help w/ acacia sprouts

Hello all;
I have an acacia tree ~ 16 yrs old, about 12" diameter at the knee and ~35 feet high. Its located along the fence-line w/ my neighbor and had grown over their house so early this spring I pruned it back heavily, and took off some large branches. All together I took off about 1/3 of the crown.
About a month afterwards I had the lawn tilled to replant grass. Before I could lay the sod, LOTS of little acacia trees started sprouting up from roots everywhere under the former dripline. I mean a LOT, but only in my yard, not my neighbor's.
I tried spraying them w/ Round-up, thinking they had sprouted from seed. Some died, some didn't. Today, I just finished pulling them all out by driving a shovel through the roots (1/2 in - 1 in thick) above and below the shoots. It was a major PITA to do.
I'm reluctant to lay sod until I've got the acacia shoots under control. Any suggestions as to how to do that? If I use Round-up will it kill the main tree? Is there a proper way to deal w/ this?
Thanks a heap, -jbb
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This may be the solution. Crowd them out?
Acacia has the potential to protect poor soils from erosion and revive their mineral content. Acacia can grow on poor soils including clay, limestone and unstable sand dunes, even soil tainted with uranium wastes. It is also able to survive fire, dry spells and seasonally waterlogged soil. (In fact, the seeds germinate better when placed in hot ashes!). The tree also contains nitrogen fixing bacteria which can help rejuvenate these poor soils. The tree prevents soil erosion because of their extensive and dense roots and heavy leaf litter. But the seedlings don't grow well in the shade and in competition with weeds, so for deliberate planting, the seedlings have to raised elsewhere first.
"J.B. Bobbitt" wrote:

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Celestial Habitats by J. Kolenovsky
2003 Honorable Mention Award, Keep Houston Beautiful
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