Staghorn fern. Cool plant. Here is a link that might be useful: photo of a staghorn fern

Hard to see from the small picture but it could be Hedera helix, Ivy. Bay and ivy both have black berries so maybe that's where the confusion came from.

It's Araucaria heterophylla, the Norfolk Island Pine. Many discount stores sell them as "indoor Christmas trees" in December -- that's the clue you left that made me think of the NIP.

Not a doubt in my mind with the supporting photographic evidence that it is knotweed. I would have come to the exact same conclusion just based on your description - the rapid spring growth; the hollow, bamboo-like stems and even the coloring are all classic attributes of this pernicious weed.