How to Grow Mexican Aster Flowers (Cosmos bipinnatus)

growing Mexican Asters

by Jennifer Poindexter

Are you searching for a subtle way to add charm to your home?

Have you considered growing Mexican asters? These beautiful flowers produce classic blooms in a variety of colors.

It’s a sure way to add a welcoming touch to your landscape without overdoing things. If you’d like to learn how to incorporate this classic beauty around your home, you’re in the right place.

I’m going to walk you through finding the perfect growing location as well as teach you how to care for and even protect this gorgeous flower.

Here’s what you should know to incorporate Mexican aster to your home:

Growing Conditions for Mexican Aster

Mexican asters are a great choice for virtually any garden. In fact, this plant can grow in planting zones one through ten.

However, it’s only a perennial in frost-free zones. In other locations, this flower will grow as an annual only.

Yet, they reseed easily. Therefore, they may come back on their own each year, even in cooler growing locations.

Mexican aster will bloom in the summer and fall months. It produces classic, daisy-like blooms in colors ranging from red, orange, and even yellow. It’s also a great choice for growing locations where not much else wants to grow.

The only real specification this flower has is full sun. Otherwise, even if the soil quality is poor, the plant should still prosper. It’s also important that the soil drains adequately.

If water can reach the roots of the plant and drain away quickly, you should be good to go. The main thing is that the plant isn’t left in an oversaturated state as this can lead to fungal issues as the growing season progresses.

You should also consider the height of this plant when picking a growing location. Mexican asters can grow to be anywhere from three to six feet tall. Their height alone makes them a wonderful choice for edging or for use as a backdrop to smaller plants.

It’s also great at attracting pollinators. This is good news if growing Mexican aster in or near a garden.

However, this might not be the best choice for growing in a high traffic area. Take these tips into consideration as you pick the best spot to plant Mexican aster around your home.

How to Plant Mexican Aster

By this point, you should have an ideal location chosen to plant Mexican aster. It’ll be up to you to decide if you’d like to start this flower indoors or outdoors.

If you want a jumpstart on the growing season, start Mexican aster indoors six weeks prior to the final frost date of spring.

Fill a seed tray with adequately draining soil. Place two seeds per cell of the growing tray. This serves as an insurance policy if one of the seeds fails to germinate.

Lightly cover the seeds with soil and place them in a bright location or under a grow light. Mist the soil with a spray bottle to water the seeds.

You want the soil to stay consistently moist throughout the germination process without becoming overly saturated.

Using a squirt bottle helps keep the balance. It’s also a good idea to cover the growing tray with plastic wrap as this provides a greenhouse effect for the seeds.

Your Mexican aster seeds should germinate within ten days. Ensure you keep the soil warm, and evenly damp, to avoid damping off.

This can occur when seedlings are grown in overly saturated and cold soil. There’s no reversing it, so ensure you follow the steps above to produce strong seedlings. Move the seedlings to their permanent growing location once they’ve formed true leaves and all threat of frost is over.

The other option for growing Mexican aster is to sow the seeds directly outdoors. Pick a growing location with all the specifications mentioned above.

Prepare the soil for seeding by tilling the ground and ensuring the dirt drains adequately. When ready, cast the seed to lightly cover the growing area.

Be sure the temperatures are remaining consistently between 70- and 80-degrees Fahrenheit. This will give the plants the greatest chance of surviving and ultimately thriving under your care.

The seeds should be planted at a depth that’s approximately 1/16 of an inch deep. Lightly cover the seeds using a rake, and wait ten days for germination to occur.

When transplanting outdoors, or once the directly sowed seeds have sprouted, ensure there’s one foot of space between each plant. This will provide proper spacing to keep the plants healthy as they mature.

Once your plants are in the ground and become established, it’s time to move on in the growing process to ensure you know how to care for mature Mexican aster plants.

Caring for Mexican Aster

Mexican aster is a low-maintenance flower. Once you learn how to water the plant properly, deadhead the flowers at the appropriate time, and support the stems you’ve learned all you need to keep this plant thriving.

To start, it’s best to deep water this flower though it’s a drought tolerant plant. Deep watering means you’ll water the plant for a longer period of time fewer days of the week.

This ensures that water reaches the roots of the plant during the initial watering session. However, it also saturates the ground surrounding the plant.

Over time, the Mexican asters will require more water and dig deeper into the ground to receive the moisture needed. This forms stronger root systems and typically equates to healthier plants.

You’ll know it’s time to add more water to the plants by testing the soil. Stick your finger into the dirt and when you feel moisture at your second knuckle, you’ll know the flowers don’t need any more water.

Test the soil again a day or so later, and if it’s dry to your second knuckle it’s time to have another deep watering session.

The next thing you must do is remove dead blooms. This is referred to as deadheading. Not only does this make the plant look better, but it also helps redirect its energy to the younger portions.

This could keep your flowers looking younger and more vibrant for a little longer into the growing season.

The final thing you’ll need to do to care for Mexican aster is to stake the stems. If your asters are becoming tall, you don’t want the blooms to become too heavy and break the stems.

Therefore, it’s a good idea to add a little extra support to keep your blooms standing tall and upright the entire bloom cycle.

Provide these small amounts of care to your Mexican asters, and you should have gorgeous flowers blooming around your home with only a little extra effort on your part.

Garden Pests and Diseases Which Could Impact Mexican Aster

Most plants face threats in their growing locations. They can come in the form of pests and diseases. Mexican aster is no exception to this rule.

The most common diseases which threaten this type of plant are aster yellows, rust, and powdery mildew. Aster yellows is carried from plant to plant by leafhoppers.

This disease can cause the foliage of the plant to become yellow and stunted. There’s no cure for this disease. Once a plant is infected, you should remove it from the growing location and destroy it to avoid other plants from becoming infected.

Rust and powdery mildew can be treated with a fungicide. However, prevention is the best method when dealing with a disease.

When facing fungal issues, it’s best to ensure you don’t create an environment for fungus to grow. Therefore, plant Mexican aster where it receives ample sunlight and in soil that drains well.

Also, ensure there’s plenty of space between each plant. By providing these conditions, you’re avoiding cold and excessively damp soil which is the perfect breeding ground for fungal disease.

Adequate spacing ensures that there’s proper airflow between the plants to keep the soil and foliage dry.

The other issues you might face, when growing Mexican asters, are pests. Leafhoppers, aphids, spider mites, thrips, whiteflies, scales, and weevils all threaten this flower. Each of these pests can be treated using insecticidal soap.

Read the instructions on the insecticide to ensure you apply the appropriate amounts at the right times. You should also check to ensure the insecticide treats all the pests you’re battling.

By catching issues early, you stand a greater chance at helping your plants survive whatever they might come up against.

You now know the appropriate information to try your hand at growing Mexican asters around your home or garden. These flowers can be the classic but vibrant addition you’ve been seeking. 

Yet, they’re also low maintenance. Take these tips and start adding natural beauty around your home for curb appeal and for your enjoyment.

Learn More About Mexican Aster

Mexican Asters growing in garden with text overlay How to Grow Mexican Aster Flowers

The post How to Grow Mexican Aster Flowers (Cosmos bipinnatus) appeared first on Gardening Channel.



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