Set the next parameters for each of the three demonstrated spiral’s elements:
Blending Options>Outer Glow

We’ll get the same picture:

Download out of Internet a set of ready to use brushes for Adobe Photoshop, named GVL Funky Flower Brush

On this stage we need to represent arbitrary a composition made of different flowers of different sizes.

Give this layer the next shown parameters:

This is what we’ve got on the final stage!

View full size here.