How deep to dig to remove grass?

Hello all. I'm planning a small garden bed and planting a few fruit trees/bushes as well as some flowering trees. Grass will need to be removed from all these areas and I'm wondering how deep I will need to dig to reliably get the grass out? I see info online suggesting that grass roots can go 6 inches or deeper? Not sure what type of grass I have but I'm in Green Bay WI and the grass should be native as the home is 70 years old. I can rent a sod cutter but that'll only go 2.5" deep. Thanks!

you'd be better off covering it with cardboard and soil and leaving it to compost.

So just dig my hole for the plants and plant them accordingly and add cardboard under my mulch? What about above the root ball? Seems like the top edge of the root ball would be directly exposed to the grass and the grass would be able to grow under the cardboard and over the roots, no? I'm going to be inoculating the roots/soil with mycorrhizae and growing wine cap mushrooms in the mulch. Would the cardboard method affect this plan at all?

check out "sheet mulching" or "sheet mulching cardboard" on youtube

depending on how much soil you put on top you might not need to punch any holes. The cardboard will decompose by the time the roots get there and the roots will punch through whatever is left.

even if a little grass makes it through its easy to hand weed.

I did beds two ways, some I put some much compost on top of the grass I didnt even need cardboard, the others I started the first year as straw bale beds and the second year added compost to them and the third year completely covered them with compost and they are just raised beds now.

You can also use lots of newspaper and the roots will grow through easier.

I have a couple hundred square feet of gardens that were all grass originally. I only dug one small area the first year before I learned it wasn't required.

All those grass roots are good for the soil, especially as they are decomposing. As far as mycorrhizae leaving existing root structures for them to take the path of is better not worse.

In my experience if you just try to kill off grass round a tree or shrub with cardboard, some of the grass will always find its way through the gap by the stems, and then it's REALLY difficult to pull out!  In answer to the original question, the shorter the grass generally the shallower the roots.  I would cut out the square of turf where I'm going to plant, say a foot or so square.  You will see which are the roots of the grass and which are the rhizomes which is where the regrowth actually happens, beause the latter are thicker and have little sprouty bits. Dig the planting hole a little deeper than you need and put the turf back in the bottom UPSIDE DOWN.  Then plant and mulch as you like over the wider area between the trees/shrubs.  

I think if you're removing sod, 2-3 inches should be enough to get the rhizomes.  If you're leaving grass roots in the ground, that's fine.  

Sheet mulching with cardboard is a good option too.  Just dig your planting hole, put in the tree, cover the surroundings and much of the root ball with cardboard (overlap so that the slots in the flaps don't let the grass come up) and cover it with mulch.  If you're on a slope, try to overlap it so that the cardboard is shingled the opposite way you'd do a roof. So water running down a piece will go under the next piece and infiltrate.  Mulch it heavily away from the tree and less near the trunk (<1").  If you want to plant seeds around the tree, pull back a spot of mulch and put an equivalent amount of soil in that spot.  Stab a hole in the cardboard with an old knife (unless the cardboard has started to break down already) and plant your seeds in the soil.

I'm enjoying Charles Dowding's videos of no-dig gardening.  https://www.youtube.com/channel/UCB1J6siDdmhwah7q0O2WJBg

I agree with the others that sheet mulching is a good way to start by smothering the grass, but you probably will want to identify the type of grass before starting.
I learned from experience that cardboard with more than 6 inches of wood chips on top isn't enough to stop Bermuda grass. It just waited over 6 months for the cardboard to break down, and it pushed right through the layer of wood chips. Then, when I pull it, it breaks the stem at the original ground level, so I get some roots, but it still has enough to wait until my back is turned to shoot up another sprig (and runners right under the surface of the mulch in an effort to take over more space.

A few weeks ago I was planting some kale in an empty space in the forest garden where the chips were still quite thick. I dug down in the chips to get to the soil surface and found the bermuda, alive and well, growing under the 6-7" of mulch that has been on top of it since last August. Honestly, I now wish I would have dug out the top 4-5 inches of soil before mulching to remove as much of it as I could. Sure, I saved time last year by just piling the mulch on top, but now I have to spend 30+ minutes every few days to go over that part of the garden and pull up the rogue sprouts that made it to the surface to stay ahead of it so it doesn't get any more established. If I don't miss anything during the routine inspections, I suspect it will give up someday; but for now I suspect that time I saved just mulching has been more than made up with the time spent combing through the area to find the little sprouts that are preparing to reclaim the space. (sigh).

Wow, thanks so much for all the advice everyone. I'm in Wisconsin so not Bermuda grass. I lived in Florida for 20 and do not miss it at all.  So when placing 6" of hardwood mulch, that does mean 6" above grade correct? Do you remove some topsoil so that the top of the mulch isn't so far above grade?

6" is 6".  I wouldn't dig out any soil I didn't have to.  Just pile the 6" onto whatever you have and you're all set.  Or do 7" if no one's watching...

(Go Pack Go)

what most of us are saying is dont remove ANYTHING

anything you remove will be your best topsoil and best organic material.

There are tons of no till and no dig videos on youtube as well as tons on sheet mulching.

Its not rocket science.

I didnt use mulch I put finished compost on top of my grass, just piled it right on top, no preparation at all. Each year I add more compost.

most people suggest newspaper or cardboard sheet mulching to have a better guarantee of not having much grass or weeds. If I did it again I would have done that. But my beds re now 6 years old and this is the first year we've had to do significant weeding and thats only because we let them go last gardening season.