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Will chocolate cosmos grow in shade?

Welcome! As your SEO writer assistant, let me provide some introductory information before diving into the details about growing chocolate cosmos in shaded conditions.

About Chocolate Cosmos

The chocolate cosmos (Cosmos atrosanguineus) is a stunning flower prized by gardeners for its rich brown or maroon colored blooms that smell faintly of chocolate. Native to Mexico, this tender perennial is notoriously difficult to grow. However, with the right care and environment, it can thrive both in the garden and as a potted plant.

Key Facts About Chocolate Cosmos:

  • Plant type: Tender perennial, grown as an annual in most climates
  • Native to: Mexico
  • Hardiness: Zones 8-10
  • Mature size: Up to 3 feet tall and 2 feet wide
  • Bloom time: Summer to fall
  • Flower color: Deep red, brown, or maroon
  • Sun exposure: Full sun ideal, partial shade possible
  • Soil: Rich, well-draining soil
  • Water: Moderate, keep moist but not soaked

Chocolate Cosmos Light Requirements

When it comes to sunlight, chocolate cosmos prefer full sun conditions. This means getting at least 6 hours of direct sunlight per day. With enough light, the flowers will bloom prolifically and take on their signature deep, rich coloring.

That being said, chocolate cosmos can adapt to partial shade. Shade levels up to about 50% are often still sufficient for good growth and flowering. However, with less light exposure, the following may occur:

  • Fewer blooms
  • Paler flower color
  • Lankier growth habit
  • Increased susceptibility to disease

If planting chocolate cosmos in a shaded area, choose a spot that receives morning sun or dappled sunlight filtered through a thin tree canopy. This provides some direct sunlight while minimizing the hottest afternoon rays. Morning sun often contains higher levels of the red and blue light wavelengths that drive flowering.

Minimum Sun Requirements

Most experts recommend chocolate cosmos receive at least 4-6 hours of sunlight per day to produce an acceptable number of blooms. With less light than this, flowering and performance will be quite poor.

Optimizing Growth in Shade

When growing chocolate cosmos in shade, take the following steps to help optimize growth and flowering:

Choose the Right Spot

  • Select a location that receives morning sun or dappled sun filtered through thin trees.
  • Avoid thick shade created by bushes, walls, or dense trees.
  • Plant on the south or east side of structures.
  • Move potted plants to the brightest location possible.

Improve Light Exposure

  • Prune back overhanging branches to open up the area.
  • Remove competing plants that may block sunlight.
  • Use reflective mulch around plants to bounce light back up.
  • Supplement with grow lights if shade is unavoidable.

Prepare the Soil

  • Amend soil with 2-3 inches of compost to improve drainage and nutrition.
  • Add organic material like compost each season.
  • Mulch around plants to retain soil moisture and regulate temperatures.

Provide Exceptional Care

  • Water thoroughly when top few inches of soil become dry.
  • Feed monthly with a balanced liquid fertilizer.
  • Remove spent blooms to encourage more flowering.
  • Stake plants and prune as needed to improve air circulation.

Growing From Seed vs. Starts

Chocolate cosmos can be planted by seed or from nursery starts. Here is a comparison:

Seeds Nursery Starts
  • Less expensive
  • More challenging to grow
  • Can take 10-12 weeks from sowing to bloom
  • Lower germination rates
  • Enjoyable for experienced gardeners
  • More expensive
  • Easier, more reliable growth
  • Bloom first season if planted early enough
  • No germination issues
  • Best for beginners

With either method, be sure to plant chocolate cosmos at the recommended spacing for your zone. This gives them room to reach mature size.

Companion Plants

Chocolate cosmos pair nicely with other shade-tolerant plants. Combining them with the following companions can create an attractive shaded garden display:

Shade Annuals

  • Begonias
  • Impatiens
  • Coleus
  • Wax begonias
  • Browallia
  • Persian shield

Shade Perennials

  • Astilbe
  • Coral bells
  • Hostas
  • Ferns
  • Hellebores
  • Epimediums
  • Heucheras

Secondary Accents

  • Japanese maples
  • Hydrangeas
  • Azaleas
  • Impatiens
  • Caladiums
  • Ferns

Repeating chocolate cosmos throughout the planting and using complementary colors will give a cohesive look. Maintain proper spacing between plants and prune when needed to keep an orderly appearance.

Special Considerations for Pots

Container gardening opens up possibilities for growing chocolate cosmos in small spaces or movable planters. Follow these tips for successfully growing in pots:

  • Use a 14-16 inch diameter container with drainage holes.
  • Fill with a premium potting mix, not garden soil.
  • Add slow-release fertilizer to the soil before planting.
  • Situate the container in the brightest spot possible.
  • Move the pot around to follow the sunlight as needed.
  • Water when the top inch of soil becomes dry.
  • Replant each year into fresh potting mix.

With excellent care, chocolate cosmos grown in containers can thrive and flower despite being in shade. Hanging baskets are another fun option for displaying these beautiful blooms in shaded areas.

Extending the Blooming Season

Chocolate cosmos bloom from summer through fall. To maximize the length of bloom time in shade, do the following:

  • Start early indoors: Begin seeds or cuttings 2-3 months before your last frost date.
  • Succession sow: Plant small batches of seeds every 2-3 weeks to stagger blooming.
  • Deadhead flowers: Remove spent blooms to encourage more flowering.
  • Fertilize regularly: Feed plants monthly to nurture growth and blooms.
  • Provide supplemental light: Use grow lights or reflective mulch to boost sunlight levels.

With attentive care, you can enjoy these beautiful blooms for 3-4 months rather than just a few short weeks. Planting early, deadheading, and fertilizing are key to maximizing bloom time in shaded gardens.

Overwintering Chocolate Cosmos

In zones 8-10, established plants can be overwintered with protection. In colder zones, chocolate cosmos must be grown as annuals and replanted each spring. To successfully overwinter plants:

  • Cut plants back by 2/3 in fall and trim away dead growth.
  • Cover beds with 4-6 inches of shredded bark or leaf mulch.
  • Add an insulating layer like straw or burlap over the mulch.
  • Consider constructing mini hoop houses over plants for added protection.
  • Remove insulation in spring once the risk of frost has passed.

With adequate winter protection, the rhizomes should survive and regrow the following season. Supply supplemental heat during cold spells for the best overwintering success.

Troubleshooting Common Problems

Chocolate cosmos can be prone to issues when grown in too much shade. Here are some common problems and solutions:

Problem Cause Solution
Few or no flowers Insufficient sunlight Increase sunlight levels or provide supplemental lighting
Tall, leggy growth Reaching for sunlight Pinch or prune plants to encourage bushy growth
Leaf spots Fungal disease Improve air circulation and avoid wetting foliage
Root rot Excess moisture Plant in well-draining soil, allow soil to dry between waterings

Providing optimal care by fertilizing, pruning, and monitoring moisture levels will help prevent many issues. Boosting sunlight levels is key to growing lush, healthy chocolate cosmos in shadier conditions.

Frequently Asked Questions

Can chocolate cosmos handle full shade?

No, full shade is too dark for chocolate cosmos. They may survive, but will produce few if any flowers. A minimum of 4 hours of direct sun per day is recommended.

Should chocolate cosmos be potted or planted in the ground?

Either way can work, just ensure the soil is rich in organic matter. Amend garden beds with compost and use quality potting mixes for containers. Provide adequate drainage for healthy roots.

What are good companion plants for chocolate cosmos?

Some great shade-loving companions include begonias, impatiens, astilbe, coral bells, hostas, and ferns. Choose plants with contrasting colors and textures for visual interest.

Is chocolate cosmos hardy in zone 7?

Unfortunately no, chocolate cosmos is only reliably hardy through zone 8. Anything colder will require overwintering indoors or treating it as an annual.

Should I cut back chocolate cosmos in fall?

Yes, cut plants back by 2/3 and trim away dead growth in fall to prep them for winter. Leave the rest of the stems and roots intact.


While chocolate cosmos prefer full sun, they can adapt to partial shade conditions given proper care. Choose an appropriately bright spot, amend the soil, be diligent about watering and fertilizing, and take steps to maximize sunlight levels. With attention to its needs, the charming chocolate cosmos can thrive even in dappled or morning sun environments.