Cosmo Flowers

Why Grow Cosmos?

Cosmos are easy-to-grow annual flowers known for their airy foliage and daisy-like blooms.
They thrive in poor soil and require minimal care—perfect for pollinator gardens, cottage gardens and cut flower arrangements.
Deer and Bunnies don't like them. I don't have deer, but I do have lots of bunnies.

Growing Calendar (Northern Hemisphere)

Preferred Soil Conditions for Cosmos:

1. • Type:   Well-draining, light and moderately fertile soil.
2. • Texture:   Sandy or loamy soils are ideal.
3. • Nutrients:   Cosmos grow best in soil that is not too rich in nutrients—overly fertile soil can lead to lush foliage with fewer flowers.

Preferred pH Range:

1. • pH: 6.0 to 7.0 (slightly acidic to neutral)

Additional Tips:

1. • Avoid heavy clay or waterlogged soils.
2. • Do not over-fertilize, especially with nitrogen-rich fertilizers.
3. • Adding compost can help with drainage and moderate fertility.

Self-seeding magic:

1. Let some flowers go to seed in the fall and they'll naturally reseed for next year.

Succession Planting Tips:

1. • Every 3-4 weeks: Sow a new batch to ensure continuous blooms from summer to fall.
2. • Thin seedlings to 9-12 inches apart for best airflow and bloom size.
3. • Choose a mix of early- and late-blooming varieties for diversity.

Cosmos attract pollinators and beneficial insects,
making them excellent companions in the garden.

Try pairing Cosmos with:

Vegetables:   Tomatoes, peppers, squash (for pollination).
Flowers:   Zinnias, marigolds, nasturtiums, sunflowers.
Herbs:   Dill, basil, and coriander (all attract beneficial insects).
Avoid planting too close to very vigorous growers that may shade them out.
Companion planting:   Pair cosmos with coneflowers, black-eyed Susans, or goat's beard for a stunning display.

Flower Arranging Tips:

Cut cosmos when buds are just beginning to open for longer vase life.
Strip lower leaves to avoid rot in water.
Combine with airy fillers like Queen Anne's lace and bold blooms like dahlias or sunflowers.
Use floral preservative to extend vase life.
Look-out for dropping pollen.

Vase Life:

Typical lifespan: 5-7 days
Cosmos are prone to drooping—cut stems early in the morning and immediately hydrate them.
Change water daily to keep blooms fresh.

Cosmos can have delicate, hollow stems that sometimes break—especially in windy spots or when the plant gets tall and leggy.

Here's how to prevent cosmos branches from breaking:

Protect from Wind:
Plant in a sheltered spot or use windbreak like fences, hedges, or even taller companion plants.
If your garden is exposed, stake taller varieties using bamboo canes or tomato cages.

Pinch Out Cosmos for Bushier Growth:

1. • When seedlings are 6-8 inches tall, pinch the top growth to encourage branching and sturdier stems.
2. • Pinching helps reduce leggy, top-heavy growth that breaks more easily.
3. • Use the Cosmos cuttings and start new Cosmos plants.

Avoid Over-Fertilizing:

1. • Too much nitrogen (like from lawn runoff or rich compost) can cause lush but weak stems.
2. • Cosmos prefer lean, well-draining soil—skip the fertilizer unless plants are stunted.

Water Deep, Not Often:

1. • Frequent shallow watering encourages weak, brittle stems.
2. • Water deeply and let soil dry between watering to build stronger roots and stems.

Remove Damaged Stems:

1. • If a branch breaks, cut it cleanly near the base to prevent disease.
2. • Damaged branches won't recover and can sap the plant's energy.

Cosmos - Interesting Facts:

• Self-seeding:   Cosmos readily reseed if left in place—great for low-maintenance gardens.
• Pollinator magnet:   Loved by bees, butterflies, and hoverflies.
• Varieties:   Includes Cosmos bipinnatus (tall, daisy-like) and Cosmos sulphureus (more compact, yellow/orange tones).
• Drought-tolerant:   Once established, cosmos are very water-wise.

How to Grow Cosmos in Containers (infographic)
Growing Cosmos in containers is a rewarding and low-maintenance way to enjoy their vibrant, daisy-like blooms even if you don't have garden space. Shorter varieties work well in pots, brightening up patios and balconies.

Why Grow Cosmos in Containers?

• Ideal for balconies, patios, or small gardens.
• Long blooming season:   early summer to frost.
• Attract pollinators:   bees, butterflies and hoverflies.
• Low maintenance and drought-tolerant.

Choosing the Right Container:

• Size:   At least 12 inches deep and 12 inches wide for dwarf varieties. For taller types (like Cosmos bipinnatus), choose 16-18 inches deep.
• Drainage:   Ensure the container has good drainage holes.
• Material:  Plastic, ceramic, or terracotta pots all work. Terracotta dries out faster.

Soil and Planting:

1. • Soil: Use a light, well-draining potting mix. Avoid rich soil—cosmos thrive in poor to average soil and bloom better.

Sowing and Planting:

1. start seeds indoors 4-6 weeks before the last frost and transplant them.
2. Thin to one plant per pot or space 6-8 inches apart in larger containers.

Light and Temperature:

• Sunlight:  Needs 6-8 hours of full sun daily.
• Prefers warm weather. Protect from frost.

Watering and Feeding:

Watering:
Keep soil lightly moist until germination.
Once established, water deeply but infrequently—let the top inch of soil dry out between waterings.

Fertilizing:
Avoid heavy feeding — too much nitrogen = more leaves, fewer flowers.
A balanced, diluted liquid fertilizer every 4-6 weeks is sufficient.

Pruning & Maintenance:

• Deadhead regularly to encourage continuous blooming.
• Pinch back young plants to promote bushier growth.
• Stake tall varieties in containers to prevent flopping.

Best Varieties for Containers:

1. • 'Sonata' Series - compact, 12-24 inches tall, comes in carmine, pink and white.
2. • 'Cosmic Orange' - bright orange blooms, compact and vibrant.
3. • 'Xanthos' - soft yellow, dwarf variety, great for pots.

Bonus Tips for Containers:

1. • Companion plant with marigolds, zinnias, or nasturtiums for colour and pollinators.
2. • Rotate containers every couple of days if sunlight is uneven.

Why Grow Cosmos? — FAQ

All about Seeds and Seedlings
Printable Seedpackets and Seedpacket Dividers
Chart for Seed Germination with light and without
All about Flowers