Step 1:
This paper is for the flowers and it's red on both sides. Prefold over these 2 lines.

Step 2:
Prefold over these 2 lines.

Step 3:
Prefold over these 2 lines.

Step 4:
Now the paper has a prefolded texture with squares. Fold in half over this line.

Step 5:
Valley-fold the spot indicated by the arrow on the right to the spot indicated by the arrow on the left.

Step 6:
Mountain-fold over this line.

Step 7:
Valley-fold the edge on the left to the edge indicated by the arrow on the right.

Step 8:
Mountain-fold over this line, the edge indicated by the arrow on the left goes to the edge on the right.

Step 9:
Prefold over this line, fold the edge below to the edge indicated by the upper arrow. Then unfold the model.

Step 10:
Valley-fold over these prefolded lines.

Step 11:
Start with the 2 valley-folds below. Work clockwise from the line on the left and counter-clockwise from the line on the right.

Step 12:
Make an inside reverse fold over these 3 lines.

Step 13:
Repeat step 12 on the other 4 edges.

Step 14:
Press the 4 edges between the 2 green arrows against each other.

Step 15:
Now I'm holding the 4 edges between my fingers. Valley-fold them to the right over this line.

Step 16:
Valley-fold over these 3 lines.

Step 17:
Turn the model.

Step 18:
Open the petals with your fingers.

Step 19:
Mountain-fold over these 4 lines.

Step 20:
Make enough of these flowers for one tree.

Step 21:
This leaf paper has the same size as the one for the flowers. Prefold over these 4 lines. Then turn the paper.

Step 22:
First valley-fold over the 2 lines at the bottom-right.
Then mountain-fold over the 2 lines in the middle. Then valley-fold over the 2 lines at the top-left.

Step 23:
Valley-fold over these 2 lines.

Step 24:
Unfold the folds of step 23.

Step 25:
Valley-fold the end at the bottom of the arrow upwards.

Step 26:
Push/press the edges flat, see arrows.

Step 27:
Valley-fold the flap downwards.

Step 28:
Repeat steps 23 to 27 on the backside.

Step 29:
Rotate the model and hold it the same as I do in the next piture.

Step 30:
Make an inside reverse fold over these 3 lines.

Step 31:
Valley-fold the petal downwards. Then press the place indicated by the arrow flat.

Step 32:
Valley-fold the petal straight upwards.

Step 33:
Squash-fold the petal.

Step 34:
Turn the model.

Step 35:
Valley-fold over these 2 lines.

Step 36:
Mountain-fold over these 4 lines. Then turn the model

Step 37:
Make enough of these leaves for one complete bonsai tree

Step 38:
These papers are for the branches (small and bigger branches). The paper on the left has the same size as the papers for the flowers and leaves. The paper on the right has half that size.

Step 39:
Valley-fold in half.

Step 40:
Valley-fold in half.

Step 41:
Valley-fold in half.

Step 42:
Valley-fold in half.

Step 43:
Curl/bend the branch to make it more realistic. Make the smaller branches the same as above.

Step 44:
Glue the parts together, see arrows.

Step 45:
Glue one or more leaves to the branches. This leaf is glued in the opening edge of the branch, see arrows (just an example to make the glueing more easy)

Step 46:
Valley-fold the leaf in the right direction

Step 47:
This part is glued to the main-stem later.

Step 48:
Roll 5 a4-papers up together.

Step 49:
Valley-fold the top in half over the length.

Step 50:
Roll tape around the top and other places.

Step 51:
Wrap brown paper around the main-stem.

Step 52:
Press the top flat from all angles.

Step 53:
Crumple the other parts in your hand, see my left hand in this picture

Step 54:
Roll tape around the top.

Step 55:
Pull the edges at the bottom of the main-stem outwards, see arrows.

The main-stem is placed in a pot with florist-foam or large paper balls. Then
small black paper balls are placed on top of it. Finally the smaller branches
are glued to the main-stem.

This origami video has instructions for making the Bonsai Flower Tree: