Irises are some of the most beautiful and iconic flowers that grace our gardens each spring. With their distinctive sword-like leaves and stunning blooms in a rainbow of colors it’s no wonder these flowers have been loved and celebrated for centuries.
But if you’re new to growing irises, you may be wondering – what do they look like before those gorgeous flowers appear? Knowing what to expect can help you provide the best care for your irises so you get the maximum bloom.
In this beginner’s guide we’ll walk through the growth stages of the iris so you know exactly what to look for from the time you plant the rhizomes until those showy blossoms burst open.
Iris Growth Stages
Irises go through a distinct series of growth phases during the seasonal cycle. Here’s a quick overview of what you can expect:
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Fall – Irises are planted in late summer or early fall as rhizomes. At planting, an iris rhizome looks like a knobby, misshapen root with some leaves sprouting from the top
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Winter – The leaves die back and the rhizome goes dormant over winter. You’ll just see the bare rhizome if you peek at it during the cold months.
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Early Spring – Leaves start emerging and growing from the rhizome again. This leafy growth occurs before any flower stalks appear.
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Mid Spring – The bloom stalks emerge, elongate, and flower buds form. The unopened buds may show some color before they fully open.
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Late Spring/Early Summer – Flowers open! This is the iris bloom season most gardeners look forward to.
Now let’s take a more detailed look at what you can expect to see during the key growth stages leading up to bloom.
Fall – Planting Iris Rhizomes
Irises are planted in late summer or early autumn as rhizomes. The rhizome is a thickened underground stem that stores energy and shoots out roots below and leaves above.
Iris rhizomes are knobby and asymmetrical, often showing scars from old leaf attachments. They can range in size from smaller than a finger to as big as a large potato depending on the iris variety.
When you receive rhizomes from a supplier, they will likely be bare with no leafy growth. Some varieties may have some stubby brown leaves still attached.
Once planted in the garden, most iris rhizomes will start sprouting leaves within 2-3 weeks. Some may not leaf out until the following spring.
![Iris rhizomes ready for fall planting][]
Iris rhizomes ready for planting in late summer or early autumn.
Winter – Dormant Period
Once cold weather arrives, the leaves that sprouted from the rhizome will die back. The rhizome will become dormant over the winter months.
If you peek at your iris planting, you’ll just see the bare rhizomes resting in the ground. This dormant period is important to the iris growth cycle.
For winter protection, gardeners often add a light mulch over the rhizomes after the ground freezes. But avoid mulching too early or using heavy mulch that could cause rotting.
Early Spring – Leaves Emerge
As temperatures warm in early spring, usually March or April, new leaves will start growing from the rhizomes as they wake from dormancy.
The olive green, sword-shaped iris leaves are the first visible sign of growth. They emerge in a fan shape, with multiple leaves arising from the rhizome.![Irises showing new leaf growth in early spring][]
New iris leaves appearing in early spring before bloom stalks emerge.
Don’t worry if you don’t see flower stalks yet! The plants are focused on generating strong foliage growth first.
Leaves provide the plant with energy to support the coming blooms. More robust leaves = more flowers.
Mid Spring – Bloom Stalks Emerge
After several weeks of leaf growth, you’ll notice new stalks starting to rise up above the leaves in mid-spring. These are the bloom stalks or flower stems.
The stalks elongate rapidly, eventually towering over the foliage. Buds will start forming in bracts (specialized leaf-like structures) spaced along the upper stalk.
Bloom stalk height varies by iris variety – dwarf types may reach only 8-16 inches while tall bearded irises can grow 3 feet or taller!
As the buds mature, they will start to show some color. This gives you a sneak preview before the actual blooms open up.![Iris bloom stalks emerging][]
Iris bloom stalks elongating and flower buds forming in mid-spring.
Late Spring/Early Summer – Time to Bloom!
After weeks of anticipation, your irises will finally burst into bloom in late spring or early summer.
The buds along the stalks will open sequentially, often starting from the bottom and working upwards. If you have multiple rhizomes, they may not all bloom at exactly the same time.
Now you can sit back and enjoy the full flowering display after watching the irises progress through their earlier growth stages.
The blooms will unfurl their colorful petals to bask in the sunlight and usher in the spring season.![Bearded iris in full bloom][]
Bearded iris open in late spring, showing off their stunning colors.
Follow Proper Care Through the Seasons
Understanding the key growth phases for irises will help you provide proper care at each stage:
- Fall – Plant rhizomes at the correct depth in well-drained soil.
- Winter – Add winter mulch after the ground freezes to protect rhizomes.
- Spring – Remove mulch so new growth can emerge. Water if soil is dry.
- Summer – Avoid overwatering during bloom season and let soil dry out between waterings.
With the right conditions, your irises will progress smoothly through their growth cycle from rhizomes to leaves to bloom stalks and finally, glorious flowers!
Now that you know exactly what to look for, you can anticipate these changes and have your camera ready to capture the subtle beauty of irises at each stage.
Where to Plant Iris
Perennial Gardens Bearded iris are classic plants for perennial gardens. They bloom in early summer at the same time as roses, peonies, poppies, lupines and dianthus. Siberian iris are also good performers in a mixed perennial garden. Even when the plants are not in bloom, the upright foliage adds a strong vertical accent.
Naturalized Plantings Beardless iris are good companions for ornamental grasses, sedum, rudbeckia and other naturalistic, low maintenance perennials. As they like steady moisture, they do well planted along the edges of ponds and streams. All will thrive with little or no attention.
When the bearded iris flowers in the spring, they need water. After the flowers die down, the plants go to sleep, and the rhizomes should be kept as warm and dry as possible. Coarse, fast-draining soil is ideal. Consider planting them at the edge of a sidewalk or in a poor, gravely area.
Siberian iris in rain gardens need water to grow at first, but after a year or two, the plants can handle being dry. They will tolerate poor soil and alternating periods of wet and dry.
Cutting Gardens All iris are great cut flowers. It only blooms for one or two days, but each stem has many buds that will open in the vase.
Plan for Success
Sun or Shade: Iris flower best in full sun, though most can also be grown in dappled shade.
Zone: Iris reticulata and Dutch iris are hardy in zones 5-9. Bearded iris, Siberian iris and Japanese iris are winter hardy in zones 3-9. Louisiana iris are hardy in zones 6-9. Find your hardiness zone HERE.
When to Plant: Plant iris reticulata in fall for spring flowers. Plant other types of iris in early spring or early fall when the plants are dormant. Container-grown iris may be planted at any time during the growing season.
Bearded Iris: Also known as German iris, bearded iris bloom in mid to late spring. The flowers have upright petals called “standards” and cascading petals called “falls”. Running down the center of each fall is a “beard” that resembles a furry caterpillar.
Bearded iris have flattened, sword-like leaves. There are three different heights of iris plants: dwarf, intermediate, and tall. They can be as short as a few inches or as tall as more than three feet. Bearded iris have thick, fleshy roots (rhizomes) that grow on or very close to the soil surface. For best results, grow bearded iris in full sun with well-drained, neutral to slightly acidic soil.
Beardless Iris: The plants in this iris family include Siberian iris, Japanese iris (Iris ensata), and Louisiana iris. All have an upright growth habit, long, strappy foliage and dense, fibrous roots. They may be grown in full sun or partial shade.
Siberian iris are extremely hardy, vigorous and adaptable. They form large clumps and have grassy, upright foliage that maintains its good looks all season long. Siberian iris flowers are considerably smaller than bearded iris and bloom from late May into June. They prefer relatively acidic soil and consistent moisture, but will tolerate periods of dry weather.
Japanese iris flowers are as big as an outstretched hand. The upright standards are short and the falls are long, which gives the flowers an open look. The plants need moist soil and grow well beside a pond or stream.
The Louisiana iris flower can be as soft as a wildflower or almost as big and showy as a bearded iris flower. Plants of this type grow wild in ditches, near wetlands, and other wet places in Louisiana, Florida, Arkansas, and Mississippi. You can’t put Louisiana iris outside in the winter like you can other types of iris. They do best where it is hot and humid in the summer.
Iris Care After Flowering
FAQ
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