Medium Sized Annual Flowers

Yellow Annuals

• Cool climates agree with the pot marigold, an annual that yields bright yellow flowers during May and June. In some instances, this 1- to 2-foot-high flower continues blooming into the fall months. The foliage of the clasping coneflower, a species growing to 2 feet, appears to grab onto and clasp the stems. The yellow rays of this flower circle a brown center. Yellow varieties of salpiglossis are available, as are melampodium; both species grow no taller than 3 feet.

Blue Annuals

• The cornflower, featuring blue-purple flowers, is a member of the aster family, growing to 3 feet. Place them in full sun, since the stems start to lose their rigidness and begin to droop down in shady areas, according to the Missouri Botanical Garden. Bindweed, China aster and Swan River daisy are other medium-sized annuals with blue flowers. The blue-eyed Mary overwinters as a minute plant under the snow during winter, developing from seeds that take hold in the fall. It grows to 2 feet high, and it often grows in bunches, making it a candidate for woodland gardens.

Pink Annuals

• Slender false foxglove blooms late in the growing season -- from August into October. The flowers are pink and remain open for a single day on the wiry stems. This annual does best in somewhat damp areas. The maximum height to expect from lemon beebalm is 30 inches. Pink varieties exist; this is an annual landscapers use to attract hummingbirds, butterflies and bees. The tree mallow is a medium-sized annual appropriate for containers, with the pinkish blooms making a good choice as a cut flower.

White Annuals

• Plant the prickly poppy in soil dominated by gravel since this white-flowering annual tolerates such conditions. The prickly poppy features an extensive taproot, making transplanting this species relatively difficult. White flowers on a China aster often reach widths of 5 inches. This annual blooms throughout summer and it grows to 3 feet high. Other annuals with white flowers include specific cultivars of species such as cilantro and snow-on-the-mountain. Magilla is a cultivar of perilla with small white flowers that actually survives the winters in U.S. Department of Agriculture plant hardiness zones 10 and 11, but is an annual anywhere colder than that.