French marigold

Tagetes patula is an annual, occasionally reaching 0.5 m (1+1⁄2 ft) tall by 0.3 m (1 ft) wide. In some climates it flowers from July to October. In its native habitat of the highlands of central Mexico, blooms are produced from September to killing frost. Achenes ripen and are shed within two weeks of the start of bloom. The heads contain mostly hermaphrodite (having both male and female organs) florets and are pollinated primarily by beetles in the wild, as well as by tachinid flies and other insects. The leaves of all species of marigold include oil glands. The oils are pungent. It can grow in both sandy and clay soils provided they have good drainage. It requires full sun to partial shade.

The dried and ground flower petals constitute a popular spice in the Republic of Georgia in the Caucasus, where they are known as imeruli shaphrani (= 'Imeretian Saffron') from their pungency and golden colour and particular popularity in the Western province of Imereti. The spice imparts a unique, rather earthy flavour to Georgian cuisine, in which it is considered especially compatible with the flavours of cinnamon and cloves. It is also an essential ingredient in the spice mixture khmeli suneli (reputedly as significant to Georgian cuisine as garam masala is to that of North India).

This plant is valued for its velvet-textured, brightly coloured blooms in shades of yellow, orange and russet in summer. It is shorter, and has a more spreading habit, than its relative the Mexican marigold (Tagetes erecta). It is therefore more suitable as an edging plant in the open border. Moreau et al 2006 attempted to protect Solanum tuberosum (potato) against Leptinotarsa decemlineata (potato beetle) by intercropping with T. patula but instead found it acting as an attractant, resulting in greater infestation and lower yields. (They also found the same for another purported repellent, Armoracia rusticana.) Tagetes patula is frost intolerant, given a Royal Horticultural Society hardiness rating of H2, capable of surviving temperatures of 1–5 °C (34–41 °F) but killed by freezing temperatures. They are grown by gardeners in moderately fertile, but well-drained soil in full sun with evenly moist conditions.

Cultivars. Hundreds of cultivars have been developed, of which the following have gained the Royal Horticultural Society's Award of Garden Merit:-