When To Fertilize Agapanthus – Tips On Fertilizing Agapanthus Plants

Agapanthus flowers. The flower of summer which attached the petal and the bud.
Image by fpdress

By Bonnie L. Grant

Agapanthus is a spectacular plant also known as Lily of the Nile. This amazing plant is not a true lily nor even from the Nile region, but it provides elegant, tropical foliage and an eye-popping bloom. Agapanthus is a heavy feeder and does best with organic compost worked into the soil at planting and fertilizer during its growing period. Knowing when to fertilize agapanthus and what formulas to use will ensure big bountiful blooms and healthy plants season after season.

When to Fertilize Agapanthus

Agapanthus plants are not reliably hardy below United States Department of Agriculture zone 8. In protected sites, they might survive the winter but a little special Agapanthus care and feeding is necessary in spring to start them off right.

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Avoid fertilizing Agapanthus plants with high nitrogen fertilizers in spring, which will force new leafy growth at the expense of flowering. The best Agapanthus fertilizers will be fairly balanced, such as 10-10-10 or 5-5-5, or slightly higher in phosphorus than nitrogen.

Agapanthus grown outdoors will die back in winter. Spread a heavy mulch around the root zone to protect the plant from the cold. In cooler zones, dig up the bulbs and pot up the plant to grow indoors during winter. Plants outside that are dormant do not need fertilizer until they begin to sprout anew.

Indoor plants can be fertilized just as any houseplant with light dilutions of food from February until you move the plant outdoors. Outside plants should be fertilized with a mild dilution of food in early spring and again two months later. Suspend any fertilizer to either potted or in-ground plants by August.

Tips for Fertilizing Agapanthus Plants

The best fertilizer for Agapanthus should be an organic liquid formula or granular application. Make sure to water in the formula you choose when fertilizing Agapanthus plants. Soaking the area will ensure the food gets to the roots for quick uptake and prevent excess salt in soil and potential root burn.

Granular formulas should be worked into the soil around the root zone at a rate of 1 to 1 ½ pounds per 50 square feet. Liquid formulas should be diluted according to the product’s instructions.

Agapanthus doesn’t benefit from foliar feeds and it needs feeding just twice during the growing season. Some gardeners state they don’t even feed the plants, but this would be in cases where the soil is rich in organic amendments. Apply Agapanthus fertilizer in the coolest part of the day.

Agapanthus Care and Feeding

The bulbs of Agapanthus are not frost hardy and may need to be lifted or potted up for winter. Other care is minimal after feeding but consistent water is key to producing blooms. Divide the plant every fourth year in early spring.

Most pests are not a problem, but occasionally snails and slugs can plague the strappy leaves. The most common problem with Agapanthus is rot. This occurs in soils that are too heavy and don’t drain well. Amend soil with plenty of compost and some gritty matter before planting. Sometimes, rust can occur in the leaves. Water when the leaves can dry quickly and avoid overhead watering.

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