Ivy goes through two stages in its life. It starts off in its juvenile state
as a climber with adventitious roots. It doesn't take nutrients from trees or
poison trees in any way, or do anything of that nature. Later, it enters a
mature state where it grows without adventitious roots, and bears flowers and
fruit.

Though Ivy doesn't suck the goodness out of other plants, or strangle, poison,
or in any other way actively seek to kill other plants, it does form a huge
mass of leaves that block out the sun. It competes so effectively with other
plants and grows so rapidly that many trees die from the competition.

Cutting the stems of Ivy plants where they grow up the trunk of a tree will in
most cases kill the Ivy above the point where the cut is made, but bear in moid
that unless the roots are removed, the Ivy may come back with a vengeance in a
very short space of time.

I hope this is helpful and might clear a few things up for people. All the
best for now.

Dave.