On The Gardeners World Website It Recommends Amelanchier As A Tree For Heavy Wet Clay Soils. All Of The Sites Selling Them However

Question

state; to be planted in well drained soil.

Answer 1

It is that it can handle soils that are more on the dense side. It would prefer a more nutrient, and a more loose, soil.

This article will help you with its care:

https://www.gardeningknowhow.com/edible/fruits/serviceberries/growing-serviceberries.htm