One of the tallest of all annual plants, often known as the Mexican sunflower, Tithonia rotundifolia can grow 1 to 2 m tall. It hails from Mexico and Central America. It has stunning large, orange flowers rather like a Dahlia - the colour of the petals really glows. The blooms appear in mid-summer through to autumn, above coarse, heart-shaped foliage. The plants need a sunny location, with well-drained, good soil. Water when the weather is dry, but don't overwater them. They bloom best in a hot summer. I am hoping they will self-sow in my garden in future years (as they are reputed to do) as I have never had any luck growing them from seed. My success with the Mexican sunflower came when I was able to purchase sturdy seedlings at a plant stall. However, if trying from seed, sow these direct into the ground in spring once the soil has warmed up. Be vigilant for slugs and snails, which enjoy eating the young seedlings. Because of the ultimate height of the plants, cradle stakes are useful to support them. Deadhead spent blooms to prolong the flowering period, but leave a few for self-seeding if required! Give the plants an occasional feed of soluble fertiliser. There is a dwarf form, called 'Goldfinger', but I prefer the tall version.
I pair my Mexican sunflowers with tropical-looking companions such as Canna, Dahlia, Odontonema tubaeforme and red Salvia 'Josh', to provide height and colour from mid-summer onwards in my hot-coloured border. Purple or blue flowers would also look fantastic with the fiery orange daisy flowers. Dark leaves, such as those of Persicaria 'Red Dragon', Pennisetum setaceum 'Rubrum' and coleus cultivars provide a welcome contrast. I also like Mexican sunflowers with lime-coloured leaves: such as the luscious foliage of Salvia elegans 'Golden Delicious', Duranta erecta 'Sheena's Gold' and lime-leaved zonal Pelargonium. Mexican sunflowers last well in a vase: seal the hollow stem in boiling water before placing them in water. The flowers attract bees and other nectar-seeking insects.
POstscript: I only enjoyed these annuals for one summer. They did not self-seed and I never saw seedlings for sale again. Further attempts to grow them myself from seed sadly failed!