Gives trees time to establish before onset of hot dry summer.
Soil conditions often better in the Autumn than Spring.
Less drying winds assists establishment.
Greater variety of tree stocks available in Autumn.
Often more time in Autumn for farmers to devote to preparation, planting, weed control, post planting care, etc. than in Winter/Spring when feeding out and lambing/calving, takes most of the available time.
Any losses can be replaced in Spring thus avoiding the loss of a year's growth.
Note:- Autumn planting is not recommended in areas which experience severe winter frost or snow. Spring is best in these situations.