Forest garden design

I have a sort of basic (or so I thought) question about forest garden design.  basically spacing.  And I realize that there are a million variables and nature does not worry about spacing and symetrics etc.

just for arguments sake though say we have a guild based off a nut tree that will have a 50ft spread when mature then I have some elderberries with a 12 ft spread and then maybe some bush cherries  again all just for argument.    so standard practice would have the apples spaced at about 30 ft  and I know you space the large trees farther to allow for sun penetration    but where does the mulberry go?  8 ft out to compensate for itslelf?   

I cant find any info on this in gaias garden or several other books I have?

Thanks

I'm no professional but this is how I work thinigs out in my property.

I generally go from the canopy layer trees that are tallest, I figure where the bottom branches will be ..and density..I'll generally put shorter trees or dwarf fruit trees under the canopy but on the south, or possibly east or west side, where they can get some sun and water...same with shorter bush layer, under the canopy of the shorter trees but where they can get some sun..

you can put sun lover herbaceous layer in the south, and possibly east and west of the guild, and put your shade lovers in the herbaceous layer in the north or heavier shade ares of the guild..also put in your spring bulbs such as your barrier daffodills just about anywhere, as they will not bloom when there are leaves on the trees if you are in a northern zone...not sure in south about the bulbs...if you aren't losing leaves.

if your trees are sturdy you can put vines up through them, but if not you can place vines up an arobr or trellis or post whrever there is a gap that needs filling.

that was sort of my basic concept as far as planting under the tall trees.....just allowing the understory the space it needs.  I was just imaging all this unnecessary shade being created in any other way.  Thanks for the reassurance.

It definitely depends on your climate too.  In our hot summers here, most things like a bit of shade.  I've tried to make most of my overstory trees relatively open canopies though, so they only cast a light to moderate shade (e.g. pecan, jujube, japanese raisin).  Here, this means almost anything could still be grown underneath, but in cooler climates that would not be the case.

Have a look at plants in your area and how they grow.  I don't think it can be said enough that observation is massively valuable in knowing your local environment.

Forest gardens so far appear to err on the side of too much density.  I think this is mentioned of Robert Hart's garden in the case study in the book Edible Forest Gardens.