Tithonia diversifolia aka Mexican Sunflower

Tithonia diversifolia also goes by the name Mexican sunflower. It belongs to Asteraceae, the daisy family. Its native range spans Mexico and Central America. It grows in the tropics, in places with a dry season. In Guatemala, it grows in damp thickets. It also grows on dry slopes with scrub. People grow it for its flowers and other uses. They also gather wild plants for medicine and fuel.

It may live for one year or a few years. These forms are annuals and short-lived perennials. Some plants grow woody stems and look like shrubs. Annual plants may have one stem or just a few branches. A listed garden height is about 10 feet [3 metres]. The wider reported range is 3–16 feet [1–5 metres]. The range reflects its varied forms, not one fixed size. In the right climate, it can bloom all year. It can also set seed year-round. Insects move pollen between its flowers.

This plant suits gardens in the tropics and subtropics. In cooler places, growers can use it as a summer annual. It needs sun and soil that drains well. It suits soils with a moderate level of nutrients. It can grow in a range of soil types. It grows best at daytime temperatures of 15–31°C. Its reported tolerance spans 12°C to 38°C. It prefers annual rainfall of 1,000–2,000 millimetres. It can withstand some drought despite this preference. Growers can sow seeds straight where they will grow.

Gardeners grow Mexican sunflower for looks and as a companion plant. Reports link its use near crops to better soil. They also link this use to higher crop yields. Its stems provide fuel, too. In studies, leaf oil has helped keep mosquitoes away. Substances in the leaves can kill insects. Tests have also used leaf extracts against fungi that cause plant disease. Its spread beyond gardens is a key concern. It has become a weed in many tropical and subtropical areas.

Useful Tropical Plants lists no known food uses for this species. It also lists no known hazards. This does not mean the plant is safe. Traditional medicine uses it to ease pain and inflammation, or swelling. Studies found that leaf extracts act against pain, swelling, and bacteria. These findings relate to extracts, not proven garden remedies. They do not show that the plant is safe to eat.