Answer: And you thought Grandma planted marigolds (Tagetes) because they were easy. Maybe. Or maybe she found the spirit of a crowded dancehall in their feisty, festive colors. These diminutive dancers will bloom their heads off for months, in tangy shades of red, orange, and yellow. The Bonanza series of French marigolds have double flowerheads. T. ‘Bonanza Bolero’ (pictured) was a 1999 All-America Selections winner. It grows 10 to 12 inches tall.