Fertilizing Annuals: The Complete Guide to Nutrients, Types, and Application

Unlike perennials, annuals have just one season to perform. Because they pour energy into flowering, proper fertilization ensures the best possible show. Learn how to mulch your annuals.

Key Nutrients for Annuals

Annuals need the big three—nitrogen (N), phosphorus (P), and potassium (K)—plus secondary nutrients (magnesium, calcium) and trace elements (boron, iron). Healthy, organically rich soil often supplies enough, but container-grown annuals lose nutrients with every watering and need regular replenishment.

Incorporate organic amendments yearly and apply a balanced fertilizer periodically. If a soil test reveals deficiencies, add the specific secondary or trace minerals recommended. For flowering annuals, use an all-purpose formula like 5-10-5 or 10-10-10; foliage plants prefer higher nitrogen (first number).

Types of Fertilizer

Whether granular or liquid, synthetic or organic, always follow package directions. Over-fertilizing causes weak, pest-prone growth and pollutes waterways.

Granular Fertilizer

Spread around plants, scratch in lightly, and water. Synthetic granules can be applied at planting and during the season. Organic granules release slowly; apply in spring before planting. Rock powders (phosphate rock, granite dust) break down very slowly—add in fall for next year’s garden.

Liquid Fertilizers

Ideal for containers. Modern liquid fertilizers (like deodorized fish emulsion) are environmentally safe. Dilute to half strength to save money and avoid overfeeding. Apply every three to four weeks, especially to potted plants.