The fertilization routine for forget-me-nots significantly depends on the nutrient in your soil. Generally, forget-me-nots require fertilization at least twice a year.
Once in spring, when they are planted and then in the fall. Most gardeners describe early fall as the ideal time for the second cycle of fertilization.
This allows the soil to boost towards the end of the season while preparing the plants to grow strong in the next spring as well. You can also spread a 2- to 3-inch layer of organic mulch over the soil to help keep it moist. Water the plants when the top of the soil begins to dry.