How to Fertilize Carnations

Provide a base of nutrients to your carnations by spreading a 2-inch-layer of organic mulch around the plants in the spring. Do not allow the mulch to touch the plant's stem because this may cause disease.

Fertilize your carnations at planting time with a fertilizer marked 20-10-20, which refers to the percentage by weight of three major nutrients: nitrogen, phosphorus and potassium. 20-10-20 is an appropriate balance to promote healthy plant growth and flower production.

Apply fertilizer again after six weeks and every six weeks during the growing season. Water thoroughly after applying to soak the fertilizer into the soil and to remove any excess fertilizer from the leaves.

Stop fertilizing over the winter, when carnations are not actively growing or flowering. Cover with a light blanket of organic mulch, which will protect the plants from winter temperatures and provide nutrients to the soil in preparation for spring.