How to Grow Cosmos Flowers

About Growing Cosmos Annuals in Your Home Flower Garden

Of all of the plants in the Cosmos, this one is destined to become one of your favorites. If you are a new gardener, growing Cosmos flowers is a great plant to start with. Fast-growing, there is little that can go wrong when growing this tall plant. Annual Cosmos plants are native to Central America and Mexico. They grow quickly to a height of 4-5 feet. Brightly colored single or double flowers in Sow Cosmos seeds directly into the garden just before the last frost in your area. The plant’s even and orderly petals led to its name, coming from the Greek word “kosmos,” which means “ordered universe in harmony.”

Cosmos plants look great at the back of the garden and in informal arrangements. They will reward you will colorful blooms all season long. So, grow them where they are readily visible from the windows of your house. Or, strategically place them along sidewalks where passersby will smile as they gaze upon them.

Our Favorite Cosmo: The hilarious Cosmo Kramer on the television sitcom Seinfeld (1989 – 1998). He came into our living rooms weekly and made us roar with laughter over his crazy antics.

Cosmos Plant Specifications

Flower colors: Colors include shades of chocolate, magenta, orange, pink, red, white, and yellow.

Flowers Blooms: Summer through Fall. See more information on the seed packet you selected.

Light Requirements: Full sunlight.

Ideal Soil pH: 5.0 – 8.0.

Hardiness Zone: 2 – 11.

Toxicity: Non-toxic.

Deer Resistant? Yes, somewhat. Deer will eat the plant if food is scarce in the area.

Number of Species: 30

Native To: Mexico, Central America, and the northern portion of South America.

Plant Type: Annual.

Botanical Name: Cosmos

Popular Varieties: Bright Lights, Sea Shells Mixture, Sensation Picotee

Are Cosmos Plants Edible?

Some varieties… Yes. Try Cosmos Suphureus or Cosmos Caudatas.

Some varieties… No. Avoid Cosmos Bippinatus and Cosmos Atrosanguineus..

The bottom is to know the varieties you have before you decide to chow down on.

For edible varieties, the petals and flowers can be eaten. They have a slightly tangy taste. The flowers are a great garnish. Use the flowers to decorate cakes, cookies, and other desserts. The petals add flavor to salads, soups, and stews.

Medicinal Uses for Cosmos Plants

Herbalists love the cosmos plants for its many medicinal benefits. The plant offers anti-bacterial, anti-diabetic, anti-inflammatory, and Antiviral properties. That covers treatment for a lot of ailments and medical conditions.

Here are some of the medicinal uses:

Use it to treat jaundice.
Treatment for malaria.
It lowers fevers.
Use it to fight infections.
Cosmos relieves some skin problems.
It strengthens bones.

Plant Light Requirements

Grow annual Cosmos plants in full sunlight. Ideally, locate them where they receive bright, direct sunlight all day long. The plants are thin and fern-like. Insufficient light causes them to grow even thinner, making them very susceptible to strong winds.

Also, insufficient light results in fewer flowers.

Cosmos Plant Propagation

The plants are grown from large seeds, making them easy to handle and to plant. Cosmos seeds germinate quickly and never stop from there, normally growing four to five feet in a season. Sow Cosmos seeds directly into the garden just before the last frost in your area. Cover seeds lightly with fine garden soil or seed-starting soil.

You can also start the plants indoors for transplanting after all danger of frost has past. Start cosmos seeds indoors in seed starting trays six to eight weeks before the last frost in your area.

For good germination, it is important to keep the soil moist while germinating. You do not need to water deeply as the seed and fine baby roots are just below the surface. However, if the weather and soil are dry, they may need frequent daily watering

While most varieties are annuals, there are perennial varieties. Perennial varieties are Rhizomes and can also be propagated by division.

Days to Germination: 7 – 10 days.

Final Plant Spacing: Space plants 12 inches apart and thin to 18 inches.

How to Grow Cosmos Flower Plants

Cosmos plants need full sun for optimal growth and plant health. Select a planting location where the plants receive both full sun and a little protection from strong winds that can know over the slim plants. Ideally, plant them along the south side of your house, shed, or other building.

The plants do well in both average and poor soils. In poor soils, give them a boost by adding a healthy amount of compost into the ground at planting time.

Cosmos plants are tolerant of dry soil conditions. Water established plants as needed during extended periods of drought.

Add a general-purpose fertilizer once or twice during the growing season, especially if the soil is poor.

Keep plants well-weeded when they are young. They can be overshadowed and lose out to weeds until they are a foot or so tall. Then, apply a thick layer of mulch to keep weeds down and to help to retain soil moisture.

Once the flowers bloom, the plant will continue to produce flowers all the way to the first frost. Deadhead spent blooms to keep a neat and tidy appearance. However, if you plan on harvesting seed for next year, keep a few flowers on the plant.

Taller plants may require staking. However, this can be avoided if planted in an area protected from the wind.

Pruning Annual Cosmos Plants

Here’s another reason to grow this attractive and low-maintenance flowering plant: It requires almost no attention. And, that includes pruning. The only time a pruning shears will come near this plant is when a branch breaks. And, that’s not too frequent.

However, it is wise to deadhead spent blooms. This encourages the plant to produce even more brightly colored flowers.

More on Deadheading Blooms.

Insect and Plant Disease

Insects and disease problems are very rare for Cosmos. If problems occur, treat them early with organic or chemical insect repellents and fungicides as appropriate.

Plant Problems – Identify the causes and find the cures.