The Mexican sunflower (Tithonia diversifolia) is an annual flower that has many names. It’s also known as the Bolivian sunflower, tree marigold, golden flower of the Incas, Japanese sunflower, and just Tithonia.
As you may have guessed by its name, this plant is native to Mexico and Central America. Its daisy-like blooms resemble traditional sunflowers, only they’re not members of the Helianthus genus. That said, they do come in shades of orange, red, and yellow like standard sunflowers, with contrasting blue and green foliage.
These plants are popular pollinators, known to attract the following:
- Butterflies, especially Painted Ladies and Monarchs
- Eastern Tiger Swallowtails
- Spicebush Swallowtails
- Giant Swallowtails
- Pipevine Swallowtails
- Eight-Spotted Forester Moths
When grown in a vegetable garden, you can use Mexican sunflowers to attract pollinators and other beneficial insects to help your crops thrive.
Mexican Sunflower Varieties
Mexican sunflowers tend to grow between 36 and 72 inches tall on average. As a result, it’s easy to view helpful pollinators like butterflies that are attracted to the flower’s nectar. Although Tithonia and Helianthus are different genera, they’re both in the Asteraceae (daisy) family along with asters, echinacea, dandelions, and other favorites.
Like all plants, Tithonia come in different varieties, including:
- Fiesta del Sol: This dwarf variety is perfect if you have a smaller planting area to work with, as its bright yellow, red, and orange blooms will only reach around 36 inches tall.
- Tithonia diversifolia: One of the most common Mexican sunflower varieties, it boasts large, showy yellow blooms. These plants can often grow 3 to 4 feet tall, although they can sometimes reach 6 feet.
- Tithonia rotundifolia, aka “Torch”: Expect this variety to grow to anywhere between 3 and 8 feet tall. This option is easy to grow in garden beds, and the plant offers stunning red or bright orange dahlia-like blooms. Monarch butterflies are especially attracted to this variety, and you can expect to see swarms of them during their migrating season.
- Tithonia rotundifolia, aka “Golden Flower of the Aztecs”: Also called the Red Torch Mexican Sunflower, this variety offers stunning red-orange flowers that are around 2 or 3 inches in diameter. Butterflies are attracted to this plant all season long.
- Tithonia speciosa, aka “Goldfinger”: A smaller variety, Goldfinger will reach around 2-3 feet in height, making it great for planting in containers. This species is known as the Goldflower of the Incas, and you may see Tithonia rotundifolia Goldfinger varieties as well.
How to Plant Mexican Sunflowers
Plant your Mexican sunflowers from seed for the best results. This process is very easy—even for beginners—because the seeds are quite large.
If you live in a colder region (below USDA zone 6), however, you may have better results by buying a seedling to replant in your garden, or sowing seeds into a starting container about a month before the final frost date. Some varieties, such as the T. diversifolia, can even be started by using stem cuttings from another plant. T. rotundifolia does well when planted in containers or as a privacy screen in your yard.
No matter what variety you select, they’ll bloom from summer until the first frost strikes. Plant these flowers all around your garden’s periphery for a colorful border, or use them to bring extra attention to a water feature.
Best Time to Plant
Plant Mexican sunflower seeds in early springtime. You can start the seeds inside around one or two months before the season’s final frost, or sow the seeds directly into the soil outside after the frost risk is over. Sow the seeds into moist soil, well-draining soil, gently pressing the seeds about half an inch into the earth.
If you live in the northern region, plant them indoors and move them outside after the final frost has passed. You can plant smaller varieties in containers and set them on your porch. They’ll do better in warmer climates when planted outdoors after the soil reaches 60 degrees.
As mentioned, sowing seeds indoors can help if you live in a colder area. Start the plants in trays around 8 weeks before the final frost of the season, and press the seeds gently into the soil’s surface Keep your home around 70-degrees, and the germination time will take around a week or two.
These plants will thrive in USDS hardiness zones 3-11. However, certain varieties will do better in various locations. Tithonia diversifolia, for example, is hardy in zone 9 while the “Torch” varieties do well in zones 10 and 11.
Place these plants in a full-sun location. Annuals do best in a full-sun spot, as they can tolerate heat and lower water conditions. When planting, select a location where the color will look nice during the late summer after your perennials begin to fade.
Well-draining soil works best for these plants. While the soil should be moist when you plant the seeds and remain moist until the seeds sprout, maintaining dry to average moisture levels is ideal. Mexican sunflowers do well in poor soil or dry conditions, but they won’t tolerate damp soil that’s overly rich in organic matter.
Space Between Seedlings
Leave plenty of room for the plants to grow. Because Mexican sunflowers can grow quite large, you’ll need to space the seeds at least two feet apart.
You can expect any type of Mexican sunflower seed to germinate around 4 to 10 days after planting. The Torch varieties require heat in order to germinate, and it’s important not to bury any type of Mexican sunflower seed too deeply or the seeds won’t germinate. Sprinkle the seeds with a scant 1/4-inch of soil at most.
How to Care for Mexican Sunflowers
Caring for Mexican sunflowers is simple, as these plants practically thrive on neglect. In fact, they require little to no care on your part other than regular waterings.
Mexican sunflowers have average water needs: just be careful not to overwater them. Allow the top few inches of soil to dry out completely in between watering. One way to know when they need a drink is that the foliage will begin to appear wilted when they require water.
If your Mexican sunflowers are tall, you may want to stake them to prevent them from toppling over. It’s not unheard of for some varieties to reach 8-feet-tall in the right growing conditions. Part-sun locations may require staking more than full-sun spots as well.
Don’t worry about fertilizing your plants too often. Most varieties don’t need fertilizing at all, but you can use an all-purpose fertilizer early in the planting season to encourage growth, or if you notice your plants need an extra boost.
Although this plant is very easy to care for, you will need to deadhead the blooms every two to three days during the late summer. The flowers grow vigorously during this time, erupting in a pop of bright color.
If the plants begin to spread into an unwanted region (which is more likely to happen if you live in a tropical climate), you’ll also need to prune them back. Although, Mexican sunflowers aren’t considered invasive plants. Tithonia varieties could spread on their own when your plants drop seeds.
Birds will eat your plants’ seeds, and heavy winds may knock them loose as well, but the heads will still get heavy when they’re in full seed. Cut the plants back every so often to release some pressure from their bases, which will encourage them to grow bushier.
Common Problems when Growing a Mexican Sunflower
Luckily, these plants don’t suffer much from serious pest or disease issues. They’re hardy, deer resistant, and the T. rotundifolia variety attracts beneficial insects such as the minute pirate bug to your garden. Slugs and snails may also be attracted to this popular variety, but the damage isn’t typically serious.
Companion Plants for Mexican Sunflowers
Plant your Mexican sunflowers with the following plants:
- Canna – These tropical plants are bold and colorful. Plant them outside with Mexican sunflowers if you live above Zone 9, or indoors if you live in a location with cold winters. Make sure to purchase these plants from a source your trust, however, if you want to avoid the mottling virus.
- Castor beans : Grow these fast-growing beans and Mexican sunflowers together, since they grow at the same rate and are great to cultivate with your kids. Just be aware that the seeds are toxic.
- Nasturtiums: Another perfect companion for a veggie patch! Both of these options will grow easily from seed and work well in poor soil conditions. You can choose from climbing or spreading varieties, and plant them next to your Mexican sunflowers to fill in the gaps.
A Final Thought
Growing various types of Mexican sunflower plants really is incredibly easy. The blooms are bright and cheerful, and make a great addition to any summer garden. You’ll love watching the butterflies that these plants attract! To bring a spash of vibrant color into your home, try using these blooms in your own cut flower bouquets in late summer when you have to deadhead the plants anyway.