[InterCounty]

Constructed a new patio and planter wall at my home last summer, with the intention of making a privacy hedge behind the wall with emerald green arborvitaes.

Between the fence and the wall is about 5' and the run is 40' long.
The wall is 12" high and the ground was dug out another 6" lower then the base at it's deepest.

I plan on spiking 6x6's close to the fence so I can fill in the void so that it is level with the bottom of the wall cap.

Would filling in the entire 15 yards or so with top soil would be overkill? Or should I use some clean fill on the bottom?

Guess I'm wondering what the best course of action is here.
Thanks

 

[MTEC]

Of course clean fill 5 inches of soil is good

 

[InterCounty]

So your saying only 5" of top soil is needed?

What if I plant six footers and the root ball is 12"-18"?

 

[MTEC]

The roots need soil to the drip line of the tree. So roughley 16 in ball 20 in of root soil is good. Clean fill is 25% of the cost of a good potting soil. And just top dress 4 ".