Some of the ivy vines might need a bit of help to become more pliable to wrap around the shape. See the detailed Tutorial below for instructions on how I manipulate twigs.

Draw a large Christmas tree shape on cardboard

This will be the outline shape of your Ivy vine tree

Cut out the shape.

Strip the Ivy vine

See the detailed Tutorial below for instructions on how to strip stems for weaving

Wrap the ivy vine around the cardboard

Secure each new stem by latching in to the previous stem

Follow a wild, random pattern crossing over the shape

Each new twig wrapped over the previous stem to secure it in place

Pay special attention to the outlines of the shape

Set the tree shape aside for the twigs to dry and shrink

Dunk the cardboard shape in a tub filled with warm water

Let the cardboard soak up the water to become soggy

Rip away the cardboard leaving the dried vine in place

Work carefully not to break the vine

Lift the ivy vine shape from the water

Weave in fresh vine to fill in any gaps to complete the Christmas tree shape

The Ivy vine Christmas tree is now ready to design with 

Источник: https://www.christinedebeer.ca/tutorials/ivy-vine-christmas-tree-mobile