If you wanted one annual to grow in a sunny garden, I would suggest the beautiful, daisy-like cosmos. It is one of the easiest flowers to grow from seed sown directly on the garden bed (after all danger of frost has passed). Its flowers come in a variety of bright colors and styles. You can plant 12-inch-high dwarf cosmos, or 4-feet-tall giants, and anything in between. The light flowers on wiry stems and feathery foliage add movement to the garden. Best of all, cosmos is top rated for attracting birds, bees, beetles, moths, and butterflies. It blooms from late spring to the first frost of fall. Pollinators love cosmos.
Cosmos need sun and heat, and they relish poor soil. Do not fertilize it at planting. Soil that is too rich will weaken their stems and diminish flowering. To keep the flowers growing, trim a third of the way down after the first bloom. The taller varieties of cosmos require protection from the wind. Lastly, give it air and room—they do best when not crowded.
A popular cosmos variety is ‘Dwarf Early Sensation Mix’ (Cosmos bipinnatus ‘Dwarf Early Sensation Mix’). This prolific cosmos gives you an early start and grows to only 12 inches tall. Its large single flowers come in a variety of pinks and whites. Plant this rugged flower in the garden, meadow, or in planters. Lovely for early summer bouquets.
Sulphur Cosmos (Cosmos sulphureus) is a cosmos species that typically grows to 1 to 3 feet tall. It is native to Mexico, loves high temperatures, is drought tolerant, and is bushier than the classic wildflower cosmos. It has semi-double to double flowers that range from yellow to scarlet red. The popular ‘Diablo’ sulphur cosmos is a reddish orange and grows 24 to 36 inches tall. Dwarf Lemon sulphur cosmos grows just 18 to 30 inches tall and features lemon-yellow flowers. It looks great interplanted with perennials.
The pure white, daisy-like blooms of ‘Sonata White’ cosmos (Cosmos bipinnatus ‘Sonata White’) draw butterflies by the dozen. The flowers are held atop wiry stems above feathery foliage on relatively low-growing plants. The long-lasting, compact white flowers are perfect for garden beds or containers. It’s great in vases, too. The 24-inch-tall plants thrive in poor dry soils and can be mixed with other sun-loving annuals such as zinnias and tall verbena (Verbena bonariensis).
Cosmos Picotee is one of the most beautiful of all the beloved cosmos. Its white or pink flowers are edged with distinctive bright rose-red, and it has a vivid yellow center. Self-cleaning and easy to grow, these plants reach 3 to 5 feet tall and bloom from early summer until frost. It makes a striking backdrop in a flower bed. They are tough and do well in hot weather and poor soil. For a shorter but similar bicolor look, try the early-flowering ‘Cosimo Purple Red-White’ cosmos cultivar, which produces 18- to 24-inch-tall bushy plants.