Literally translated, Tannenbaum is "fir tree", not "Christmas tree", which would be "Weihnachtenbaum". In German, Christmas is Weihnachten, which is literally "consecrated night". Christmas Eve is Weihnachtenabend. Regardless of the language lesson, there are still plenty who sing Tannenbaum without a thought to literal translations. The same applies to the fish who see this fly. They could care less about Teutonic semantics.
This fly is similar to a Zug Bug, though there are distinct differences.
Hook: Mustad 79580 / 4XL wet fly
Body: Gold mylar tinsel
Ribbing: Red mylar tinsel
Tail: Dyed red hackle fibers
Body: Green peacock herl, one long strand, shaved on one side
Thread: Black monocord
This is a fairly straightforward fly to tie, no hidden tricks, except for stripping and gluing the base of the herl. Before starting, take an Exacto knife and carefully shave one side of the herl so that it can be cemented and sit flush against the tinsel to prevent sliding and breaking of the herl.
Lay a foundation, cement lightly. Tie in the tail, tinsels and herl. Apply a second light coat of cement to the foundation and wrap the gold forward without gaps. Apply a thin coat of cement to the inside surface of the red tinsel and wrap forward with a wide gap. Wipe off any excess cement. Apply a thin coat of cement to the base of the herl and wrap forward, staying between the lines of the red tinsel. Finish with a wrap knot, cement, and allow to dry thoroughly.
This is not the most durable fly. Any time that herl is placed atop tinsel, it's an iffy proposition. But with some care in construction, the fly will last long enough to catch a number of fish before the herl breaks.
On still water, the fly is best inched along with slight twitches. It should move fast enough to keep from sinking deep, but no faster. This fly is best animated with a struggle, as if it were a terrestrial.
On moving water, drift it like a normal wet fly, keeping as much line off the water as possible and keeping drift to a minimum. The flash of the tinsel and the glow of the herl are enough to do their magic on the fish.