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How to Grow and Care for African Iris

This flower is a showstopper in any garden.

<p>Margot Kiesskalt/Getty Images</p>

Margot Kiesskalt/Getty Images

The African iris (Dietes iridioides), also known as "fortnight lily,” is a whimsical evergreen perennial that is native to southern Africa and naturally thrives in warmer climates. Its foliage grows in a fan-shaped pattern, and the leaves are sword-shaped. It's adorned with pretty, white, playful petals that have purplish blue and yellow markings.

"The name ‘fortnight lily’ comes from the fact that the plant produces flowers every fortnight—two weeks—from spring through fall," says Nathan Heinrich, horticulturist and botanical designer. "Another name often associated with African iris is "butterfly flag" because the flowers resemble the wings of butterflies fluttering in the breeze."

Needless to say, these beautiful flowers make a wonderful addition to your flower beds. Whether you live in a warm or cooler climate, you can grow gorgeous African irises with these expert tips.

How to Care for African Iris

Although the African iris is technically a perennial flower, it won't survive in harsh winter temperatures or if it's not properly cared for. These tips will help you extend the life of your African irises so you can enjoy them year after year.

Soil and Light

Melvin Cubian, a certified botanist and gardening expert for the PlantIn App, advises using friable and humus-rich soil by mixing various substrates, such as compost, perlite, and standard soil.

"African iris are very versatile when it comes to soil requirements. They will thrive in soils that range from sandy and well-drained to wetlands and swampy conditions," Heinrich explains.

As far as light is concerned, African irises love the sun. "These South African natives can handle some morning shade, but they need five or six hours of full sun every day," Heinrich advises. "In the very hottest regions, late afternoon shade is absolutely fine for these beautiful plants."

Water and Fertilizing Needs

"Once established, these iris plants are drought tolerant but prefer getting watered every few days during the growing season," Heinrich says. "If you live in an area with lots of rain throughout the year, you might never have to water your African iris."

Cubian states that fertilizer is optional if you have infused compost into the soil. However, you can still side-dress the plant to boost its flowering (look for NPK plant food with a "6-10-10" ratio on the label).

Temperature and Humidity

The African iris is a relatively cold-hardy plant and very tolerant of high summer temperatures. "They grow in Zones 8 to 11," Heinrich says. "However, in the case of severe frost, they can die back to the roots, but they will regrow when the weather warms up."

Since it's best to keep African iris at warmer temperatures, it's best to bring them indoors if they're in pots. "Ensure your plant sits in a comfy spot where you don't feel cold or hot. Its ideal temperature is between 65-85 F," Cubian advises.

Pruning

Heinrich says that you should not prune your African iris by hacking its graceful swaying leaves in half. "In California, where I am from originally, these irises are often found in commercial real estate landscapes, and the landscape maintenance crews regularly ‘shape’ these elegant grass-like plants into rounded mounds the same way one might shape a boxwood," he says. "This is not the right way to tend to an African iris."

Heinrich advises that you should ensure you have enough room for African irises before you plant. "These plants can grow to 3 feet tall and 3 feet wide at maturity," he says. "The only thing you would ever need to 'prune' on one of these plants is dead leaves or frost damage from cold weather."

“The most effective way to control the size of your African iris is to divide it when it gets too large," he adds.

Propagating

Heinrich says there are two ways to propagate African iris. "The first way is to divide them, which can be done quite easily," he explains. "They grow on rhizomes, and a single mother plant can produce dozens of baby plants."

He continues: "You can also propagate easily from seed. Seed pods form on the old flower spikes, and these can be collected. The seeds sprout in seed trays and are transplanted once they are approximately 3 feet tall."

However, he says you will need to remove the seed pods before they open if you don't want your African iris to self-seed.

Growing in Pots

"While you can grow African iris in pots, I don't recommend it unless you are prepared to divide them regularly," Heinrich warns. "These plants multiply quickly and will rapidly outgrow your containers."

There is one exception, however. Heinrich says it does make sense to grow African iris in containers if you live in a cold climate, as this allows you to move them into a protected area during severe temperature drops.

Cubian says if you grow in pots, you should sow the seeds approximately an inch deep in early spring after the last anticipated frost date if your pots are outdoors. You should keep the soil moist until they germinate in four weeks. He also advises placing them in a spot with direct sunlight, such as window sills.

Overwintering

Since African irises grow best in USDA gardening zones 8-11, they will grow as an annual flower if you live in a colder region unless you overwinter them. If you are growing them in pots, you will want to bring them indoors before the first frost. Remember, they thrive in warmer temperatures and love full sun, so you will want to put the pots in a sunny location in your home.

If you are trying to overwinter African irises that are planted in the ground, you will have to dig up the rhizomes to overwinter them until spring, when you can replant them. Ensure you gently shake off the excess soil and allow them to dry before storing them in sand or peat moss. However, rhizomes can be prone to fungus if not stored correctly.

Common Pests/Diseases

Heinrich says that while it's rare, African iris can have issues with aphids and iris borers. The best treatment for aphids and borers is neem oil.

"Nematodes, which are common in most soils, can occasionally be an issue for African iris," Heinrich says. "These are best controlled by removing any dead leaves and keeping the plant maintained and healthy."

Here are some other common problems with African iris Cubian warns about:

  • Crown rot is common in African iris and grows in clay or boggy environments. To prevent this, it is important to incorporate compost and sand or raise the planting beds.

  • Fungal leaf spots, caused by diverse pathogen species, are also a problem. To prevent the disease, practice regular removal of dead plant debris, mulching, and direct soil watering (rather than on leaves).

  • Snails are delighted with the succulent leaves of the iris. Handpicking, beer traps, or snail pellets help keep them at bay.

Frequently Asked Questions

Do African Iris Attract Pollinators?

African iris's beautiful blooms attract butterflies and bees. They would make a great addition to your pollinator garden, which will benefit the ecosystem.

Will African Iris Spread?

African irises are similar to other irises and are spread by rhizomes. However, they also produce seed pods that can allow them to spread. Remember, dividing them from the mother plant is the easiest way to propagate.

Is African Iris Toxic to Pets?

This beautiful bloom can be toxic to cats, dogs, and horses. So, if you have pets, it's best to keep these flowers out of your home and not accessible to them outdoors.

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