Mulberry in a tree

I imagine that a bird ate a mulberry, landed on this big (non mulberry) tree, and pooped into the scar from a large branch being cut. A couple years later, we have this mulberry growing in the tree. Sort of cool, sort of horrible.

Mulberry tree

Mulberry. Fast growing tree with fruit that is edible but is, by general consensus, not particularly delicious. The fruit looks like small blackberry, and birds eat it and poop the seeds all over everything. Sidewalks under mulberry trees are stained red-black, as the fruit is prolific. 

It has the ability to get a foothold in man-made surfaces, so is often growing in cracks in sidewalks and pavement, through which physical removal is nearly impossible. Often you will see smaller plants on very large root bases where they were cut back year after year, but continued to grow.

Look for it everywhere, but particularly in neglected areas, along fences and in alleys.