What does the word “Fertigate” mean ? It is known among farmers, but you will not find it in your computer’s thesaurus. Fertigate comes from fertilizer. To fertigate (Fertilize + Irrigate) means to water a plant with a mixture of plant food and water. When you use inert growing media such as GRODAN, you always “fertigate” the product, you don't just use plain water.