Avoid rotting stumps and logs. I planted in a 6 foot tall rotting stump that became a pile of dirt in less than a year. That made the clue useless.

That means that rotting stumps are useless for landmarks too. Northern Utah (where I box) is dry enough that these things stick around for years, while other places (apparently) will go away quickly.

Lots of good things to keep in mind! Thanks all!