Yellow cosmos (C. sulfureus) brings yellow and red flowers into the cosmos clan, but at a cost: Its seeds don't germinate as easily as common cosmos, and its flowers tend to be smaller (2 in. in diameter) than other cosmos. Many gardeners find it easiest to grow from nursery seedlings.
OUR FAVORITES: Bright Lights mix has large (21/2-in.) flowers of yellow, gold, orange, or scarlet on 3- to 4-foot plants. 'Lemon Twist' bears clear lemon yellow flowers on stems to 21/2 feet tall. Ladybird mix grows to only 1 foot in height. Sunny Orange-Red and Sunny Gold top out at 15 inches.