I use Miracle-Gro Bloom Booster which has the basic NKP of 15-30-15 plus trace amounts of Boron, Copper, Iron, Manganese, Molybdenum, and Zinc. Also, I add about two heaping tablespoons of Epsom Salt.
Sta-Green has a granular lawn fertilizer with NKP of 18-24-6 plus trace amounts of Boron, Copper, Iron, Manganese, Molybdenum, and Zinc. It is much cheaper than MG but is not water soluble for sprayers. I use both at different times of the year. The granular type is better for fall applications. Many people recommend the straight 12-12-12 or other various ratios but they do not feed as well as ones with trace elements.
The important parts of both fertilizers are the trace elements. All plants need them for best growth and they can be depleted over time. I think that is a major reason why peonies and iris should not be replanted in the same soil unless it has rested for a couple of years. But, again, different areas have completely different soils and nutrients so there is no one best way to garden.
