Smothering tree roots?

We’ve got 9 mature sugar maples growing along the north side of our driveway. Id like to plant berries (raspberries, blackberries, gooseberries and thimbleberries) and, since they cast so much shade to the north and the driveway is to the south, i was planning on sheet mulching around them and planting little berry guilds around their bases. I’d leave at least a foot of space around the tree trunks though. And prune branches up 15’ or so for more light and airflow.

I have pine sawdust, pine slabs, maple leaves, horse manure, compost and pine woodchips to work with. My main worry is that by sheet mulching around the trees that I’ll suffocate their roots. Is that likely?

What if I only sheet mulch like 6” deep or so?

Or what if I lay the pine slabs first, bark side down, so that they act as a weed barrier and also wont lay totally flat with the ground. Leaving an air gap for a few years until they decompose?

Any opinions?

Why do you need to sheet mulch at all?  

I'd be leery of putting that much material on more than 20% of their root area.  It would be a shame to lose that amount of syrup production.

Personally, I would dig potholes, amend the soil, and plant the understory shrubs in them with simple mulch on top. They will be competing with the trees for water, so it will take some hand-holding to get them established.

Brody Ekberg wrote:

I have pine sawdust, pine slabs, maple leaves, horse manure, compost and pine woodchips to work with. My main worry is that by sheet mulching around the trees that I’ll suffocate their roots. Is that likely?

What if I only sheet mulch like 6” deep or so?

I'm curious to hear an expert opinion on this. I often find myself in similar situations and worry about adding soil when I'm near to a tree. I'm semi-convinced that I nearly killed a juvenile apple tree by building a 1' raised bed too close to it. My earthworks projects have been ongoing for 7 years, so I'm constantly put in this situation.

Mike Haasl wrote:Why do you need to sheet mulch at all?  

I'd be leery of putting that much material on more than 20% of their root area.  It would be a shame to lose that amount of syrup production.

We arent set up to make syrup anyway. We usually collect sap from a tree or two just to drink, but dont have an evaporator or a lot of free time to make syrup. And I want to sheet mulch because I have an abundance of materials and dont want them sitting around rotting when they could be growing food for us.

if you go to a big old city, like New York city, there are mature very healthy  trees lining streets and concrete and asphalt cover all the roots except maybe a 3 or 4 foot square where the tree trunk rises.

I've piled up to 2 feet of soil right up to the trunk with no ill effects. If anything, the trees actually grow better!