BigEddy, form Ontario, Canada made the following contribution and at that a brilliant one:
Okay - if the blower / suction solution isn't what you are looking for, how about modelling it after a slinger truck?
Conveyor belt extending out 10' say, from a V Shaped hopper that mounts in place of the bucket. Using a pivot mechanism, you can get some sideways travel, or with the PT articulation you can also "turn" the belt to another spot.
Assuming you have hyro flow to the front, I'd use a hydraulic motor to drive the belt. Drive forward until the end of the conveyor is over the flower bed, engage the conveyor and "sling" some mulch onto the bed. Pivot the PT or move forward and back to distribute.
Or for better control, mount a remote valve at the end of a pivoting conveyor, then get off the seat (ugh) and stand at the conveyor, and control the position and flow from there.
Topdressing Machine improvements Power Trac, Acrease Wing mowers addict