If I understand your question, correctly, the answer is yes, you can use the stump grindings as one (or more, depending on the volume) of the layers in the lasagna garden. It would be a high carbon layer.

Start the shrubs in a new location if possible. The hole where the trees came from will have nutrient depleted soil and the remaining woody material will require some time to decompose, locking up available nitrogen in the process.

So go ahead put the shrubs in this fall. If you do use fertilizer, make sure it's low in the first number ---> 0-10-10, if such a thing exists. The soil dug out of the hole should be fine.

Covering the grass with wood chips will not have improved the soil by next spring. How can covering grass with wood chips improve the soil underneath? If your aim is to kill the grass, then the mulch will have to be left on over the summer growing season since the grass is dormant during the winter.

Thanks, bpgreen and cowgirl2!

bpgreen, yes, I want to use the grindings as one of the layers for the "lasagna" - thank you!

cowgirl2, do you mean it's OK to put the shrubs in the holes, as long as I use good planting soil, even if the surrounding soil is pretty depleted from nutrients because the trees were there before? Also, I do not plan on just using the stump grindings over the grass for the lasagna bed, I plan to have layers of compost etc. too.

Thanks again!

No, dig a NEW hole for your shrubs. You can fill in the old holes with that soil and put compost in with the shrubs if you have it.

If you are going to garden, you got to do some digging.

Thanks, cowgirl2! Yes, I have been digging quite a bit... I just wonder about the holes where the trees were because they were at the perfect location where the shrubs would look very good. That's why I was wondering...

It all depends on the type of garden, digging is optional with some types of gardens. It all depends on the type of garden, types of plants, and importantly on the local conditions.
Stump grindings are good for lasagna layers, make sure you have some high Nitrogen sources to balance the carbon.

Thanks, tclynx! I plan on using a lot of compost (I don't have the facility for doing my own composting so I will order it from a company) for my layering, so I hope that will provide a lot of nitrogen for the bed. Do you have any other suggestion please?

Thank you again!

Grass clippings provide lots of nitrogen. Another method to add some nitrogen might be to get some grain meal from a feed store. This like alfalfa meal, soy meal, or other grain meals will provide a potent source of nitrogen. Some people use these things like pelleted fertilizer around their gardens and yards.

Finally, if you are short of cash, an easy way to balance a carbon source like sawdust is to sprinkle urine over it.

Compost is the finished product of mixing carbon/nitrogen sources. It will likely not provide enough nitrogen to balance the sawdust. However some finished compost to help fill out your beds will be helpful. Any other organic materials you can find to layer in will be good.
Grass clippings (high nitrogen)
leaves (good carbon)
hay (nitrogen)
straw (carbon)
coffee grounds (nitrogen)
Sawdust (carbon)
Urine (nitrogen)-make sure to cover to avoid odors
paper (carbon)
feed pellets (nitrogen)
rice hulls (carbon)
kitchen scraps (nitrogen)
cardboard (carbon)
etc

tclynx, thank you so much for the very helpful list! I really appreciate it! I have got some very great ideas now. Thank you again!

If some high Carbon material, the woody material from those stumps, is mixed into the soil the soil bacteria will get busy digesting that woody material and will consume all the available Nitrogen in your soil to make the protein they need to do that. After they work away and die off that Nitrogen will be returned to the soil, but that can be 30 days or so.
However, if that material is spread on the surface and it is not mixed into the soil the bacteria will not get right to work on it and will not utilize all available N in your soil and there will be no N depeletion. The soil bacteria will digest that woody material, used as mulch, slowly over time and you will not see plants deprived of N.
So it depends on how that materail is used what happens.

I think you can go ahead and plant the newer plants right in the holes that you want to use. You just have to know that two things are likely to happen, and to compensate for those events.

Here's a quick sketch:

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Now if that hole is filled, with the stump grindings, you have far more than what is optimal for "percentage of organic material", or "percentage of organic matter". You could be up to about fifty percent organic material (the wood, more or less ground up), but I won't quibble if you insist that the number is drifting toward 25%. It's probably somewhere in between.

The optimal percentage for a landscape soil is around five percent, perhaps a tad less.

So what will happen? It will subside, as the wood rots. (I'm sorry, I meant to say "naturally decomposes"). If you're prepared for the subsidence, meaning that you're going to add topsoil on the top, there isn't really much problem. If you're going to be amazed, ("Gee, why is the dirt sinking?) then yes, there is a problem. But that mix of wood chips and topsoil can be pretty rich, and I like to use it, often, and I do. But I add dirt, frequently, in smallish amounts, as the subsidence takes place. I plan for it, inspect it, and add as needed. But you have to guess, in advance, how much of that wood is going to rot (essentially all of it) in the next five years, and figure 'how much of that filler in that hole is going to go away? Thirty percent? Twenty? Ten?' And, of course, you're going to have to add topsoil. Just add topsoil, NOT topsoil with peat: that would be just repeating the situation, wouldn't it? Peat, like all organic matter, 'naturally decomposes', and it goes away. And these lawn guys who add 'enriched' topsoil (with peat) rather than just plain old non-peat topsoil, can't figure out why their lawn is not level, five years later.

The other aspect is the 'nitrogen gets used up'. It doesn't really. As Kimssr pointed out, that nitrogen may be 'busy' for awhile, or unavailable to the plant, but if you plan on adding a 'gentle' nitrogen source, such as Milorganite, every now and then, sufficent nitrogen will be available to the plant, and the plant will thrive.

It may be just a matter of personal choice, or how much you're available to supervise the growing of this plant, once you get it in the hole. If you're generally not available, you may want to get rid of the rich woody mix, and put just native topsoil into the hole. If you're available, and like the idea of supervising, from time to time, what's happening there in the hole, it can be alot of fun, and that plant is going to thrive.

kimmsr and philes21 - I cannot thank you enough for your very helpful information! See, I knew that I would get the best information from the other members of GardenWeb :-)

I think I know what to do now. I need to remove some of the stump grindings from the holes right now, mix in a lot of top soil and organic matter, and then just plant the shrubs in there. It is a bit more work but I think it will be worth it. It's a shame that I can't get Milorganite in my area, but I am sure there will be other alternatives. Maybe I can get some alfalfa pellets.

Thank you so much for making this so clear and helpful to me. I truly appreciate your generosity in sharing your knowledge and time to help out this newbie here! Thank you again!

*The stumps were ground up to this very fine mixture of wood and soil*

Stump grindings make excellent mulch. It will greatly improve the soil where you put it. Mulch is usually spread in a two-inch-thick layer around plants to preserve moisture in the ground and prevent weeds from taking hold.