I've posted several times before on this problem.

I had a black acacia tree ~16 in diameter. I pruned it heavily ~7
yrs ago and it sent up HUNDREDS of root suckers every year. About
1-1/2 years ago I took it down completely, leaving a stump ~10 inches
above grade.

More suckers. LOTS of suckers. It's ruined my lawn and garden.
Round-up weakens the foliage but won't kill them. I finally used
Ortho "Poison ivy & Tough Brush Killer" late last year. It seemed to
kill them but we'll see if they come back.

'k, here's the Q: I got a powder stump killer. Directions say to
drill 1" holes all over. I got a 1" bit and it won't go in even an
inch (wood too hard, even after 1-1/2 yrs). So I tried a 1/2 in bit.
After 3 holes to 10 inches it broke off.

Any ideas how to killthis stump and stop the suckers?

Thanks a heap,
-Zz
"Zz Yzx" rhymes with "physics"; or " Isaacs" if you prefer.
http://www.abandonedbutnotforgotten.com/zzyzx_road.htm