An annual is a plant that germinates, grows, sets seed and dies within one growing season. Whether a plant is cold hardy or not is not connected to being an annual, perennial or biennial.
Cypress vine is a native annual tropical vine of the Americas, but has naturalized in Florida and the Gulf Coast areas; said to be cold hardy to Zone 6. Fine lacy or thread-like leaves twine as it grows, putting on scarlet red flowers in summer. In addition to being a climber, it can be used as a groundcover.
Tansy aster is an annual native to the Southwest and throughout the Plains even into Canada. Fernlike, or tansy-like (tannacetifolia) light green foliage with beautiful aster-like lavender flowers with yellow disks about 1 1/2 to 2 inches across. Blooms from late spring through fall. A once a month watering will keep the blooms coming throughout the summer. It will keep its compact shape in lean, poor soil but will become much larger in well amended soil. Minimal amending is recommended. Tansy aster is another example of our natives plants giving so much, asking so little in return.
The old fashioned larkspur is a drought tolerant reseeding annual, previously associated with delphiniums (now in the Ranunculaceae family). I’ve grown it in my alley, in the xeristrip, and its crept into my medium water-use zone. Deadheading keeps millions of tiny seeds from overcoming your garden next year, and also keeps the blooms coming. Larkspur can flower for six weeks. Again, deadheading is important to prevent a massive infestation throughout your landscape.
Our showiest native wildflower; an annual. Little care required. Grows along roadsides and in natural areas throughout our region. Gaillardias are popular these days, with many new introductions all the time. G. pulchella is a good choice for seeding in prairie areas with other native grasses and wildflowers.
Sweet pea is another wonderful old fashioned, fragrant annual climber. That is, the original L. odoratus was fragrant; many varieties today have had the fragrance bred out of them to achieve more and bigger blooms and different colors. Sweet pea is versatile and will grow in a variety of water zones and soil types. I have seen it growing alone for 2 years at an abandoned home, alongside lantana. Some gardeners just toss out the seeds in fall or spring and wait to be surprised.
Native wildflower that likes it lean and mean. Over watering and well amended soil will usually cause Blackfoot daisy to die a premature death, even for a short lived perennial, such as it is. It would be an ideal border plant, similar to alyssum, if not for its tendency to move about where it will (that is, die where you plant it and seed somewhere else). Still, it’s worth a try. Our Panhandle xeric gardens should never be without Blackfoot Daisy. In fact, once you plant Blackfoot daisy and let it seed, you should never be without it (and that’s a good thing).
Most notable in the meadows and fields of California, the California poppy grows throughout the southwest. Considered to be both annual and perennial, it either comes back the next year or it reseeds. Once you have a stand established, it should continue in your landscape, but not invasively so. This past summer of 2012, my California poppies bloomed in both the spring and our unusual fall. Blooms in April and May. Finely cut blue-green foliage make an attract plant outside the bloom period. The foliage should die back in summer.
Desert marigolds are one of the prettiest desert flowers. The plant forms a neat compact rosette of finely cut silvery green leaves from which stems emerge topped with a bright golden daisy like flower. It is considered either an annual or short lived perennial. Scatter seeds from the spent plant to insure its return the next season. Over watering will doom this beautiful plant. Desert marigold can be seen blooming in the desert in winter and spring. In my garden, it's blooms begin in May and will continue sporadically into fall. Not awfully reliable in cold hardiness here.
One of North America's favorite annuals. There is much variety in size and colors of flowers, ranging from yellow, golden, orange, red/orange, red and mahogany. The plants themselves can vary from 3-4 feet to 8 feet or more. Seeds sown in springtime will be insure blooms in late summer or fall. Great for cut flowers.
Native to the plains, Coreopsis tinctoria, has naturalized throughout most of the U.S., especially in disturbed soil. Prefers moist sandy soil. An annual, it may last more than one year. Very showy flower with yellow outer rays, with a maroon blotch towards the center ray. Sow seeds in early spring. Heat tolerant, once a month watering is recommended for well drained soil.
Snow on the Mountain is a showy plant native to the plains states. Heat and drought tolerant in the Texas Panhandle. Striking variegated green and white foliage, with small white summer flowers. Can be invasive and is toxic to humans, sap of plant may cause dermatitis. Deer resistant. Control spread by deadheading.