What adaptations of dandelions ..?

Question

what adaptations of dandelions make them

such difficult plants to get rid of ?

Answer 1

And a sort of rapid evolution on a bi-individual scale (it is the incorrect use of the term, but hey...).

Variation in leaf & stem lengths, etc, that positively contribute to you allowing them to live are quickly passed on to the next generation.  Taraxicum officinale is a plant that partakes in parthenogenesis... which essentially means that if it isn't pollinated, it will produce seeds anyway by cloning istelf.  Thus, individual colonies of dandelions could (technically, and dependent on whether you are a "splitter") be classified as at the very least a sub species.  You may have noticed that plants in oft' mowed areas are very prostrate, while plants at the backs of flowerbeds can be quite tall.

Answer 2

They have a very long taproot, which if you don't remove all of it when "digging" dandelions out of your lawn allows them to grow back.

The seeds are tiny and are attached to the "parachutes" which allow them to travel a considerable distance carried by the wind.  So even if you manage to get rid of them, they'll repopulate from others in the area.

And dandelions produce a large number of seeds per head, so one dandelion turns into hundreds.