Fall planting of Northern Catalpa
I usually suggest waiting until the temperatures are out of the 90's during the day for planting. Fall is actually a great time to plant trees, as the soil is still warm which give the roots plenty of time to grow in their new site before winter really sets in.
When planting trees it is recommended to dig the hole no deeper than the root ball and three to five times as wide as the root ball. Be sure to expose the tops of the roots at the crown of the tree so that it can be planted with the crown at grade or just a bit above grade. Never plant a tree below grade.