Dietes
( dy - EE - teez )
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At-A-Glance InformationThese herbaceous perennials that grow from rhizomes are commonly called Fortnight Lily, Wood Iris, Butterfly Iris, Japanese Iris and African Iris. These plants are native to the African continent and Australia, and need full sun or partial shade (depending on the climate) and moderate to regular water. African Irises produce fans of narrow evergreen leaves and flowers appear on branched stalks in spring summer, falling on two-week intervals. Flowers come in white, cream and yellow with contrasting blotches of orange, yellow, or brown. Each flower lasts only one day. They are fantastic in pebbles and rocks and amongst shrubs and other long-lived perennial plantings in borders. Take care when planting Dietes in your garden, as some species can be poisonous to humans and animals, and can also cause skin irritation in susceptible individuals.
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Dietes Species and Varietals
There are six species included in the genus Dietes, which is a member of the plant family Iridaceae. African Iris grows best in zones 8, 9, 12-24, H1 and H2. To find your zone, click here: Zone Map.
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Dietes bicolor (African Iris, Fortnight Lily, Yellow Wild Iris) Native to South Africa, this plant produces 2-3 foot tall stems topped with light yellow flowers that have blotches that range from maroon to dark brown. Flower stems last one year and then die back to the ground. This is a particularly drought-tolerant species for the genus. |
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Dietes grandiflora (Dietes iridioides 'Johnsonii') (Fortnight Lily, Large Wild Iris, African Iris, Fairy Iris) Also from South Africa, this plant grows to 3 feet tall and has brown-marked bases of inner flower segments. Blooms are light yellow, and also have tufted darker yellow sections. Flowers last for about three days before expiring. Cultivars include 'Variegata' (with creamy yellow margins on leaves), and 'Sunstripe' (with yellow-striped leaves). |
Dietes Hybrid Species
Hybrid species include those outlined below.
Hybrid species include those outlined below.
'Lemon Drops'
Ivory blooms with yellow-orange blotches. |
'Orange Drops'
Ivory blooms with orange blotches. |
'Jack Catlin'
1.5 to 2 feet tall and 3-4 feet wide, with dark green foliage. White flowers have yellow markings. |
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Dietes iridioides (Dietes vegeta, Moraea iridioides) (African Iris, Fortnight Lily, Morea Iris) This species hails from East Africa, and produces 3 foot tall stems topped with white flowers with yellow-orange blotches. Style arms are violet. Deadhead individual flowers, not stems, until after one year. A popular variety is 'John's Runner', which has white flowers marked with yellow and purple and only grows to about 1-2 feet tall and 2-3 feet wide. |
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Dietes robinsoniana (Lord Howe Wedding Lily) This species is endemic to Lord Howe Island in Australia, and is the largest species in the genus Dietes. Leaves are long, green, and strappy, and plants can reach up to just under 5 feet tall. Flowers bloom from September to December in the plant's native range. Flowers are white with yellow. |
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Caring for Dietes
Dietes can be planted as rhizomes or nursery specimens, though rhizomes are not typically available year-round. Dietes, or Wood Iris, should be grown in a space in the landscape that receives full sun. These plants can be grown in partial shade, but will flower and grow more rapidly in a place where they receive 6-8 hours of direct sun each day. Dietes enjoys soils that are rich in nutrients, well-draining, and that have a pH of between 6.0 and 8.0. If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Dietes can be planted either in-ground or in containers, though they do better in the ground, as their rhizome roots will grow over time, and eventually overwhelm their pot. After planting, apply a thick layer of mulch around the area to suppress weed growth, maintain soil temperatures, and increase moisture retention.
Water newly installed plants regularly as they establish a strong root system. Once established, their rhizome roots allow them to get by on little water, needing only supplemental irrigations during months with no rainfall. Each year in springtime, apply a 2-inch layer of organic compost around the planting area to improve soil structure, drainage, and nutrient load. This feeding should be sufficient to provide these flowers with enough nutrients to get through their growth and flowering seasons with ease. Pruning is not necessary, but if any foliage is becoming unsightly, it can be removed at any time during the growing season. Spent flowers can be removed to neaten up the look of plants and encourage more blooms to pop. If propagating these plants via seed, the flowering stalks will need to remain and seed heads will eventually mature, providing seeds for the next generation of plants. Dietes will need dividing every few years to maintain good health and airflow around plants. They form clumps over time, and have the potential to outgrow their space. Clumps can remain in place for a while, but should be divided in fall or winter every few years for best results. for instructions on dividing Dietes plants, see the Propagation section below.
Water newly installed plants regularly as they establish a strong root system. Once established, their rhizome roots allow them to get by on little water, needing only supplemental irrigations during months with no rainfall. Each year in springtime, apply a 2-inch layer of organic compost around the planting area to improve soil structure, drainage, and nutrient load. This feeding should be sufficient to provide these flowers with enough nutrients to get through their growth and flowering seasons with ease. Pruning is not necessary, but if any foliage is becoming unsightly, it can be removed at any time during the growing season. Spent flowers can be removed to neaten up the look of plants and encourage more blooms to pop. If propagating these plants via seed, the flowering stalks will need to remain and seed heads will eventually mature, providing seeds for the next generation of plants. Dietes will need dividing every few years to maintain good health and airflow around plants. They form clumps over time, and have the potential to outgrow their space. Clumps can remain in place for a while, but should be divided in fall or winter every few years for best results. for instructions on dividing Dietes plants, see the Propagation section below.
Propagation
Dietes, or African Iris, can be propagated either by division or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Dietes flowers, follow the instructions below:
Propagating Dietes by Seed
Propagating Dietes by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost and pots (12 inch pots will do, and these are only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:
Propagating Dietes by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
- In either late winter or early springtime, get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-3 months from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Propagating Dietes by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost and pots (12 inch pots will do, and these are only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:
- Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the rhizome root(s). Once you have worked it up out of the ground, lay it out.
- Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick rhizome section attached.
- Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
- Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.
Dietes seed pods remain on flowering stalks after petals fade away.
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Dietes seeds are small and brown to dark brown in color.
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Problems and Pests
Dietes plants are susceptible to developing issues with the following pests and diseases in the landscape:
- Crown or Root Rot
- Rust
- Btrytis Blight
- Fungal Leaf Spot
- Aphids
- Iris Borers
- Nematodes
Gallery
These plants provide beautiful flowers as well as architectural foliage to this rock garden.
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Dietes plants are often seen growing in clumps or colonies.
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Here, Dietes adds some mid-level height to a border under a small tree and behind a row of Moses-in-the-Cradle.
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While Dietes can be grown in partial shade, they will flower better in full sun.
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This bed is filled with Dietes, Jerusalem Sage, and Brazilian Verbena.
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Videos
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Learn about these easy-care ornamentals.
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Check out the different types of Dietes in this bed.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 289, Dietes
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