[header] How to know what fertilizer to use on your garden plants and when to use it [title] Decide between organic and conventional fertilizer. [step] A broad and important choice you'll be confronted with is whether to use organic or inorganic fertilizer. Fertilizer not marked as " organic " is typically petroleum-based, and should not be used in organic gardens. 
Organic fertilizer can come from many sources, including animals (e.g. manure), plants (e.g.