What goes down a tree but not up.?

Question:

Answers:
This is a good question and I will give you a star. The other answers are nowhere near. The answer lies within ornithology. Sounds a bit like s/mites and s/tites. the answer is of course the tree creeper, a secretive bird, little seen by the uninitiated. The tree creeper always works its way down a tree, the nuthatch always goes up
Gotcha, old Shropshire saying.

rain? i don't know!

A nut? An apple? Some other kind of arboreal fruit?

Or leaves, for that matter, in autumn.

the leaves.

apples

Sap?

Rain that is falling...

A dead monkey!

My friend Marvin once went down on a tree. He was arrested by the parks police

sap?

All those dead leaves and branches! I gave up tring to glue them back up!

An umbrella!!

Oh no, that's a chimney.

A greased monkey?

roots.