The chocolate cosmos (Cosmos atrosanguineus) is a captivating and unusual flowering plant that enchants gardeners and plant enthusiasts with its distinctive dark reddish-brown, almost black blooms that exude a tantalizing chocolate scent. Native to the meadows of Mexico, this perennial member of the Asteraceae family is celebrated not only for its unique and exotic appearance but also for its intriguing olfactory appeal.
First discovered in the 19th century, the chocolate cosmos stands out in the plant world for its rich, velvety flowers, which can grow up to 3-4 cm in diameter. Chocolate cosmos typically grows to a height of 40-60 cm (16-24 inches). These striking blossoms bloom in the warmth of summer and early autumn, adding a touch of drama and sophistication to any garden setting. Despite its ornamental beauty, the chocolate cosmos faces conservation challenges, as it is considered extinct in the wild and survives solely through horticultural cultivation.
Cultivating chocolate cosmos involves providing well-drained soil, ample sunlight, and regular watering. Gardeners value this plant not only for its aesthetic qualities but also for its delightful chocolate aroma, which intensifies in the heat of the day, creating a sensory experience that is as pleasing to the nose as it is to the eyes.
Today, the chocolate cosmos is cherished in ornamental gardens and as a cut flower in floral arrangements, where its dark, alluring blooms and sweet fragrance can be fully appreciated. Through dedicated cultivation and propagation efforts, this botanical treasure continues to thrive, captivating all who encounter its enchanting allure.
Sunlight Requirement of chocolate Cosmos
The chocolate cosmos thrives best in full sun. This means the plant should ideally receive at least 6-8 hours of direct sunlight each day to ensure healthy growth and abundant blooming. While it prefers full sun, chocolate cosmos can tolerate partial shade, especially in regions with very hot climates. However, too much shade can result in fewer flowers and weaker plants.
Soil Requirement
Chocolate cosmos requires well-drained soil to prevent waterlogging, which can lead to root rot. Ensuring good drainage is essential for the plant’s health. The soil should be moderately fertile. While the plant does not need extremely rich soil, it benefits from the nutrients present in moderately fertile environments. A sandy loam or loamy soil is ideal. These soil types offer the right balance of drainage and nutrient retention. The chocolate cosmos prefers a neutral to slightly alkaline soil pH, typically in the range of 6.0 to 7.5.
Temperature and Humidity Requirement
Chocolate cosmos prefers warm temperatures and thrives best in areas where the temperature ranges between 70°F to 85°F (21°C to 29°C) during the growing season. The plant is sensitive to frost and should be protected from freezing temperatures. In regions with cold winters, it’s best to dig up the tubers and store them in a cool, dry place until the threat of frost has passed. Chocolate cosmos prefers moderate humidity levels.
Winter Storage: If grown in colder climates, tubers should be stored at a temperature of around 40°F to 50°F (4°C to 10°C) to prevent them from freezing and to ensure they remain viable for replanting in the spring.
Propagation of Chocolate Cosmos Flowers
Propagation of chocolate cosmos (Cosmos atrosanguineus) is typically done through division or cuttings, as the seeds of this plant are generally sterile. Here are the steps for both methods:
Propagation by Division
In late fall, after the plant has finished blooming and before the first frost, carefully dig up the tubers.
Use a clean, sharp knife to divide the tubers. Ensure that each division has at least one growing point or “eye.”
Allow the divided tubers to dry for a day or two in a cool, dry place to form a callous over the cuts. Store them in slightly damp peat moss or vermiculite in a cool, frost-free place (around 40°F to 50°F or 4°C to 10°C) over winter.
In spring, once the risk of frost has passed, plant the tubers in well-drained soil with the growing point just below the soil surface.
Plant the tubers with the growing point just below the soil surface. Space them about 12-18 inches (30-45 cm) apart.
Propagation by Cuttings
In late spring or early summer, take 4-6 inch (10-15 cm) cuttings from healthy, non-flowering stems. Cut just below a node (the point where leaves attach to the stem).
Remove the lower leaves from the bottom half of the cutting. Dip the cut end in rooting hormone to promote root development.
Insert the cuttings into a pot filled with a well-draining potting mix, such as a mixture of perlite and peat moss.
Cover the pot with a clear plastic bag or place it in a propagator to maintain high humidity. Ensure the cuttings are in a warm, bright spot out of direct sunlight.
Keep the soil moist but not waterlogged. Roots should develop in 4-6 weeks. Once the cuttings are well-rooted, transplant them into individual pots or directly into the garden.
Water Requirement
During the active growing period in spring and summer, water the plant regularly to keep the soil evenly moist. This typically means watering once or twice a week, depending on the weather conditions and soil type. Reduce watering in the fall as the plant enters dormancy and stop watering entirely during winter if the tubers are stored.
Fertilizer Requirement
Apply a balanced fertilizer at the beginning of the growing season to support initial growth. Use a balanced, all-purpose fertilizer with an N-P-K ratio (nitrogen, phosphorus, potassium) such as 10-10-10 or 20-20-20. A second application in mid-summer can promote continued blooming and overall plant health. Organic options like compost or well-rotted manure can also be beneficial.
Winter Care of Chocolate Cosmos Flowers
Winter care is crucial for chocolate cosmos to ensure the plant survives the cold season and regrows the following spring.
Begin preparing the plant for winter care in the fall, before the first frost hits.
Cut back the stems and foliage to a few inches above the ground. This helps the plant focus energy on the tubers.
Gently lift the tubers out of the soil. Be cautious not to break or bruise them. Use a garden fork or spade to carefully dig around the base of the plant to avoid damaging the tubers.
Brush off excess soil from the tubers. Avoid washing them, as excess moisture can lead to rot during storage.
Allow the tubers to air dry in a cool, dry place for a day or two to let the cut surfaces heal and form a callous.
Place the dried tubers in a container filled with slightly damp peat moss, sand, or vermiculite. This medium helps maintain a stable moisture level around the tubers.
Use a breathable container like a cardboard box or paper bag to allow for air circulation.
Store the container in a cool, dry place with temperatures around 40°F to 50°F (4°C to 10°C). Avoid areas that are too warm or subject to freezing temperatures.
Periodically check the tubers for signs of rot or dehydration. If the storage medium feels too dry, lightly mist it with water. If tubers show signs of rot, remove the affected tubers immediately.
Replant the tubers in the garden after the last frost has passed and the soil has warmed up.
Problems While Growing Chocolate cosmos
Growing chocolate cosmos can present several challenges. Here are common problems you might encounter and how to address them:
Pests
Aphids: These small insects suck sap from the plant, causing yellowing leaves and distorted growth. Use insecticidal soap or neem oil to control aphids. Introducing beneficial insects like ladybugs can also help.
Spider Mites: These tiny pests cause stippling and discoloration of leaves. Increase humidity around the plants and use insecticidal soap or neem oil.
Slugs and Snails: These pests can chew on the leaves and stems. Use slug and snail bait or traps. Removing debris and maintaining a dry area around the base of the plant can also help deter them.
Diseases
Powdery Mildew: This fungal disease appears as a white, powdery coating on the leaves. Improve air circulation around the plants by spacing them properly. Apply fungicides if necessary and avoid overhead watering.
Root Rot: Caused by waterlogged soil, this can lead to yellowing leaves and wilting. Ensure well-drained soil and avoid overwatering. Plant in raised beds or amend soil with organic matter to improve drainage.
Botrytis Blight (Gray Mold): This appears as gray, fuzzy mold on leaves, stems, and flowers, especially in wet conditions. Remove affected parts of the plant and dispose of them. Ensure good air circulation and avoid overhead watering. Apply fungicides if necessary.
Cultural Problems
Poor Flowering: This can be due to insufficient sunlight, poor soil nutrition, or excessive nitrogen, which promotes foliage growth over flowering. Ensure the plant receives at least 6-8 hours of direct sunlight. Use a balanced fertilizer and avoid over-fertilizing with nitrogen.
Leggy Growth: Often caused by insufficient light. Ensure the plant is in a location with adequate sunlight. Pinch back growing tips to encourage bushier growth.
Frost Damage: Chocolate cosmos is sensitive to frost. Protect the plant from frost by mulching or using frost covers. Dig up tubers before the first frost and store them indoors.
