Mexican sunflower (or red sunflower), T. rotundifolia, is a vigorous, drought tolerant warm season annual that is easy to grow in the ornamental garden. Tithonia plants grow 4-6+ feet tall with a large central stalk and a somewhat gangly branching habit. The stems can be brittle. The dark green leaves are ovate to deltoid (triangular) in shape with serrate to crenate margins. The coarse leaves are usually entire but occasionally will be three lobed. The leaves can also be used to help arthritis, and the petals make a good herbal tea for colds. The foliage and stems are covered with a soft downy fuzz, and the underside of the leaves are hairy.
Because of its tall stature, rangy habit and coarse texture, this annual is best at the back of borders and beds to form a backdrop for shorter plants. It can be used as a seasonal screen (especially if grown from transplants started early in the season). Use in mixed or annual borders with tall zinnias, coreopsis, and other flowers in hot colors for a high-energy planting, or tone down the brilliant orange-red flowers by combining with purple flowers and larger plants with dark-colored foliage, such as annual ornamental millet or castor bean or in mixed beds with woody plants such as smokebush or ‘Diabolo’ eastern ninebark. Tithonia grows best in full sun in poor to average, well-drained soil. Avoid planting in rich soil or heavy fertilization that with promote excess foliage and weak stems. Pinch back plants to encourage bushier growth. Sturdier plants are less likely to fall over but plants often need to be staked to remain upright. Shelter from strong winds if possible. It has few pest problems and is not favored by deer.