Iris (also called irises) is one of the most popular plants in American gardens. Everything you need to know about the flowering period, different varieties of the flower, and how to care for irises can be found in our overview.
As a magnificent perennial of early summer, the iris has been a popular garden plant for a long time. There are innumerable iris species and cultivars, whose flowers appear in many different colors and color combinations. Irises really do exist in all the colors of the rainbow, as their name suggests. “Iris” comes from Greek and means “rainbow”.
Iris: Flowering Time, Origin, And Characteristics
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Irises are a plant genus in the iris family (Iridaceae) and have been in our gardens for centuries. Even if their name suggests otherwise: Irises are only distantly related to lilies. The many iris species are common in the temperate zone of the northern hemisphere.
The probably best known and most intensively cultivated iris species is the bearded iris (Iris barbata). Three groups can be distinguished according to size and flowering time. The lower a variety grows, the earlier it flowers. The Barbata Elatior group consists of large irises with a height of 60 to 120 centimeters and a flowering time from the end of May to June.
It not only has the longest flower stems, but also the largest flowers. Somewhat earlier in May, irises of the medium-high Barbata Intermedia or Barbata Media group bloom. Their stems grow to a height of 40 to 60 centimeters. The small irises of the Barbata Nana group, which grow to a maximum height of 40 centimeters, bloom as early as mid-April and are thus among the heralds of spring. They are ideal for rockeries and borders.
Less well known, but at least as elegant, is the steppe iris (Iris spuria). It grows up to 150 centimeters high and can be combined well with the somewhat smaller meadow iris (Iris sibirica). With a flowering period from February to March, the dwarf iris species Iris reticulata and Iris danfordiae are among the earliest iris species. The Japanese marsh iris (Iris ensata) decorates the edges of ponds in various colors ranging from pink to blue and violet and grows to a height of 80 to 100 centimeters.
The iris flowers are composed of 3 inner and 3 outer petals. The inner petals of the bearded iris are folded upwards and closed. They form the “dome”, which in other iris species appears less strongly developed and lower. The 3 outer hanging leaves hang down at the sides. The outer leaves of the Beard Iris are also provided with a brush-like structure, the “beard”, in the upper part.
All mentioned irises have narrow, sword-shaped, and upright leaves. They are usually strong green to grey-green colored and sometimes show a slight bluish shimmer. Depending on the species irises have tubers, rhizomes, or bulbs as storage organs.
Iris Varieties: The Most Beautiful Irises For The Garden
The above-mentioned species cover a wide range of varieties. These are the most beautiful irises for the garden:
High Bearded Iris (Iris Barbata Elatior Group)
- Kupferhammer: Robust and flowering variety from 1930; yellow dome, mahogany red hanging leaves, marbled in the middle, beard in orange; height: 40 cm; flowering time: May – June.
- Provencal: Bordeaux red, hanging leaves with the yellow center; height: 85 cm; flowering time: May – June.
- Proud Tradition: Delicate purple cathedral, hanging leaves in a strong purple-blue; height: 100 cm; flowering time: May.
Medium bearded iris (Iris Barbata-Intermedia or Iris Barbata-Media group)
- Arctic Fancy: White, slightly marbled ground with a violet edge; height: 50 cm; flowering time: May – June.
- Swizzle: Golden yellow flowers; height: 50 – 70 cm; flowering time: May – June.
- Con Brio: Dark purple hanging leaves, light purple dome; flowers are fragrant; Height: 60 cm; Flowering time: May and September.
Low Bearded Iris (Iris Barbata Nana group)
- Little Buccaneer: Maroon-red flowers, yellow beard; height: 25 cm; flowering time: April – May.
- Church Stoke: Violet cathedral, violet hanging leaves (the color becomes somewhat stronger towards the center), yellow-white beard; fragrant; height: 25 cm; flowering time: April – May.
- Soft Air: White-yellow flowers; height: 30 cm; flowering time: April – May.
Steppe Iris (Iris spuria)
- Betty Cooper: petals in the middle lemon yellow with fine, lavender-colored lines, surrounded by a pale purple edge; height: 120 cm; flowering time: May – June
- Archie Owen: Bright golden yellow flowers; Height: 90 – 100 cm; Flowering time: June.
Meadow iris (Iris sibirica)
- Butter and Sugar: Cathedral leaves sugar-yellow, hanging leaves butter-yellow; height: 40 – 60 cm; flowering time: May – June.
- Caesars Brother: Small dark purple flowers; height: 60 – 100 cm; flowering time: May – June.
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- Iris reticulata Harmony: Small reticulated iris with delicate cornflower blue petals, marbled yellow and white towards the center; height: 10 – 15 cm; flowering time: February – March.
- Iris histrionics Katharine Hodgkin: Petals with light blue veins on a white background, yellow zone with dark blue spots towards the center; height: 15 – 25 cm; flowering time: March – April.
Japanese marsh iris (Iris ensata)
- Galathea: cathedral leaves rather short and delicate, hanging leaves very broad and often with pretty veins; white-purple flower; height: 80 cm; flowering time: June – July.
Iris Care: How To Care For Irises Before And After Flowering
How to plant irises correctly and which location is best for which species can be found in our special article on iris planting. Below you will find some tips on cutting and fertilizing the iris. Especially tall varieties should also be supported during the flowering period.
Iris flowers should be cut off after the flowering time for several reasons. On the one hand, this avoids energy-intensive seed formation, on the other hand, it prevents fungi and diseases. Cut the withered iris back to about 10 centimeters. The leaves can be left standing, they are also decorative elements in the perennial bed in winter. If fungi appear, the leaf lobes are also cut back and the plants shoot new leaves in midsummer. Some iris varieties such as the High Beard Iris ′Total Recall′ or ′English Cottage′ react to a consistent pruning after the first flowering with a second flowering phase in autumn.
Modern iris varieties need more nutrients than older varieties. You should fertilize the iris at least once a year. The right time for fertilization is in March when the perennials start to sprout. Second fertilization can be done in May. It is best to choose a fertilizer with a high caliber. This covers the nutrient requirements of your irises in the long term and supports their development into healthy and resistant plants.
Young iris flowers should be watered from time to time. Older plants that have established themselves well in their location do not usually need watering. However, in the event of a prolonged drought, they should be provided with some water to be on the safe side.
Most iris species are hardy and can survive the winter months without additional protection in the garden. However, some species, such as meadow iris, are more sensitive to cold and should be prepared for winter. Cut the flower stems about 10 centimeters above the rhizome and remove discolored leaves and dried leaf tips. In autumn, cover the iris with a layer of leaves, brushwood, or straw to prevent it from being exposed to frost.
One way to propagate iris is to divide the rhizomes in spring or after flowering. Even if you do not necessarily want to propagate irises in your garden, this measure is advisable. Irises often lose their blooming strength after 3 to 5 years. By dividing the rhizomes, the perennials are naturally stimulated to form new iris flowers.
Iris division: Step-by-step guide
- Date: Late summer.
- Carefully dig the rhizomes out of the earth.
- Cut through the rhizomes with a sharp knife at the visible constrictions (cut surface should be as small as possible).
- Shorten the leaves by about half (this reduces evaporation and prevents the weakening of the plants).
- Select the young, vital rootstocks (the edge pieces are the strongest) and replant fist-sized pieces.
- Water vigorously.
As an alternative to root division, which produces pure irises, irises can also be propagated by sowing. Wait until the capsule fruits are ripe and then harvest the seeds. Irises are cold and dark germination. Therefore put the seeds in the refrigerator a few days before sowing.
Then they can be sown in a protected place in growing containers filled with substrate and covered with a layer of soil about 2 centimeters high. With continuous humidification and a temperature of about 15 °C, the iris seeds germinate and develop into new plants.
Are irises poisonous?
All parts of the plant, but especially the roots of the iris, contain poisonous substances that cause serious symptoms of poisoning when consumed. They can sometimes cause skin irritation or even dermatitis when touched. For safety reasons, the iris should therefore be planted in a place inaccessible to children and pets.
Planting Iris: Time, Location, And Procedure For Planting
If you want to plant decorative irises or irises, you should first choose the right time and location. We will show you what is important and why the iris’ survival organs play an important role in the location.
Iris Planting: The Perfect Time
The ideal time to plant the iris is between July and October. But also late plantings in November or spring plantings in March are possible.
The Right Place To Plant Iris
Iris plants love the sun and should be planted in full sun, warm location. There are two types of iris, based on their survival organs:
- Bulb iris: It is known by this name, although in reality, it does not form bulbs at all but tubers. Onion iris species require a lot of moisture.
Rhizome iris: It has rhizomes as organs of survival. Rhizome irises prefer rather dry to normally moist soils and are sensitive to too much moisture.
- Therefore, when buying irises, pay attention to which outlasting organs are present. Both the bulbous iris and the rhizome iris thrive in a loose, permeable, humusy, and nutrient-rich garden soil. But irises are also well suited for rock gardens.
The marsh iris (Iris pseudacorus) and the Japanese marsh iris (Iris ensata) have somewhat different location requirements, as their names already suggest. They need moist soil, wet in spring, to thrive. They feel comfortable both at pond edges and on loamy soils.
How To Plant The Rhizomes And Bulbs Of Iris
Once the right location has been found, the earth must first be loosened up a little. To increase the permeability of the soil, you can also work some sand into the substrate or fill a layer of sand about 2 centimeters high into the planting hole, on which the iris will later be placed. Cut back the roots of the irises to about 6 centimeters in length and shorten the foliage to about 10 centimeters.
Now the rhizomes or the iris tubers can be planted. The planting distance should be 25 to 40 centimeters. Place the rhizomes or tubers flat in the ground so that about a third of them can still be seen. The irises need light to grow well. Fill the planting hole with soil and press them down well. Afterward, supply the iris well with water.
Smaller irises in particular are also very well suited as potted plants on the balcony or terrace. Choose a suitable pot with a drain hole so that excess water can run off during watering and no stagnant moisture is created.
In addition, you can place broken clay fragments on the bottom of the plant pot or work some sand into the soil. Once the irises are planted, the young plants need regular watering until they have grown well and established themselves in their location.