Q.Planting a memorial willow tree
What is the best time to pant a willow tree in southwest Virginia and what type would be best for a baby’s memorial garden?

Fall or early spring are good times to plant new trees.
These articles have more information for you on the care of Willow Trees and other possible trees for your memorial.
https://www.gardeningknowhow.com/ornamental/trees/willow/dappled-japanese-willow.htm
https://www.gardeningknowhow.com/ornamental/trees/willow/grow-a-willow-tree.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/watering-newly-planted-tree.htm
http://pubs.ext.vt.edu/450/450-237/450-237.html