It sounds like you have removed all of the top growth and you just have the large tap root remaining. The plant is going to continue to send up shoots from the tap root to establish leaves. This is the plant’s survival mechanism to regrow shoots to photosynthesize and make more sugar to strengthen the root. If you do not want to dig out the root, your objective is to keep any growth from the tap root cut off. The root will try to establish more growth and if you remove it, the root will continually shrink and get weaker. As long as no growth stays on long enough to photosynthesize, the root will continue to decline.

A second option is once growth starts from the root, treat it with a herbicide – triclopyr or glyphosate. This will transfer the systemic herbicide to the root. If you continue to treat any new growth, you will continually weaken and ultimately destroy the tap root.

Alternately, you could apply the herbicide directly to the cut surface of the tap root. This will be absorbed by the root and start the decline process.

Always be careful and apply the herbicide according to the label instructions.