I would. You should never put anything in the planting hole, except lime, when planting new trees.

The grass clumps won't burn any roots so no worries there. But any fresh or undecomposed organic matter will shrink and reduce in volume substantially as it breaks down and starts to decompose. So the planting hole and possibly the tree itself could settle and sink as the grass clumps start to break down.

ETA: the grass clumps are no different than the soil dug for the hole.....they are just soil with some existing vegetation attached :-)) NBD!! And I'd have to question the lime comment above. It is rarely necessary unless you soil pH is excessively acidic (below 5.0) and when necessary, it is applied to the entire planting area, not the planting hole. What comes out of the planting hole goes back in........NOTHING else!! (since the grass clumps were removed as part of preparing the planting hole process, they can safely be reincorporated (given the caveats previously stated).

No you do not need to dig out the buried grass clumps. They will not burn the tree roots as they decompose. You just might need to do a little weeding around the trees if any of the grass survives being covered in cardboard, wood chips and buried.

What you should do is fertilize the new trees when they break dormancy to add some extra nitrogen to the soil that gets used in the decomposition process.

Awesome, thanks guys! I started reading about anaerobic issues and panicked because I remembered laying the sod directly on top of some of the bare roots as I buried the hole back up with dirt.

What a huge relief because replanting would have been a major pain! But I was willing to do what it would take to secure my investments.

You don't say what type of trees these are, but I will say that it is hard to go too wrong planting bare root fruit trees. All you really have to do is dig a hole, and plant it at about the depth it was originally grown at. Bonus points for getting it perfectly straight once the soil is packed in. I have fairly casually planted over 35 bare root fruit trees in the last few years and have only had a two of them fail.