Annual
Mexican Sunflower
Tithonia rotundifolia · Asteraceae
Also called: Tithonia, Red Sunflower, Clavel de Muerto
Mexican Sunflower (Tithonia rotundifolia) is a low-water annual well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate.
Mexican Sunflower at a glance
- Water use
- Low (established)
- Sun
- Full sun (needs 6+ hours; tolerates intense Tucson afternoon sun once established)
- Mature size
- 4-6 ft tall and 2-3 ft wide in one season (dwarf cultivars 'Fiesta del Sol' stay 2-3 ft)
- Growth rate
- Fast
- Bloom
- Brilliant orange to scarlet-red daisy flowers with yellow centers, Summer through fall (June frost-free start; peaks in monsoon heat July-October)
- Cold hardiness
- Frost-sensitive; killed by first hard freeze. Grown as a summer annual in USDA 9a-9b Tucson.
- Soil
- Tolerates poor, rocky, or sandy native desert soil; needs good drainage. Performs in alkaline Tucson soils without amendment.
- Native range
- Mexico and Central America
- Best used as
- Pollinator and butterfly garden, Back-of-border accent, Cut flowers, Quick summer screen or filler, Xeriscape color
- Wildlife
- Magnet for butterflies (especially monarchs and queens), bees, and hummingbirds; goldfinches eat the seeds. Excellent pollinator plant for low-desert gardens.
- Toxicity
- Generally considered non-toxic / low concern for pets and children; not on the ASPCA toxic list. As with any plant, ingestion of large amounts may cause mild GI upset, so discourage chewing.
How to grow Mexican Sunflower in Tucson & the low desert
Watering
Warm-season annual: direct-sow or transplant after last frost (March-April) for bloom through the monsoon and into fall. Water deeply 2-3x/week to establish, then weekly; quite drought- and heat-tolerant once rooted. Avoid overwatering, which causes floppy, leggy growth.
Fertilizer & nutrients
Light feeder; thrives in lean soil. Too much nitrogen produces foliage at the expense of flowers. A single application of balanced or low-nitrogen slow-release fertilizer at planting is plenty in Tucson's warm soils.
Pruning & care
Pinch young plants once to encourage branching; deadhead spent blooms to extend flowering. No structural pruning needed; pull at first hard frost.
Notes
One of the best heat-loving summer annuals for Tucson; thrives in July-August when many flowers fade. Provides bold height; may need staking or pinching in wind. Reseeds readily. Plant in spring for monsoon-season color.
Sources: University of Arizona Cooperative Extension; Pima County Master Gardeners; Arizona-Sonora Desert Museum