Q.Root system
What type of root system does the chaste tree have? Are you able to grow in a large container and keep it pruned back to a small tree or oversuzed shrub?
A chaste tree growing in a pot will appreciate a moist but well-drained soil. Constantly soggy or wet soil can and often will cause root rot or other harmful or deadly plant diseases. Therefore, I recommend using a quality potting soil or potting mix, or a 50/50 combination thereof in a container with a drainage hole(s). You can also add about 10% pumice or perlite to the soil mixture to help with drainage.
Make sure to choose a container with drainage holes at the bottom and one that is large enough to allow for 2 to 3 years of growth before having to shift up to a larger size container. This might mean your planting pot would be 8 inches or more in width than the root ball of your chase tree.
Note: Keep in mind the wind. When planting taller growing trees in containers, wind is always a factor. Choose a pot with a low profile and make sure to place your container where it will not be exposed to high winds. Square pots tend to be more stable than round pots. You can also place a brick(s) or other heavy objects in the bottom of the container for stabilization.
