I need to move an oak tree that has rooted through the bottom of the pot and stands about 8-10 feet tall. It is way too close to the house and must be moved. I know this should be attempted in its dormant state but that is not an option right now. Luckily, this is the Pacific NW, so the weather isn't very warm yet but the tree is leafing prolifically already. I will only be able to dig just a bit larger than the diameter of the pot which is approximately 2 ft. I know we need to handle the tap root with extreme care, and transplant into larger pot, fertilize, water well for months. Anything else?
Part of the way we "handle with care," is to add a mycorrhizal inoculant to the soil when replanting the tree. This helps ensure that the tree develops mutualistic relationships with beneficial fungi and maximizes the ability of the newly limited root system to draw nutrients from the soil.
Occasionally, especially if the soil into which we are planting is compacted or otherwise less than optimal, we'll do some radial trenching around the root ball and fill the trenches with compost to give roots an easy path along which to spread.