Adaptable and easy-to-grow, hostas are popular perennials for good reason. Though hostas generally take care of themselves, the plants may benefit from fertilization if grown in poor soil. The best approach to fertilizing hostas involves proper timing and takes into account the particular soil conditions where the plants are growing. Unless a soil test indicates otherwise, hostas generally only require nitrogen fertilizer, according the University of Minnesota Extension.
Get a soil test to determine what nutrients are lacking in the soil where the hostas grow. If the soil test indicates the soil has sufficient amounts of the necessary nutrients, then all the hostas will need is an application of compost each fall. If nitrogen or other nutrients are lacking, however, proceed to Step 2.
In early spring, when hosta leaves are emerging from the ground, mix the required fertilizer according to package directions. Apply fertilizer solution on soil surrounding each plant, but make sure you do not get fertilizer on the plant itself.
Water the plants two to three times within the week following fertilizer application, to ensure the nutrients go down into the soil where the roots can access them.
Repeat the fertilizer application and subsequent watering six weeks later, or just before flowers emerge.