September is the ideal month for gathering soil samples to be tested by the Extension Service that serves your area. The quality of the sample is very important, so avoid collecting when the soil is very wet or when fertilizer or other additives have been recently applied. Obtain boxes and forms from the Extension Service and follow directions carefully for best results.
To ensure you'll get the spring-flowering bulbs you want for next year's garden, order now while the selection is good. Don't plant yet, though. Wait until the soil temperature drops into the 50-degree Fahrenheit range, or they may start to sprout. In the mean time, store them in a cool, dry place or in the vegetable bin of your refrigerator. Wherever you put them, keep them away from apples, because apples give off ethylene gas which can rot bulbs.
Evaluate the Landscape
As the summer season begins to wind down, take stock of the garden. Note the plants that didn't live up to expectations and those that exceeded them. Make a note of insect and disease problems, too. Most importantly, look for areas that need renewal. Fall is the best time to rebuild cool-season lawns, remake perennial beds, and plant woody ornamentals and spring-blooming bulbs.
Clean Beds and Borders
Good sanitation in beds and borders is always important, but a little extra diligence now can prevent problems later. Pull weeds before they go to seed, remove dead leaves as they fall, and grub out thugs that have spread beyond their bounds. Then, spruce up with a light layer of fresh mulch to restore the garden's tidy appearance.
Transplant Trees and Shrubs
Fall is the best time for transplanting woody ornamentals, because as heat, disease, and pest problems are decreasing, rainfall is increasing. Wait until deciduous plants start to show fall color and you will know the plants are entering their period of dormancy. Roots will grow, however, as long as the soil temperature is at least 42 degrees F (nearly year round in the Middle South). Remember to dig the hole slightly less deep than the root ball, but at least twice as wide. Water, even in winter, when rainfall is lacking, but don't fertilize for at least a year.