When is the best time of year to do a landscape installation?
It is true that Fall and Spring are generally good times to plant. Plants that have been dug from nurseries in the fall are generally dormant and less likely to stress from transplanting. The dormant season allows the plant's root structure to grow and become established before energy is expended in the Spring and Summer to produce top growth. Regularly scheduled watering in the winter months is still necessary to help plants survive.
Some definition of "Fall" is needed as it relates to the landscape industry. The digging season associated with "Fall" has more to do with the dropping of leaves and moisture content of the ground than a specific date on the calendar. Rainy periods in the fall make digging and transport of plants from the fields difficult...conversely, dry periods in the fall make digging difficult because it becomes more difficult to keep soil undisturbed around root balls.
When planting in the summer months, additional care and attention will be required to insure plant viability. Plants that are to be installed in the summer should be dug from the nurseries early, "healed in" to protect roots from drying out, and carefully monitored from the time of installation throughout the warmer months.
