Trustpilot and a 100% satisfaction guarantee on all our products show that we're a company you can trust.