AGERATUM. While not fastidious in the matter of soil, the ageratum prefers a dry but gritty soil to a stiff, damp medium. If put out in May the plants flower from June till October. The dwarf garden forms of the species Mexicanum may be used as bedding plants. Such sorts as Imperial Dwarf Blue, Countess of Stair, Swanley Blue, and Heavenly Blue, with slate blue flowers from May to September, are commonly grown as annuals. Pron. Aj-er-ray’-tum.