Temperatures are cooler and there is an increase in rainfall. Roots can establish until the ground freezes which is typically Mid-December in Michigan.
Use a fertilizer with mycorrhizae to promote root growth.
Make sure root flare is level with the ground. Mulch the area around the tree flare leaving a donut hole around the trunk.
Fall watering is important
Newly planted trees and shrubs need more consistent watering than established plants. Established plants need approximately 1” of water per week and newly planted trees and shrubs need up to 2” of water per week. When watering, deep soak the root ball.
Overwatering can happen, so check the soil before watering. The soil should be moist about an inch down, if dry then water. Evergreens are susceptible to winter burn. Fall watering gives them a reserve of water to get them through the winter. Water them until the ground freezes.