Answer: You may not be getting all the roots when you transplant, or the site isn't very conducive to growing. Start by amending the planting bed with organic matter to make the soil loose for the new little roots. Then prior the move, simply water them well the day before, then dig them up with a generous rootball (enough soil to take all the roots plus some extra) and replant immediately. Water in and you're done. You might also consider waiting until next spring to transplant them, when they are a bit larger and able to take the move a little better.
Good luck with your coneflowers!
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