It requires the same conditions as a shrubby hydrangea - organic, moisture retentive soil that is on the acidic side. Hydrangea trees are typically paniculatas which are quite sun tolerant so at least half day sun is suggested.

Tree-form hydrangeas are simply shrubs that have been trained to a single stalk. They are rarely grafted. The stalk/trunk does not really elongate much so the height it is now is about as tall as it will get. The topgrowth can and often does extend quite a bit so you may need to prune to keep this in check and to encourage the development of strong stems that will support the heavy blossoms.

Here is a link that might be useful: Info on Hydrangea paniculata