Black Walnut - Will it close a canopy?

[Treeflea24]

I have a section of property that is full of black walnut. It is nearly monolithic in terms of tree species. This is a naturally formed stand, and Id estimate the average spacing to be ~12'-15' between trees, but very variable. I'd estimate the average DBH to be 6-8" for these trees, and avg. height of 30'. 
The ground below these trees is full of grasses, raspberry & other thorny stuff, poison ivy, honeysuckle, flowers, etc. There are trails through here that will get overgrown if not mown regularly.

My question: Will the walnut eventually form a closed canopy and shade things out to get to an open dirt/leaf litter forest floor? Is this species slower than others to form a canopy? 



 

[Texas Ranger]

Short answer, yes.  However, at some point you will need to thin the stand, walnuts like space.  You will have a lot of sun light on the edges, by the picture anyway, some some mowing will still be required.