There's not much point in planting a parsley root, whether regular parsley or Hamburg parsley. It is biennial which means that in its second year it is genetically programmed to bolt and run to seed. So the only reason to plant it would be to get seed. Or just as an experiment to see what happens. It probably won't grow at all unless you have some of the top of the root where the leaves shoot from.

One good thing about letting second year plants - like parley - flower is that it helps feed all the teeny, tiny beneficial bees and wasps that we really want in our gardens. Also, I think it would be interesting to just see what grows.

If it is planted and bolts, it may produce seeds and self sow. Can always try it and see what happens.

FataMorgana