Often gardeners believe the optimal time to plant their gardens is in the spring. A fall planting can also be an opportunistic time. We often think that that a spring planting will capture those early spring showers. However, in the past years the spring showers have been very generous and the weather cool which limits access to the garden since the garden is too wet to plant. In some years the spring weather quickly changes from cool to hot. It is the hot dry conditions, beginning too rapidly that can injure newly planted flowers and grasses.
A fall planting from late August through October offers many advantages that often outweighs the spring planting. Transpiration which is the evaporation of moisture from the plant’s leaves stems and flowers is low and root generation potential is high. Usually the fall temperatures are cooler lowering the stress of extreme heat. The fall moisture helps the plants establish a root system. The cooler fall temperatures also encourage root growth since the energy of the plants flows downward as opposed to new top growth. Fall plantings will have a growth head-start with its enhanced roots, making the most of the spring rainfall.
However, if you plant late into the fall season (November-December), the risk of poor root growth can occur and hence an increased failure rate.