are you sure that root actually belongs to the fir
tree???
is it possible there was some other bush in that spot that has been cut down - and the stump and/or part of the root system was left?
when i bought my house, the previous owners had cut down a bush in the back yard...the second summer i was here, a shoot started
growing out of the stump. i let it grown and now i've got the bush back.
could be the same thing here.
the leaves look very familiar and so does the growth and branching pattern. looks just like what's in my neighbors yard - i have no idea what it's called though.
i DO know that it spreads pretty well...i have to cut back whatever grows through my fence two or three times during the summer. seems to me (not that i've looked too closely because the fence is in the way) that it will root if part of the branches touch the soil...