I love growing perennials and I use Osmocote on all my perennials in pots and in the ground. The Osmocote is an all purpose complete fertilizer with both macro and micro nutrients plus minerals so it provides the different types of plants with all they need. The recommended rate is 3 tablespoons per each 2 gallon pot and you should apply to the top of the soil then mix it into the top one inch of the soil and water well. You can use the same Osmocote on indoor plants but at half the rate. Now those are the official instructions on the fertilizer label but I no longer measure as I know how 3 tablespoons looks on top of the soil of a 2 gallon pot. So I just shake out the granules around the base of the plants either in the ground or in pots and work it into the soil or even put a bit of mulch on top of the fertilizer after I apply it. The fertilizer really does last for six months. Now for the size of the container, it is not the width but how much soil it holds. If you need 3 tablespoons for a two gallon container than 1.5 for a one gallon container and for a container that holds half that amount of soil use half the amount of Osmocote so a small four inch pot that holds two cups of soil would need about one teaspoon of product. Once you get the hang of how much the proper dose looks on the soil you will be able to just sprinkle away without measuring.   Of course I learned not to use too much - the slow release formula means the plants will not burn or turn brown if you overdose them but my roses grew too tall and leggy and flopped over with an abundance of blooms when I accidentally over dosed them with Osmocote. Some perennials with gray foliage and many sedums do not like a lot of fertilizer so I use the Osmocote at half strength on lavender, lamb's ear and sedums and succulents. Now enjoy those perennials and Keep Growing, Marianne Binetti