"Pushed out of her heavy clay soil" ?? Could you explain that?

Every time she has had an echinacea, it has been doing fine for a couple of years, and then ended up with the top part of the roots on top of the soil and soon after dying. I should clarify, that heavy clay is nearly pure and clay. The fields and her has yellow clay patches, where nothing will grow, because the clay is that pure. Dandelions grows fine I her garden though, tap roots and clay soil or not.

The tap root will hit the bottom and start circling. Eventually this will push the rootball up off the bottom. You'll probably need to do root pruning.

You can also try using fabric pots (smart pot/root pot/root pouch/root pro/etc), they claim they will prevent this from happening by having the root reach the side, hit an air gap, and stop growing.