An idea that may work for you... Use a transform effect on a single leaf. You can set a number of copies on the effect and the transformations are cumulative, so you can scale, move and rotate to get the spiral effect.
- Draw a single leaf (draw it vertically, i.e. not rotated).
- With the single leaf selected go to Effect → Distort & Transform → Transform...
- Set the scale, move and rotation (also set the rotation origin to the bottom left) to something similar to the following:
Tip: If you need your transform origin to be outside of the original object you can group the original object with another larger transparent object.
Also uncheck "Scale Strokes & Effects" if you want to keep your strokes and effects uniform.
Even if you can't get the exact placement you want with the effect, you can get it close, expand the effect (Object → Expand Appearance) and manually adjust each object from there.