What can I do to grounded soil to ensure proper drainage for my citrus trees?
Certified GKH Gardening Expert
Amendments are the key to improving drainage. It sounds like you have an established tree, so reworking the soil will not be an option. You will want to consider using the lasagna method to amend the soil then. This article will help with that:
You won't need to build a raised bed, but you can lay the amendments on the soil and they will work in over time.