The field behind my yard was full of this last year and i had
seedlings popping up all over the place. I was out there pulling some
of them today and there are a lot of plants with roots a centimeter
thick at the top and the few that i managed to pull out were 6 inches
long.

According to the information i've found online, these weeds grow for a
year and seed in their second year after which they die. But what
about their ability to regrow from their taproot if they never get a
chance to seed?

I'm wondering if i can just go and cut each of them off right at grass
level with a garden knife and not bother trying to pull up the root.
That would be very easy and go really really quick compared to trying
to pull up each one by the root. Will this effectivly kill them or
will they continue regrowing year after year from their taproot until
they get a chance to seed... and then die?

I'll continue to get the dandilions roots completely. Damn those are
annoying.

Any thoughts appreciated.