Flag Iris Care: Information About Growing And Caring For Yellow Or Blue Flag Iris

Flag Iris Care: Information About Growing And Caring For Yellow Or Blue Flag Iris

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By: Susan Patterson, Master Gardener

If you’re looking for an interesting, moisture-loving plant to add to the garden, consider planting flag iris. Both growing conditions and flag iris care are relatively easy undertakings that will reward you with beautiful blooms each year.

What is a Flag Iris?

Flag irises are very hardy perennial plants that survive with minimal care and generally bloom in the spring and early summer. Flag irises are most often found in wet, low-lying areas and are suitable for similar conditions in the home garden. There are many varieties of flag irises, including dwarf and tall types. The most common types of flag iris plants familiar to most people include blue flag iris and yellow flag iris.

  • Blue Flag Iris – Blue flag iris (Iris versicolor) is a beautiful semi-aquatic plant. Deep green foliage and striking blue-violet flowers appear on 2 to 3 foot (.6 to .9 m.)stalks in late spring to early summer. Leaves are narrow and sword-shaped. There are many species of blue flag iris and native plants are found along the edges of swamps, wet meadows, stream banks or in forested wetlands. This hardy plant adapts well to the home garden and is very easy to grow.
  • Yellow Flag Iris – Yellow flag iris (Iris pseudacorus) is a perennial plant that is native to Europe, North Africa, Great Britain and the Mediterranean area. Yellow flag iris is prevalent all over North America, apart from the Rocky Mountains. Generally found along wetlands, streams, rivers or lakes in shallow mud or water, this hardy plant will also tolerate drier soil and high soil acidity. Gardeners often use this iris as an ornamental pond plant, and value the yellow flowers that bloom in the summer. However, it can quickly become invasive, and gardeners must beware of this in order to provide the most appropriate flag iris care.

Planting Flag Iris

The best place to plant blue flag or yellow flag iris is in a wet location that gets full to part sun. The plant can also be submerged in water for a time and still survive. Space plants 18 to 24 inches (45.7 to 61 cm.) apart.

Flag Iris Care

Flag irises do best in highly organic soil. Amend your garden area with compost or peat for best results.

Provide a dusting of bone meal when you are planting flag iris.

Be sure to water your plants liberally if the soil begins to dry out. Although flag irises are hardy and will tolerate spells of dry weather, they prefer to be moist. Provide a 2-inch (5 cm.) layer of mulch to protect plants and help retain moisture.

Propagate plants by division right after flowering every two to three years to keep under control.

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Planting Flag Iris - Learn About Growing Flag Iris Plants In The Garden - garden

Irises are a large group of fabulously colourful garden plants. Their brightly coloured flowers often have petals in different colours or with different coloured markings, producing exquisite colour effects.

The summer-flowering bearded irises or flag irises are probably the most popular and best known – with their large, bold flowers and evergreen, sword-like leaves – but there are also some fabulous bulb irises. Many of these flower in late winter and spring – making them essential garden plants. There are even irises for growing in ponds, around ponds and in bog gardens.

Among the bulb irises, the most popular is the ‘Reticulata’ group, short plants that flower from late winter. They are excellent rock garden plants and for growing at the front of borders and beds. They can also be grown as indoor pot plants – planting 6 bulbs in a 12.5-15cm (5-6in) pot – and will flower in mid to late winter.

The Dutch, Spanish and English bulb irises flower in summer, the Dutch irises being the first to do so.

How to grow irises


All irises prefer a sunny position.

Flag and bearded irises

These irises prefer a fertile, well-drained neutral or slightly alkaline soil. They are also ideal for growing at the base of a sunny wall.

Bulb irises

These irises prefer a fertile, well-drained, slightly alkaline, light soil. Add lots of organic matter to the soil when planting and even add sharp sand or grit in heavy soils to improve drainage.

Aquatic and bog irises

These will tolerate lightly shaded positions and need permanently moist or even wet soils.


Flag and bearded irises

There are literally hundreds of different varieties of bearded irises in a wide range of flower colours and heights. These range from Dwarf Bearded, growing 15-25cm (6-10in) high to Tall Bearded, growing up to 1.2m (4ft) high.

There are several specialist nurseries, which provide full descriptions and excellent images of the flowers, to help you decide which ones to grow. These include Claire Austin Hardy Plants and Cayeux.

Bulb irises

Reticulata Cantab (pale blue), Iris danfordiae (yellow), George (purple), Harmony (royal blue), Joyce (sky blue), Katharine Hodgkin (pale blue)

Dutch Discovery (violet blue), Purple Sensation (purple), Symphony (yellow), White Excelsior (white and yellow)

English King of the Blues (dark blue), Mont Blanc (white), Queen of the Blues (bright blue)

Aquatic and bog irises

These include Iris pseudacorus with yellow flowers in May and June, Iris sibirica with blue flowers in June and July, and Iris kaempferi with purple/blue flowers in June and July.

Planting irises

Flag and bearded irises

These can be planted in spring or, better still, between July and mid-October.

If your soil is heavy clay, add coarse sand and bulky organic matter to improve drainage. The ideal pH is 7 (neutral), although not essential, so add garden lime to acidic soils, which is also good to improve clay soils.

Bearded irises are generally planted 30-40cm (12-16in) apart.

These irises must be planted so that the top of the rhizomes is slightly exposed above soil level and the roots are spread out facing downward. After planting, water in thoroughly to pack the soil around the roots.

Bulb irises

Dry Reticulata iris bulbs planted in autumn often fail to grow or don’t perform very well because they may have dried out too much. It is usually better to buy potted plants.

Always improve the soil with lots of added organic matter, such as compost, well-rotted manure, composted bark or planting compost.

Reticulata: plant 10cm (4in) deep, 10cm (4in) apart Dutch and English: 5-7.5cm (2-3in) deep, 15-23cm (6-9in) apart.

Aquatic and bog irises

Plant in soil that remains permanently moist. Add lots of organic matter, such as compost, well-rotted manure, composted bark or planting compost, to help maintain soil moisture.

In ponds, it is easier to plant using pond plant baskets.

Suggested planting locations and garden types

Flower borders and beds, patios, containers, city and courtyard gardens, cottage and informal gardens, ponds, bog gardens.

How to care for irises

Flag and bearded irises

Newly planted bearded irises need watering to help them establish. After that, they rarely need to be watered except in extremely hot, dry summers. It is always better to underwater than overwater, as too much water can induce rot.

Feed with a balanced or high potash general granular plant food in early spring and then again after flowering. Avoid using high nitrogen feeds as this can encourages rot problems.

Cut back the flower stems to their base after flowering.

Remove any diseased or brown leaves when you see them, and in autumn, cut off any old or dying leaves.

Old clumps of irises should be divided every 3 to 5 years in July or after flowering before they become overcrowded and flowering is affected. Carefully lift the fleshy rhizomes with a garden fork. Select the largest fans of leaves with the healthiest rhizomes and cut these from the main plant with a sharp knife. Don’t bother with the smallest fans or very old or rotten rhizomes. Cut the leaves back horizontally about 15cm (6in) above the rhizome and trim back old and damaged roots.Dig a hole, large enough for the rhizome and roots – the rhizome should be placed at soil surface on heavy soils, a little below on light sandy soils – and firm the soil around them.

Bulb irises

The bulb irises are easy to look after and rarely need watering when growing in the ground, unless the soil dries out during prolonged dry periods.

Give them a light feed with a granular general plant food after flowering. Watering with a liquid plant food after flowering and until the foliage starts to die down will help build up their strength and size for the following year’s flowering.

Allow the foliage to die down naturally.

If the bulbs have been growing in the same soil for several years and no longer flower profusely, lift them after the foliage has died down, carefully split them into smaller clumps and replant at the same depth in soil that has had lots of bulky organic material and slow-release feed added. Only do this when absolutely necessary, as the plants dislike disturbance and should be left for 4 to 5 years at least.

Dutch irises may need winter protection with a cloche or similar covering during hard winters.

Choose and prepare your iris flower beds now for July planting

Our earliest bearded irises have started blooming just in time to add color to the garden as the last of the spring flowering bulbs are fading. As such, they occupy a valuable niche in the flower garden timeline.

Other iris varieties in our garden are forming flower buds and will begin to bloom in succession continuing the iris season well into June.

Generally, irises are fairly easy to grow, even for beginning gardeners. That holds true only if they are planted in the right spot. If placed in the wrong spot, they will never grow properly and will be a source of aggravation.

Unlike many other plants, irises are planted in July or early August. However now is the time to choose and prepare your iris growing area.

Irises absolutely require over eight hours of full sunlight. If you don’t have a spot that is exposed to that much daylight, it’s probably best not to even attempt to grow them. They’ll never gain enough energy to grow well, much less produce flowers.

The other critical requirement is very well-drained soil. I’ve found that our irises do best in the driest soil we have. If the spot you’re looking at is moist through much of the year, don’t plant bearded irises there, consider planting blue flag iris that will tolerate moist conditions.

This early yellow iris grew from a piece of rhizome dropped unnoticed along the porch where it receives no direct rain. It is significantly more vigorous than the same plant growing in a moister part of the same garden. (Photo: Bob Dluzen)

Existing perennial weeds can be a real nightmare to control in any flower garden. If you start preparing your iris bed now, you will have plenty of time to eradicate those weeds for July planting. Trying to prepare a planting bed right at planting time often yields poor results because if you miss any small pieces of perennial weed roots like quackgrass or thistle, they will sprout and grow back with a vengeance.

Be sure to allow plenty of space for your new irises, they don’t do well if they’re crowded by other plants. Crowding can cut down air circulation leading to conditions favorable to plant diseases.

Garden centers get their iris shipments at planting time so don’t look for them yet. Another popular source of iris rhizomes is other gardeners. July and August is also when irise are dug up and divided. This is done every three or four years as new offshoots grow and begin to crowd the plant. As the plants get older, gardeners will divide them to keep them vigorous. Rather than throwing out or composting extra plant rhizomes, most gardeners prefer to give them to someone who will grow and care for them.

Dwarf varieties like this purple variety are less than a foot tall. (Photo: Bob Dluzen)

Early in my career, I was given several iris rhizomes that were supposedly descended from Sir Walter Raleigh's garden. Somewhere along the line as I moved, they were left behind. I wish I still had them. They were a nice blue color as I recall, but not particularly notable. They were a great conversation starter however.

Start working on your new iris bed now a little at a time. It’ll be July before you know it and you’ll be in great shape when your iris roots arrive for planting.

Planting Flag Iris - Learn About Growing Flag Iris Plants In The Garden - garden

Variegated Japanese Flag Iris

Variegated Japanese Flag Iris

Variegated Japanese Flag Iris foliage

Variegated Japanese Flag Iris foliage

Other Names: Japanese Water Iris, Russian Iris, Japanese Flag

Attractive variegated foliage and violet flowers good for bogs or ponds as it requires consistent moisture blooms emerge from lush, sword-like foliage hardy and easy to grow cut back in the fall to reduce pests

Variegated Japanese Flag Iris features showy violet flag-like flowers with yellow centers at the ends of the stems in mid summer. The flowers are excellent for cutting. Its attractive sword-like leaves remain green in color with showy white variegation throughout the season. The fruit is not ornamentally significant.

Variegated Japanese Flag Iris is an herbaceous perennial with tall flower stalks held atop a low mound of foliage. Its medium texture blends into the garden, but can always be balanced by a couple of finer or coarser plants for an effective composition.

This plant will require occasional maintenance and upkeep, and should be cut back in late fall in preparation for winter. Deer don't particularly care for this plant and will usually leave it alone in favor of tastier treats. Gardeners should be aware of the following characteristic(s) that may warrant special consideration

Variegated Japanese Flag Iris is recommended for the following landscape applications

  • Mass Planting
  • General Garden Use
  • Bog Gardens

Variegated Japanese Flag Iris will grow to be about 24 inches tall at maturity extending to 3 feet tall with the flowers, with a spread of 24 inches. When grown in masses or used as a bedding plant, individual plants should be spaced approximately 18 inches apart. The flower stalks can be weak and so it may require staking in exposed sites or excessively rich soils. It grows at a medium rate, and under ideal conditions can be expected to live for approximately 10 years.

This plant does best in full sun to partial shade. It prefers to grow in moist to wet soil, and will even tolerate some standing water. It is not particular as to soil type or pH. It is somewhat tolerant of urban pollution. This is a selected variety of a species not originally from North America. It can be propagated by division however, as a cultivated variety, be aware that it may be subject to certain restrictions or prohibitions on propagation.

So Many Irises for the Florida Garden

Irises by Vincent Van Gogh, 1889.

Have you noticed all of the blooming irises? Their striking shapes and colors grab my attention each time. Irises are named for the Greek word for rainbow and are often called flags. Irises, both true Iris and those with iris in the common name, are not only easy on the eyes, but also easy to grow in the Florida garden. North Florida gardeners have many varieties of iris to choose from, including those that prefer wet sites, drought-tolerant species, intricate hybrids, and native species.

All irises are in the plant family Iridaceae and have six flower petals a lower set, called the sepals, or falls, and an upper set, known as standards, that are often upright. The base of the sepals, known as the signal, can have a variety of colors and patterns. Irises are clump forming plants with long, strap-shaped leaves. They need occasional dividing and propagate easy by rhizomes. Few pests bother them.

Here are a few common iris plants that grow well in our area.

African Iris blooming on January 2nd, 2018 in the Leon County Extension Office Demonstration Garden. Credit: Mark Tancig, UF/IFAS Extension Leon County.

African Iris (Dietes vegeta)

This non-native plant is not actually a true Iris but is a tough and versatile plant. Its sepals are bright white with a yellow signal. The standards are purple. This plant can be grown in full sun or part shade, from standing water to droughty conditions. It works nicely as a border or foundation planting. Flowers only last a few days but are produced throughout the year. We had one blooming in our Demonstration Garden through a cold snap this past January. Cold weather can cause leaves to turn brown or gray, requiring some maintenance to improve appearance.

Bearded Iris. Credit: Mark Tancig, UF/IFAS Extension Leon County.

Bearded Iris (Iris x germanica)

A non-native, true Iris, bearded irises are the fancy hybrids that can come in many different colors. The “bearded” refers to the many hairs along the signal. Bearded irises prefer sunny locations and bloom in spring.

Iris versicolor. Credit: Mark Tancig, UF/IFAS Extension Leon County.

Blue Flag Iris (Iris versicolor and Iris virginica)

Two species of Iris go by the same common name, blue flag iris. These two are often misidentified in the nursery trade as well. Both have purple flowers that bloom in the spring, are native, and occur naturally in wetland areas. Gardener can have easy success with these in irrigated and/or rain gardens with some light shade. To tell the two apart requires a careful look at the lower sepals, or falls. Iris versicolor’s sepal has a greenish-yellow signal (base), surrounded by a white background with dark purple veins. The sepal of I. virginica has a bright yellow signal with little prominent veining. They also both have a 3-angled fruit.

A Louisiana iris hybrid. Credit: Mark Tancig, UF/IFAS Extension Leon County.

The name Louisiana iris refers to five true Iris species – I. brevicaulis, I. fulva, I. giganticaerulea, I. hexagona, and I. nelsonii – that are native in and around Louisiana. They easily hybridize with each other and these hybrids have become popular garden cultivars. Louisiana iris prefer moist soils and full sun.

Walking Iris (Neomarica gracilis). Credit: Mark Tancig, UF/IFAS Extension Leon County.

Walking Iris (Neomarica spp.)

Another unofficial iris, most plants in the Neomarica genus share the same “walking” attribute. Small plantlets can develop at the top of the flower stalk and then fall over to start a new clump of plants. These do best in part shade to shade and have a long flowering period. They are somewhat cold tender so may die back but will return in the spring.

Yellow Flag Iris (Iris pseudoacorus)

The invasive, exotic yellow iris. Credit: Ann Murray, UF/IFAS.

This non-native Iris is one that you want to keep out of the garden. Yellow flag iris is known to invade natural wetlands and has been designated invasive by the UF/IFAS Assessment of Non-Native Plants. It’s easily distinguished from the other irises listed above by its bright yellow flowers. If you have this iris, remove fruit and carefully dig out the rhizomes, place in a trash bag, and dispose of it in your solid waste bin.

For questions regarding iris identification or care, contact your local UF/IFAS Extension Office.

Problem #5: Overcrowding

Divide and conquer! Every three to five years Bearded Iris tend to become overcrowded and the rhizomes should be divided. You’ll not only get to add Bearded Irises to other parts of your garden free-of-charge, but you'll be proactively preventing the spread of pests and disease.

Bearded Iris should be divided and re-planted every few seasons to prevent overcrowding.

Basic Steps To Divide Bearded Iris:

  1. Dig a large hole around your clump of Bearded Iris and gently pull the roots up.
  2. Wash the soil off with a hose.
  3. Cut the rhizomes apart so each section has at least one healthy fan of leaves and firm, white roots.
  4. Re-plant in different parts of the garden, making sure to leave the the newly-transplanted rhizomes partially exposed, with plenty of room to grow.

Shop Bearded Iris

Deschutes Bearded Iris casts a glow to harmonize and enhance the perennial garden. Ruffled twilight blue petals and sky-blue beards create a calm, serene presence in the late spring .

Our Reblooming Bearded Iris Collection will have you daydreaming of wide blue skies and fluffy white clouds. Spring days can fly by quickly, so you'll be pleasantly surprised when al.

Dangerous Mood Bearded Iris is a blue-lovers delight. Deep velvet-blue ruffled falls (downward petals) are lit by three upright petals (standards) of pure white blushed with indigo b.

'Sugar Blues' Reblooming Bearded Iris sparkles in the sun with its wisteria blue petals and white beard. A fragrant iris that blooms in late spring and again in early fall. Easy to g.

Watch the video: German or Bearded Iris Maintenance and Care


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