Answer: Lagerstroemia indica x fauriei 'Natchez' grows to about twenty feet tall and wide. I would suggest a minimum of at least ten feet back from the wall to allow space for the roots. Another reason not to bring it too close to the edge is that the soil will be extra dry along the wall. To some extent too it depends on how your wall is constructed. You might want to consult with your landscape architect who designed the wall.
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