Take a sheet of paper and make a crease as shown.
Fold these 2 opposite corners into the centre crease.
Fold the outer corners to the centre crease.
Again, fold outer corners to the centre.
Turn the model over and fold the bottom up to the top corner.
Now fold in half.
Crease, as shown, the front and the back. Now, use the creases to reverse the fold of the leaf outside.
Your stem is ready.