For what purpose? Hardy geraniums or pelargoniums? In containers or planted in the ground?

I have never fertilized hardy geraniums planted in the ground - they don't need it with any sort of decent soil. I only fertilize pellies if grown in containers. And any water soluble fertilizer will work for that purpose.......Miracle Gro is perfectly fine.

For pelargoniums, I use either all purpose Miracle Gro slow or any general all purpose water soluble.

Thanks garden gal and praire_northrose...I grow my perlargoniums in ground and in containers..I overwinter them dry in bags and have best results with the bigger plants. So I try and feed regularly. Miracle grow has worked great for me. I just heard of people using tomato fertalizer with better results..something to do with the ratio being close to 20-20-20 being the ideal formula?!

A 20-20-20 is just an increased dose of 1-1-1 (or 10-10-10) ratio. This is considered a balanced fertilizer and often referred to as "all purpose", as it can be used on anything. But most tomato fertilizers do not have this ratio - they tend to be much closer to a 3-1-2 ratio, which is the ratio with which almost all plants take up nutrients and is typically considered the "ideal" formulation. Not that there is such a thing :-))

I have never fertilized intentionally. I just stick them in the ground and water them; they spread and flower easily. I love geraniums for how effortlessly they will root from cuttings.