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How to Fertilize an Agapanthus

By Jenny Harrington

Agapanthus plants produce clusters of lily-like flowers in the summer months. The white or blue flowers form an orb of blooms atop graceful, slender stems. Agapanthus grows well as a garden plant in areas where temperatures rarely drop below 18 degrees Fahrenheit. In colder climates the agapanthus grows well in pots indoors, either year-round or seasonally. The amount and frequency of fertilizer application depends on whether the plant grows in the garden bed or a planter.

Potted Agapanthus

Dilute a 10-10-10 or similar balanced fertilizer with water at half the strength recommended on the fertilizer label.

Water the plant with the fertilizer water once monthly during the spring and summer months. Fertilizers leach from potted plants more quickly than from soil in beds, so monthly fertilizer is necessary to replenish soil nutrition.

Stop fertilizing the plant in fall and winter. Agapanthus enters a period of slow growth in winter and doesn't require additional soil nutrients. Resume fertilization in spring as the plant begins putting on new growth.

Garden Agapanthus

Sprinkle 1 cup of 14-14-14, or a similar blend, of slow-release fertilizer along every 10 feet of agapanthus row in spring as new growth begins. Apply the fertilizer the soil 6 inches away from the base of the plants.

Water the bed immediately after fertilization. The water helps the fertilizer soak into the soil where the roots of the agapanthus have access to the nutrients.

Reapply the fertilizer two months later in early summer. Make a final application in late summer or early fall, two months after the previous application. Water the bed thoroughly after each application.


Things You Will Need

  • Soluble fertilizer
  • Slow-release fertilizer


  • Fertilizer application rates vary between the different formulations. Refer to the instructions on the fertilizer bag to ensure you apply the correct amount.

About the Author


Jenny Harrington has been a freelance writer since 2006. Her published articles have appeared in various print and online publications. Previously, she owned her own business, selling handmade items online, wholesale and at crafts fairs. Harrington's specialties include small business information, crafting, decorating and gardening.