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How to Grow Agapanthus (Lily of the Nile) Indoors or Outdoors

Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.

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If you are looking for plants to lend a tropical touch to your landscape, look no further than the agapanthus or lily of the Nile. Despite its name, it is neither a lily nor native to the Nile region.

What is Agapanthus?

Agapanthus (Agapanthus praecox) is a flowering plant that is native to South Africa. It has naturalized in Mexico, Central America, the Canary Islands and Ethiopia. It is considered invasive in Australia and New Zealand.

Agapanthus is hardy in zones 7 – 11. In the colder parts of its range, the rhizomes should be planted deeper to help them survive the winter.

This is a clumping plant that grow from rhizomes. It is quite tough and grows quickly, so it is not surprising that it has become invasive in some countries.

The foliage grows out of short stems in large rosettes of arching, long strappy leaves that are 12 – 24 inches long and 1 -2 inches wide. The foliage is attractive when the plants aren’t blooming.

Agapanthus used to be classified as an allium because its foliage and especially its flowers resemble alliums. The flowers grow on long stems. Dwarf varieties have 12 – 18 inch stems, while the rest have stems that grow 3 – 5 feet tall.

The flowers grow in umbels which are clusters of flowers which can either be flat, like Queen Anne’s Lace or rounded like alliums. The individual flowers look like lilies. Originally, the flowers were blue, but newer cultivars have been bred to have while flowers. Bloom time is mid-summer through the fall.

If you don’t want your agapanthus to spread all over your garden, be sure to deadhead the flowers, removing them before they develop seed. If you leave the seedheads on the plants, they will drop seed in your garden which will readily germinate into new plants.

Another good reason to remove the spent flowers before they become seeds is so that your plant can direct its energy into making food to be stored in the rhizome for next year. Always leave the leaves until they are killed by the frost so that they can perform this important work.

Newer cultivars have been bred to have white flowers instead of the usual blue.

Newer cultivars have been bred to have white flowers instead of the usual blue.

How to Grow Agapanthus Outdoors

Most gardeners purchase agapanthus as rhizomes. Plant the rhizomes deep enough so that they are just under the soil. In colder climates (zone 7), plant them a few inches deeper then cover them with a thick layer of mulch to protect them from the cold of winter.

Plant your rhizomes 2 – 2 ½ feet apart. If you are planting them along the foundation of your house or along a sidewalk or driveway, plant them 2 feet back from the foundation, sidewalk or driveway. The rosettes of leaves are quite large and require a lot of space.

Agapanthus grows best in full sun, which means 6 – 8 hours of sunlight each day. Morning sun only or afternoon sun only is not sufficient. It can tolerate poor soils, but well-drained soils are a must. The plants will develop root rot in wet or soggy soils.

Once the plants are established in your garden, they are drought tolerant. There is no need to water except during periods of drought. During those periods, water your plants but don’t water again until the top inch of the soil has dried out.

Fertilize your plants with a slow release fertilizer in the spring and the fall.

Be sure to set back your plants by at least two feet from paths and driveways .

Be sure to set back your plants by at least two feet from paths and driveways .

How to Grow Agapanthus Indoors in Containers

Agapanthus grows well in containers and can either be brought indoors during the winter in colder climates or even grown entirely indoors as a houseplant.

A single plant will fill a 12 inch pot. You will need a larger pot if you want to grow more than one plant in your container. Use regular potting soil with good drainage and slow release fertilizer. Plant your rhizomes just deep enough that the soil barely covers them. Only water them when the soil dries out.

Grow them in a south or southwest facing window for maximum sunlight indoors.

You can move your potted agapanthus outdoors in the spring after all danger of frost has passed. Be sure to bring them back indoors in the fall before the first frost.

Agapanthus blooms better when it is slightly root- bound. They don’t like having their roots disturbed so only divide and repot them every 4 – 5 years when the roots are pushing up out of the soil.

Individual flowers resemble lily flowers.

Individual flowers resemble lily flowers.

How to Divide Agapanthus

Agapanthus blooms best when it is crowded in your garden with roots pushing out of the soil or potbound if grown in a container. After a few years, it will be too crowded or potbound and not bloom as well. Wait until after your plant blooms to divide it.

In the garden, use a garden fork to dig up the clump of plants. Or if growing in a container, turn the container on its side and tap the bottom to loosen the soil so that the clump will slide out easily.

Using a sharp knife or pruners, cut the rhizomes into pieces, discarding any dead or diseased pieces. Make sure that each piece of rhizome has both roots and foliage. A rhizome won’t grow without roots.

Replant your divisions 2 – 2 ½ feet apart in your garden or one division per 12 inch pot. Whether growing in your garden or in a container, the divisions may not bloom the following year. They need a year to grow into their new homes before they will produce flowers.

Collect your seeds before the pods split open.

Collect your seeds before the pods split open.

How to Grow Agapanthus From Seed

Agapanthus is easy to grow from seed, but the plants will not bloom for a few years. You can collect seed from your plants. Wait until the seed pods turn brown but before they split open. Put the harvested pods in a paper bag with slits for air circulation to finish drying. When they split open, gather the seed for planting.

Start your seeds as soon as your harvest them. Plant them in a container filled with a soilless mix. If you use potting soil, the seedlings will rot. Barely cover the seeds. Place the container somewhere warm in indirect sunlight. Water just enough to keep the soilless mix moist but not soaking wet. Germination should occur in 3 – 4 weeks.

Keep your seedlings indoors for the first winter. You can plant them outdoors in your garden in the spring after all danger of frost has passed.

Your new plants should bloom in 3 - 4 years.

© 2021 Caren White

Comments

Caren White (author) on February 05, 2021:

You're welcome! I hope that you try these wonderful plants for yourself.

Pamela Oglesby from Sunny Florida on February 04, 2021:

These flowers are so beautiful Thank you for sharing so much excellent information.

Caren White (author) on February 04, 2021:

You have the perfect climate for them! They must be spectacular.

Peggy Woods from Houston, Texas on February 04, 2021:

We see a lot of agapanthuses grown here in the Houston area. Thanks for writing this informative article about how best to grow them, including from seed.