The problem with planting a fast growing tree is that it would shade the slower growing live oak, causing them to not grow well at all or at best to lean and grow crooked looking for light. I suggest you keep the trees a distance apart to prevent this. Two faster growing trees include Chinese elm and Shumard red oak. With fertilizing and watering during dry spells even a live oak can be greatly speeded up! Apply a cup or two of turfgrass fertilizer per inch of trunk diameter each year in early March, early May and late June.
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