You may have determined in which zone your region is located by referring to the USDA Plant Hardiness Zone Map. [See: The United States National Arboretum USDA Plant Hardiness Zone Map.] For example, I live in Northeast Tennessee, which is in Zone 6. Of course, when you are shopping for plants to add to your landscape, you want to find those plants that are hardy in your particular zone. That, however, is really only the beginning. Different regions, even different areas within the same zone, have their own unique conditions, presenting certain challenges for the home gardener. Nevertheless, recognizing these challenging conditions and then planning for them can save you a lot of time, money, and plants. In this article, I will deal exclusively with more southern regions that are faced with climates that tend to be hotter than those further north.
Hot, humid summers
I should probably begin with my own Zone 6 region and those zones further south (Zones 5-11). In the South, we have very hot, very humid summers. [See my article on Gardening Problems in the South.] This means that a lot of plants that generally like full sun (or so says the tag that accompanies your plant) would actually prefer partial shade in the South, since the sun in the South is much more intense than the sun further north. Also, the high humidity found in the South can result in plants suffering from powdery mildew. This means that Southern gardeners need to space their plants so they will have good air circulation. In addition, we in the South should also look for plant varieties that have been bred to be more resistant to powdery mildew. (There are, for example, certain varieties of garden phlox; e.g., Phlox paniculata ‘Crème de Menthe’ and ‘David,’ that are more mildew resistant than such cultivars as ‘Coral Flame.’) Finally, watering can be an issue in the South, as well. First, Southern gardeners should look for plants that are drought-tolerant. (Daylilies and sedums are always good choices.) In addition, plants should be watered in the mornings in order to allow the leaves to dry before the evening. (This practice can also help to prevent mildew and various other diseases, such as black spot on roses.)
Hot, dry summers
If you live in a region where the summers are hot and dry, as I did at one time in Texas, you should definitely shop for drought-tolerant plants. You also do not want to place your plants close together where they will be competing with one another for water. Once again, there may be plants that need partial shade rather than full sun. (Gardening tip: Do not place a new plant immediately in the ground in the area where you think you may want it to be. Leave it in the pot and place it in the proposed site. It usually takes only a couple of days to determine if the plant will be happy there. I once moved a wigelia all over my yard before a found a place in partial shade where it was happy, despite the fact that the tag said to plant it in full sun. I am happy to report that it is blooming even as I am writing this.) You should also water your plants deeply less frequently rather than watering a little every day or two. This means that you should set your sprinklers and allow them to do their job for at least 20 minutes. This should give your plants at least one inch of water. (To determine if your sprinklers are delivering that much water, set some plastic cups around and then measure the water level after 20 minutes.) An even better solution is to add a drip system, which will also cut down on evaporation. Finally, mulch your plants well to conserve water.
Some areas of the country are prone to droughts. A friend of mine in Atlanta, for example, was calling me often during their drought asking what to do about her plants. If your region tends to experience frequent droughts, follow the same techniques that you would for those regions that have hot, dry summers, as described above. Avoid planting flowering annuals that may look pretty but which require regular, frequent watering. Definitely install a drip system and mulch extremely well so the water can be held in the ground better.
In whatever zone you live, you will always do well by purchasing plants native to your area. Native plants have adapted over the years to the conditions in your region, which means that they are usually more disease resistant and hardier. (If you want a particular plant that might not be as adaptable to your region, then you might consider using it as a container plant.)