Mexican Aster | Cosmos bipinnatus

Also known as the Garden Cosmos, Mexican Aster or Cosmos bipinnatus is a medium-sized, half-hardy annual belonging to the Asteraceae family. However, they self-seed and reappear for several years. The flowers are large, broad and brightly coloured, sometimes with coloured tips, stripes and patterns. Native to Mexico and Central America, Mexican Aster are a garden favourite, appreciated for their vibrant colours, easy care and reduced day-length requirements, which makes them suitable for summer gardening in the northern hemisphere. Colors come in a variety of shades, white, yellow, rose, orange, purple and magenta, with occasional bicolor blooms. They attract butterflies and birds, making them a must-have in every garden, balcony or terrace.

How to Plant and Grow Mexican Aster

Mexican Aster are suited to both indoor and outdoor potting, though they will thrive better outdoors in mild climates and areas with long summers. Plant the seeds indoors in late winter or sow outdoors in the soil just after the last frost of spring, or 6-8 weeks before the last frost of winter. Plant them in a sunny location, preferably one that receives several hours of direct sunlight a day. For best results, Mexican Aster will need rich, well-drained soil and regular watering during dry spells. Use a granular fertilizer, such as a balanced blend of NPK, but avoid over-fertilizing. Staked if necessary, and pinch off the flowering heads once blooming has finished to promote more flowers the following year. Mexican Aster will flower from the summer through to early autumn and will attract a variety of wildlife. Keep an eye out for pests and diseases, such as powdery mildew, spider mites and aphids.

Meaning and Symbolism

Mexican Aster is adorned with bright and vibrant petals perfect for creating vibrant displays that never fail to delight. This flower is often used as a symbol of strong will, creativity, and happiness and is a common summer bouquet flower choice, its striking appearance and cheerfulness making it a popular choice. It is suggested that the name ‘Mexican Aster’ is derived from its Latin name, Cosmos bipinnatus – ‘bipinnatus’ meaning ‘two-winged’. The flower’s bright colors and abundant petals adds a pleasant touch of unexpected surprise, underlining its popularity in bouquets.

History, Mythology, and Religious Significance

Historically, Mexican Aster was a popular choice for adorning religious altars and was used for various medicinal and cosmetic purposes. Ancient Greek and Egyptian civilizations used it to adorn their tombs. These days, it is used as an ornament in annual flower beds, borders, rock gardens, containers and hanging baskets. Mexican Aster has a special place in Mexican mythology and is believed to possess strong healing powers. It is a popular choice among worshippers in many religions, particularly Hinduism and Buddhism which consider it to be a symbol of luck and wealth.

Flower Varieties and Their Defining Characteristics

There are several varieties of Mexican Aster, each with its own distinct characteristics. Cosmos sulphureus, or the sulphur-coloured cosmos, features daisy-like flowers with multiple yellow petals. Cosmos bipinnatus, or the double-winged cosmos, produces golden-orange-red petals and is perfect for a cottage garden. The Cosmos ‘Dazzler Mixed’ variety of Mexican Aster is one of the most celebrated for its unique colour combinations. This variety stands out for its multi-colored flowers and colorful center. All varieties have tall sturdy stems, lush green foliage and a delightfully sweet scent.

How to Pot and Repot Mexican Aster

Mexican Aster is best propagated through seeds at the start of the warm season in well-draining soil. Using a pair of scissors, evenly distribute the Mexican Aster seeds throughout the soil, burying them to a depth of 1-2 centimetres. Water the soil and keep moist until the seeds sprout. Once they appear, thin the seedlings out so they are 20-25 centimetres apart. When they are around 10-15 centimetres in height, transplant to a larger pot of compost or soil. To improve drainage, potting or planting into soils which contain compost or well-rotted animal manure is advantageous.

How to Prune

In order to prolong the blooming period, it’s important to prune Mexican Aster regularly. Prune stems and remove wilted or dead flowers to improve their appearance, encourage healthy plant growth and flowering, and also to prevent self-seedings. To do this, use a pair of sharp secateurs to cut the stalk of a flower along its full length, ensuring that you make the cut just above a leaf node. Aim to conduct this task on a regular basis until the end of the flowering season.

How to Propagate

Mexican Aster can be propagated through seeds, cuttings or division. Starting Mexican Aster from seed is the most popular method, with this plant thriving in a range of temperatures, between 10-20 degrees Celsius. Soak the seeds overnight in warm water before sowing the seeds thinly into trays filled with moist compost mix and covering with a thin layer of soil. Leave the tray in a warm area, such as a greenhouse or warm windowsill, and keep the soil moist but not wet. Mexican Aster can also be propagated by gently separating overgrown clumps, then planting the divisions in separate pots. Cuttings taken from an existing Mexican Aster can also be planted directly into pots of compost.

Common Pests and Diseases

Mexican Aster is generally robust and is generally fairly resistant to diseases, however some pests and diseases can occur. Mildew, aphids, and caterpillars may attack the plant. The most common disease to affect Mexican Aster is powdery mildew. Signs of this disease include discoloration and a white fuzzy powder. Mexican Aster can also suffer from root rot, caused by overwatering, which can be identified by yellowing and wilting of foliage. To prevent these problems, be sure to regularly check your plants for signs of disease and maintain a proper watering frequency.

Three Frequently Asked Questions About Cosmos Bipinnatus

• What type of flower is Mexican Aster?
  Mexican Aster is a half-hardy annual belonging to the Asteraceae family.
• How can I make Mexican Aster last longer in a vase?
  To make Mexican Aster last longer in a vase, trim the stem each day and change the water. Make sure to cut the stem at an angle to help the flower absorb more water.
• Are Mexican Aster deer resistant?
  Yes, Mexican Aster are generally considered deer resistant.

A Table Fact Sheet, with Data

Mexican Aster	Cosmos bipinnatus
Family	Asteraceae
Plant Type	Half-Hardy Annual
Mature Size	Up to 90 cm tall and 30 cm wide
Sun Exposure	Full Sun
Soil Type	Moist, well-drained, sandy soil
Soil pH	6.8 – 7.8
Bloom Time	Summer through to early autumn
Flower Color	White, yellow, rose, orange, purple and magenta, with occasional bicolor blooms
Hardiness Zones	3 – 10
Native Area	Mexico and Central America