Yucca plants- how to get rid of them?!?!?!

[lanicastro]

Dh and I bought my grandparents house 4 years ago, and I have been working on bringing the flowerbeds back up to "Grandma's standards" and I need help. She had a yucca that has overtaken a flowerbed and I cannot get rid of it!!! It is in a part sun/part shade bed that I am trying to revamp, and it just doensn't fit into my plans. I have been battling this monster for 3 years. I have dug it out every year but it keeps coming back. I have dug down a foot into the ground and still cannot get to the bottom of the root. Is there anything that I can put on the root to kill it off? It is in a bed right next to a cement walkway and I can't get down any furter to try and dig out the rest of the roots. On a positive note- this one Yucca of grandma's has given me close to 20 new Yuccas which are taking up space in a sunny raised bed that I haven't had time to do much with. They fill it up nicely and don't make it look like I abandoned it! Anyone need any Yuccas????

Thanks, Lynn