New Growth In My Lilac Tree-- What Is IT?????

I have a series of large lilacs in my New England yard. I cut back the leader branch of one them 3-4 years ago as it was growing straight out and collapsing. Apparently, last summer, the new leader branch (the thickest, strongest root branch) changed its foliage completely. I just saw this yesterday as I had been away, but it is back this year. Apparently, it grows very fast, so is already much taller than the rest of the same tree, has totally different leaves, no lilac buds and some fuzzy, almost caterpillar looking green spiny puffs all over the branches from that one root branch, and there are new shoots from the bottom that look similar. The other 3 main branches look like normal lilacs. I am certain this branch used to be a normal lilac as well.

What is it??? What would cause it to change like this? I believe the lilacs are all 20+ years old. Any ideas???

Thanks! Kristen

 

sounds a bit like a willow has seeded amongst the lilac shoots.

 

I suppose it could be a type of willow, but there are no other willows nearby, and would it take root on ONE branch and not the rest of the tree? Why would one branch succumb to the willow seed?

 

Could this be a chimera - a mutation?

 

Could very well be - a photograph would be interesting.

 

I will get a photo and post it on Friday. Thanks so much for helping me figure out this bizarre mystery!