Cosmos bipinnatus
The hardest thing about growing warm-season flowers is deciding which ones to actually have in your garden. Wander through rows of started plants at the nursery or peruse seed racks and you'll see the dilemma. There's everything from A for ageratum to Z for zinnia - and many dozens of annuals in between.

So, how to choose? First, figure out how much time you're willing to devote to the project. You could plant a dozen marigolds along the driveway and call it a flower garden. Or, you could study colors, growing heights and care details for a never-ending floral tapestry throughout summer and fall. Another option is simply to choose seeds and plants that catch your fancy and hope for the best. Regardless of which path you take, here are a few flowers to consider:

Cosmos are the easiest of the "easies." They are sun-loving, multi-branching and come in heights that range from knee-high to 5 feet or more. These daisy-like charmers vary from bright and bold tones to the softest pastels. Cosmos can be started from seed in spring or from transplants anytime in spring and summer.

Another carefree choice are sunflowers, which most people think of as being brilliant yellow. However, thanks to breeders, sunflowers now come in an assortment of yellow-bronze-red hues, all of which are highly valued as cut flowers. Whether the choice is the Russian Mammoth, with its single huge head on a towering stalk, or one of the numerous multi-branching varieties, it all starts with seeds either sown directly in the ground or started in small pots and then transferred to chosen spots. Let some flowers go to seed to self-sow for the next season.

The name nasturtium doesn't sound very romantic, but don't be fooled. This old-fashioned, ultra-easy flower from South America brings quick color to the garden through the hottest part of summer.
Sunflowers
(Jack Hollingsworth/Valueline/Thinkstock)
Either from seed or transplant, trailing nasturtium crawls over the ground to fill wasted spaces or climbs daintily on a low fence or wall. The small blossoms are also edible, with a peppery taste that will dress up a salad. Another bonus: Nasturtium reseeds itself.

Zinnia, another effortless candidate, has brightly colored petals and does double-duty in cut-flower bouquets. There is nothing boring about zinnias, which produce heavily through fall: Choose big-flowering varieties on tall plants for accents, or tiny ones called Peter Pan that work in low borders and in containers. The trick to growing zinnias over a long period is to keep water off the leaves, as moisture causes them to develop mildew. Otherwise, just make a home in your garden for them and get ready for months of gorgeous blooms.