Glad I found this thread. Just got the game a couple days ago. I thought dandelions not respawning was a bug. Turns out it's because I put a marker and weed plank pallet next to every patch of dandelions I find.
Instead of, or in addition to the radius, maybe allow markers and pallets to be placed next to dandelions without inhibiting their growth? I find it useful to place a pallet near 2+ dandelions so I can cut them all down and put the planks that I can't carry in the pallet so they are easy to find later.
Come to think of it for markers it might be a good rule in general to ignore them from inhibiting growth of anything.