Bob wrote:
about half of the dandelions are breaking off about 6 to 8 inches down.

Una wrote:
Not to worry. Dandelions won't regrow from the tap root; just get
the crown.

brooklyn1 wrote:
That's not true. If any part of the taproot remains it can regrow new
dandelion plants.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7469.html

The source here explains that a piece of taproot as short as 1 inch
can regrow. However, in my experience the conditions have to be
very favorable, meaning the piece is near the surface (in the crown
zone), soil moisture is good, etc.

Also, although the common dandelion (Taraxacum officinale) is a
perennial plant, survivorship over winter fairly poor. So again,
eliminating seed set is the first line defense against this weed.
When I have less time or the ground is dry and hard, I sometimes
merely pinch off the flowers.

Because plants in flower can set seed after being grubbed out, and
because the roots can regrow, dandelion remains should not be left
behind as mulch. I put all dandelion remains on the compost pile,
covered.

Una