Planting at the wrong time. Folks in South Texas plant tomatoes earlier than do those in North Texas. And, likely they plant different varieties of vegetables, each suited to growing conditions. For fall gardens of cool-weather veggies, it's important to know how long it takes the crop to mature and count back2ward from the first expected frost. Your local Extension office is a good source of information on planting times and appropriate varieties, as are gardening publications specific to your area.
Timing also pertins to landscape plants.
Fall is the absolute best time to plant most woody shrubs, trees and groundcovers. They can be planted successfully at other times, but may experience environmental stresses, especially in the summer. Experts vote for the slow-growing, quality tree. Resist the urge to pack it full, remembering that most plants grow quickly. If they're too crowded, they'll compete for food, water and sunlight, creating stress and thus more insect and disease problems.