Mexican sunflower (tithonia) Tithonia rotundifolia
Mexican sunflower (tithonia) (Tithonia rotundifolia) is an annual flowering plant in the Asteraceae family, native to Mexico and Central America. It grows 1.2–2 m (3.9–6.6 ft) tall and 60 cm–1 m (24 in–3.3 ft) wide, wants full sun and low water, and is hardy to about 0 °C (32 °F). Space plants about 70 cm (28 in) apart.
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Mexican sunflower (tithonia) at a glance
| Type | Annual flowering plant |
|---|---|
| Family | Asteraceae |
| Mature height | 1.2–2 m (3.9–6.6 ft) |
| Mature spread | 60 cm–1 m (24 in–3.3 ft) |
| Spacing | 70 cm (28 in) centre to centre |
| Sun | Full sun, at least 8 h of direct sun a day |
| Water | Low; drought tolerance high, waterlogging tolerance none |
| Soil pH | 6–7.5 |
| Cold hardiness | About 0 °C (32 °F) once established (roughly USDA zone 10) |
| Heat stress | Likely above about 38 °C (100 °F) |
| Flowering | about 10–14 weeks after planting, for 9–17 weeks |
| Days to maturity | About 100 days from planting |
| Wind tolerance | Low |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Mexico and Central America |
| Common in gardens of | 🇲🇽 Mexico |
Is Mexican sunflower (tithonia) toxic?
- People: mildly toxic
- Cats: not well documented
- Dogs: not well documented
- Parts: foliage, sap
Sesquiterpene lactones can irritate skin and stomach; not listed in ASPCA toxic plants.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Mexican sunflower (tithonia)
No well-documented helpful pairing. Group it with plants that like full sun and low water.
Questions about Mexican sunflower (tithonia)
- How far apart should I plant Mexican sunflower (tithonia)?
- About 70 cm (28 in) apart, centre to centre. A mature plant spreads 60 cm–1 m (24 in–3.3 ft).
- Does Mexican sunflower (tithonia) need full sun?
- Full sun: at least 8 hours of direct sun a day.
- How much water does Mexican sunflower (tithonia) need?
- Low water. Drought tolerance is high and waterlogging tolerance none.
- How cold-hardy is Mexican sunflower (tithonia)?
- It tolerates about 0 °C (32 °F) once established, roughly USDA zone 10. As an annual it is usually planted out after the last frost.
- When does Mexican sunflower (tithonia) flower?
- About 10–14 weeks after planting, for 9–17 weeks.
- Is Mexican sunflower (tithonia) poisonous to cats and dogs?
- For cats it is not well documented; for dogs not well documented; for people mildly toxic. Sesquiterpene lactones can irritate skin and stomach; not listed in ASPCA toxic plants.
- What grows well with Mexican sunflower (tithonia)?
- There is no well-documented companion pairing for Mexican sunflower (tithonia). Group it with plants that like the same sun (full sun) and water (low).
Sources and evidence
Evidence grade C (C: plausible, mixed evidence).
- RHS Plant Finder, Royal Horticultural Society
- Extension Gardener Plant Toolbox, NC State Extension
Notes and assumptions
- Typical garden-form values; cultivars and local conditions differ.
- Frost-tender, grown as an annual; a magnet for butterflies and bees. Stems can snap in wind.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
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