How to Plant, Grow, and Care for Mexican Sunflower

There are actually two species that qualify as Mexican sunflower, both of which are Tithonia species. Tithonia rotundifolia is also called the “red sunflower”, but Tithonia diversifolia has a slew of names ranging from “Japanese sunflower” to “tree marigold” or “Mexican tournesol”. 

Both share the common name Mexican sunflower, but the former is orange-to-red in color, and the latter is yellow. Each Mexican sunflower is so closely related that their care is identical. Both are native to Mexico. They’re both great shrubs for drawing in butterflies, and hummingbirds love them! 

Any master gardener will tell you Mexican sunflowers make a great addition to any butterfly garden as they are known for attracting many beneficial insects, including monarch butterflies. Grow Mexican sunflowers alongside milkweed (the monarch butterfly’s host plant), castor beans, flowers that look like sunflowers, and other butterfly-friendly species in order to provide them with an additional food source. 

Tithonia diversifolia is a little more widespread than Tithonia rotundifolia (common red sunflower), but both are common garden shrubs. To prevent confusion from here on out, we will discuss T. diversifolia. This easy shrub is in the Aster family and has flowers that resemble marigolds (which are also in the Aster family). 

In both cases, Mexican sunflower care is the same. Now, let’s talk about how to grow Mexican sunflowers!

What are Mexican Sunflowers?

Mexican sunflower (Tithonia diversifolia) are also known as tree marigold, Mexican tournesol, Japanese sunflower, nitobe chrysanthemum, or simply tithonia. Although Mexican sunflower is the most common name for this shrub, tree marigold seems like the most appropriate name. They can grow to be eight feet tall and resembles a small tree! And the flower more closely resembles that of marigolds rather than true sunflowers.

Native Area

As their name would suggest these flowers originate from Mexico and Central America. They are grown as annuals in most areas but can be grown as perennials in USDA zones 9-11. In warmer climates, they can be cut back to the woody growth in late fall/early winter and they will grow back in the spring. 

Characteristics

The tithonia flower can come in a variety of colors, but the most popular are shades of red, orange, and yellow. T. diversifolia is most often yellow. 

Growing Mexican sunflower is so easy that you might even do it by accident! They have the ability to set roots from any point on the stem, much like a tomato. This means that if one of these sunflowers falls to the ground it then has the ability to root itself and grow a new flower. It is this growth habit that has led to it being considered invasive in some areas. 

All that being said, because of its aggressive growth, it can be used as a source of biomass and used to add organic matter to other areas of your garden. When using them this way it is important to run the stalks through a chipper or chop them finely to avoid them spreading to an area where you don’t want them. This way you can grow your own fertilizer! 

Mexican sunflowers have been referred to as comfrey of the south, and pound for pound provide nutrients equivalent to chicken manure. For this reason, it has also been referred to as vegan manure. Because Mexican sunflower care is so minimal, you’ll have great success using this way.  

If you’re concerned about dedicating a large amount of vertical space to the Mexican sunflower, then never fear! There are also dwarf varieties that won’t grow as tall such as ‘Fiesta Del Sol’. These smaller shrubs don’t take up as much space and still offer beautiful cut flowers from the garden. 

Planting

Select a sunny location with well-draining soil, as this fast-growing shrub thrives in warm climates. Enrich the soil with compost and organic matter to grow them rapidly. Propagate from stem cuttings 10-20 inches long from a mature shrub, and set them directly into moist soil, spacing them about 3-6 feet apart to allow for bushy growth. Water regularly during the initial establishment phase, but once rooted, it is drought-tolerant and requires minimal care.

How to Grow

Mexican sunflower care is minimal, which makes them a perfect type for the beginner gardener. Read on to learn how to keep these beautiful yellow flowers blooming all summer. Give them enough space in your garden and their blooms will attract many pollinators including butterflies – like the monarch butterfly – and hummingbirds. 

Light

Mexican sunflowers love full sunlight. They require six to eight hours of sunlight per day and can be very drought-tolerant once established. If you grow Mexican sunflower in partial shade, they will not produce blooms as profusely and will not grow as tall. They may even grow spindly, lanky, and flop over from a lack of sunlight. 

Water

Planting a Mexican sunflower seedling will require more water than an established Mexican sunflower shrub. While they are young, water deeply and often (at least two times per week). Water in the morning at the base and avoid wetting the foliage and blooms as they can suffer from mildew. 

For this same reason, this plant type doesn’t enjoy high humidity, and they need to be properly spaced in the garden to avoid overcrowding and increase airflow. Once the bloom season has come to an end, you can cease watering. It’s also important to note that this shrub does not like wet soil, so when in doubt, it’s better to underwater rather than overwater the sunflower garden. 

Soil

Mexican sunflowers can tolerate poor soil conditions and have been known to thrive in sandy and rocky soil. As mentioned above, the most important consideration for your garden soil when you are growing them is that it is well-draining in order to avoid consistently moist soil. Your soil should be able to dry out between waterings. They also tolerate a variety of soil pH levels and can even tolerate slightly acidic soils. 

Temperature

USDA growing zones 9-11 most closely resemble this flower’s native habitat. They are extremely sensitive to frost and cool weather and should not be grown outdoors until nighttime temperatures heat to 60°F (16°C) and above. 

For this reason, in milder climates with frost looming, start Mexican sunflower seeds indoors in containers (like our Epic 4-cells) about six to eight weeks before your last frost date to ensure that it has enough time to grow and flower in summer.  

In warmer climates without as much frost, sow seeds directly into your garden. Consult the packet of seeds before you sow directly for the length of time from seed to summer bloom. 

Fertilizing

This shrub doesn’t require any fertilizer at all. The addition of some organic matter to the garden planting site at the beginning of the growing season should be sufficient. Once established, they don’t require much watering, or fertilizer. Deadheading the spent blooms will encourage more flowers than any fertilizer will. Chop and drop them into the garden to use as a fertilizer for other species in your garden. 

Maintenance

Deadheading spent blooms is necessary for flower production. Once the flowers have faded, cut them back below the nearest growth point to encourage bushier growth, and more blooms.  Mexican sunflowers may grow too tall to support themselves, and may require staking or training up a trellis. They can spread by seed, which is why deadheading is important.

Propagation

Now that you know how to care for Mexican sunflowers, you may want more of them and wonder how to propagate them. The best and easiest method of propagation is to start them from seed. In USDA zones 9-11, sow seeds directly outdoors or start seeds indoors and transplant seedlings in order to get earlier blooms. 

Since they put out aerial roots, they can also be propagated from stem cuttings. Like tomato plants, Mexican sunflowers can put out roots all along their stem. Remove a section of the stem just below a leaf node. Be sure that the cutting has at least two to three leaves. Place the cutting directly into a pot with soil and keep well watered in a sunny window indoors. Roots will establish within two weeks, and they can then be transplanted outdoors.  

Common Problems

The Mexican sunflower is relatively carefree and low-maintenance. However, there are some signs to look out for when growing that could indicate an underlying issue. 

Growing Problems

Mexican sunflowers require full sun, and most of the growing problems that occur result from lack of sunlight. If you notice that they aren’t blooming in the butterfly garden, that growth seems slow, or that they are spindly and lackluster, then this could be a result of a lack of sun. 

There is no way to remedy a lack of light other than to use caution when choosing a planting site for your sunflowers before sowing seeds. Be sure to choose a spotthat receives six to eight hours of sunlight per day and is not shaded by any other species or structures. 

Since these flowers are known to grow quite tall, they can also be knocked over if grown in a windy or exposed area. It’s not impossible to grow them or start seeds in these types of areas. However, you may need to provide support like a trellis or stakes in order to keep them upright. 

Pests

Since sunflowers are native to Mexico, they are well suited to drought and dry conditions. Most pest issues are a result of wet weather conditions. Slugs and snails can sometimes bother them, especially after extended rainy conditions. If you notice irregular holes in the foliage after prolonged wet weather, then this may be a sign of snails or slugs. 

Place a wet piece of cardboard near where you grow Mexican sunflower to act as a trap. These pests will seek out the cardboard as shelter during the day and can then be easily collected.

Diseases

When you learn how to grow Mexican sunflower, you’ll find overwatering can cause the perfect conditions for fungus to take hold, especially in hot and humid climates. If too much moisture is splashed onto the foliage during watering, then this can contribute to issues with powdery mildew. This mildew appears as a white flour-like powder on the leaves. 

To prevent these issues, always bottom water your shrubs. Spray neem oil as a preventative measure to reduce the colonization of spores on foliage. In advanced cases of this mildew, removing and destroying infected material may be best to prevent it from spreading to nearby healthy plants. After removing infected material (stalks, seeds, and flowers), spray neem oil onto the remainder and nearby plants to reduce the risk of further spread. 

Frequently Asked Questions