How to Grow Mexican Sunflowers

Mexican sunflower

The Spruce / Evgeniya Vlasova

At winter's end, gardeners rush to the seed aisle of the garden center, looking for something fast growing that will transform the landscape in a few month's time, much like the annual Mexican sunflower that quickly leaps to shoulder-height and beyond when temperatures heat up.

Mexican sunflowers yield dozens of showy daisy-like blooms with petals in fiery colors of red, orange, or yellow, all with yellow centers. Plant seeds or seedlings in the spring to enjoy an ongoing display of profuse blooms throughout the summer into fall.

Botanical Name Tithonia rotundifolia
Common Name Mexican Sunflower, tree marigold
Plant Type Annual
Mature Size 3 to 8 feet
Sun Exposure Full sun
Soil Type Average to poor
Soil pH Acidic; 5.8-6.5
Bloom Time Summer and fall
Flower Color Yellow and dark orange
Hardiness Zones 9 to 11 (USDA)
Native Area Mexico and Central America

Mexican Sunflower Care

Mexican sunflowers are ideal for the beginner gardener who wants pops of color to fill in a large blank spot in the flower border. They're also great for cut flower arrangements while producing enough to attract scores of butterflies and beneficial insects like parasitic wasps. These flowers aren’t fussy about soil and don’t need much care after they start growing. 

These annuals are a welcome addition to the butterfly garden thanks to their nectar-rich shallow blossoms that meet a pollinator’s needs. Unlike many butterfly-friendly plants that are small in stature, the tall blooms of the Mexican sunflower bring butterflies right up to eye level, making them easier to observe. A mature stand of the sunflowers makes a good addition to the vegetable garden, as the pollinators they attract will help increase your vegetable yields. 

One packet of Mexican sunflowers will give you many vasefuls of cut flowers throughout the summer. Plant them with companions that thrive in the same sunny site and average soil, like cosmos and zinnias, which will also act as cut-and-come-again blooms for the cutting garden. 

Mexican sunflower plant with tall thin stems and orange flowers on top in garden

The Spruce / Evgeniya Vlasova

Orange Mexican sunflower

The Spruce / Evgeniya Vlasova

Mexican sunflower plant with large green leaves and orange flower on top of thin stem

The Spruce / Evgeniya Vlasova

Light

Full sun is a critical factor in growing healthy Mexican sunflowers. Plants growing in shady areas may not bloom, will flop over, and might suffer from fungal diseases. 

Soil

Save your soil amendments for fussier flowers like roses and dahlias, because Mexican sunflowers like lean soils with a low nutrient content. Good drainage is important, to prevent problems like root rot. Sandy or rocky soils more closely resemble the native soils of Mexico where the plants grow wild. 

Water

Mexican sunflowers are drought tolerant throughout their life cycle, contributing to their low maintenance charm. Wet soil is not tolerated by Mexican sunflowers, but if your area gets more rain than average, you can compensate for this by planting in soil with excellent drainage. 

Temperature and Humidity

Mexican sunflowers love hot weather, even days with triple-digit temperatures. Conversely, cool weather stops the Mexican sunflower in its tracks. When nighttime temperatures are in the 60s, it’s the right time to grow Mexican sunflowers. Average humidity is best for healthy plants. Provide extra spacing for plants in humid areas to prevent powdery mildew.

Fertilizer

Mexican sunflowers grow just fine without any supplemental fertilizer. In areas with especially depleted soils, you can add an all-purpose flower fertilizer at the beginning of the season to get plants off to a quick start.

Mexican Sunflower Varieties

‘Torch’ is the mainstay of Mexican sunflowers, growing in gardens since the 1950’s. ‘Fiesta del Sol’ and ‘Goldfinger’ are dwarf varieties for smaller gardens or containers, growing in height between 2 and 3 feet. 

Mexican Sunflowers vs. Sunflowers

Mexican sunflowers and common sunflowers (Helianthus annuus) are both tall, sun-loving annual flowers that tolerate dry and poor soils. Common sunflowers usually have larger blooms, sometimes in excess of 12 inches in diameter, and many varieties also have edible seeds. Grow the two complimentary sunflower plants at the back of the border for a visual and pollinator feast.

Common Sunflowers
Common Sunflowers

Sasa Pokimica/Getty Images 

Pruning

Pruning Mexican sunflowers isn’t necessary, but can help to get lanky plants under control or to keep overgrown plants in bounds. Keep in mind that you may sacrifice some blooms when pruning. Cut off the top one-third of the plant when it’s experiencing a lull in blooming to both deadhead and tidy the plant.

Propagating Mexican Sunflowers

Although the Mexican sunflower is easy to grow from seed, if you can’t find your favorite variety you can also propagate plants by stem cuttings. Here's how:

  1. Take two or three stem pieces.
  2. Cut them down to about 12-inches tall.
  3. Remove all but one pair of leaves on the stem.
  4. Cut the remaining leaves in half, as they are too large to be supported by the cutting.
  5. Add root medium.
  6. Insert about 6 inches of the stem into moist, but loose potting soil.
  7. Keep in a filtered sun location; water daily.
  8. Expect roots to form in about 10 days. 
  9. Transplant outdoors in about eight weeks.

How to Grow Mexican Sunflowers From Seed

The small, triangular seeds of Mexican sunflower germinate easily in warm, moist soil. The quickest approach is to sow the seeds outdoors, at the same time you plant tomatoes, two weeks after the last frost. In short summer areas, zone 4 and colder, start the seeds indoors six weeks before the last frost to ensure the plants have time to mature and bloom before fall. 

Because of its large size and rapid growth, plant no more than a few Mexican sunflower seeds in a container. Sow seeds directly in the pot, as large plants are difficult to transplant. Use a soilless potting mix with good drainage. 

Potting and Repotting Mexican Sunflowers

Gardeners with small plots can grow dwarf varieties of Mexican sunflowers on the patio, deck, or balcony. Plant the Mexican sunflower in the center of the pot, and add trailing plants like million bells or portulaca, which also appreciate full sun and dry conditions. 

Common Pests

Snails and slugs sometimes bother Mexican sunflowers, especially in rainy weather. Place a piece of damp cardboard beside plants, and collect the pests when they hide during daylight hours.