How To Grow And Care For Bearded Iris
Getty images
Bearded irises (Iris germanica) are one type of iris plant distinguished by the fuzzy “beards” in the three downward falling petals. These plants grow from rhizomes. The stunning, three-dimensional flowers come in all color combinations except for a true red and often are used for flower arrangements.
Bearded irises are just one of the many types of iris plants that are grown in the United States. What makes a bearded iris is the “beard” that appears on the three downward petals. The “beard” is the stamen part of the flower that produces the pollen. The other three petals, called the standards, curve upward. In the center are the pollen receptacles or the style arms. They can be as short as 4 inches to 40 inches tall and can bloom from early spring to mid-summer.
Some will re-bloom. These plants have rhizomes, an underground stem, that multiply each year and can be divided easily. In fact, the plants should be lifted and divided about every 5 years. There are thousands of cultivars with flowers in every color combination except a true red. Bearded irises are often grown for floral arrangements. Bearded irises are flowering perennials that are deer-resistant and drought-resistant once established. The beautiful flowers attract bees, butterflies, and hummingbirds but all parts of the plant are toxic to people, dogs, and cats.
Plant Attributes
Common Name: Bearded Iris
Botanical Name: Iris germanica
Family: Iridaceae
Plant Type: Herbaceous, Perennial
Mature Size: 4-40 in. tall, 6-24 in. wide
Sun Exposure: Full
Soil Type: Well-drained
Soil pH: Neutral to Acidic (5.0 to 7.0)
Bloom Time: Spring, Summer
Flower color: All except true red
Hardiness Zones: 3-9 (USDA)
Native Area: Europe
Toxicity: Toxic to people, toxic to cats, toxic to dogs
Bearded Iris Care
Bearded irises are herbaceous perennials, sold by rhizomes. The rhizomes are planted in July, August, or September. They must be planted in a well-drained area, with full sun, and good air circulation. If you have heavy soil or soil high in clay, add organic matter or compost to improve the drainage. Raised beds are another alternative. The ideal pH is 6.8 but they are not overly fussy about that if there is good drainage.
To plant the rhizomes, prepare the soil by making sure it is loose and weed free. Spread out the roots, bury the roots, and bury the rhizomes as shallow as possible. Deep enough for it to remain stable but shallow enough that the rhizome’s topside is exposed. In very hot areas, the rhizomes may be covered with an inch of soil. Do not mulch. Plant about 12 to 24 inches apart, depending on the ultimate size of the plant. Water thoroughly and water until established.
When the plant flowers, remove the spent flowers or the entire flowering stalk to encourage more blooms. In the fall, trim the foliage to about 6 inches. Remove any dead or diseased foliage, spent flowers, weeds, and any fallen leaves. In the following spring, fertilize with a superphosphate fertilizer or a 10-10-10 or a 5-10-10 fertilizer. Fertilize again one month after blooming.
Each year, the rhizomes multiply. In about 5 years, the original planting will be overcrowded which will decrease blooms and increase susceptibility to disease. The rhizomes should be lifted and divided. Because they must be spaced out again, not all are replanted, and there will be plenty of extras to give to friends.
Light
Bearded irises are full sun plants.
Soil
Irises must be grown in well-drained soil to prevent rhizome rot. If the soil is compacted or high in clay, amend with organic matter first. If not possible, consider growing in a raised bed.
Water
When planting, water enough to get the plant established. Do not water overhead or in the evening. Established plants are drought resistant.
Temperature and Humidity
For the most part, these are summer bloomers that prefer warmth but not necessarily high humidity. Although they can be grown in the south they may not do well in very deep south with humid summers and warm winters.
Fertilizer
Fertilize in early spring and one month after they bloom. Do not use a high nitrogen fertilizer. Use a superphosphate fertilizer (one in which the first and third number is a zero and the middle number is high) or a 10-10-10 or a 5-10-10 fertilizer.
Types of Bearded Iris
The American Iris Society (AIS) has divided the bearded iris into six groups, in order of earliest to latest bloom time and shortest to tallest sizes.
Miniature Dwarf Bearded (MDB)
These are 4 to 8 inches tall, earliest to bloom, and used in rock gardens or planted in drifts. The flowers are small, one to 2 inches across. They can bloom as early as March, depending on the zone.
Standard Dwarf Bearded (SDB)
These are 8 to 16 inches tall, the flowers are larger, and tend to bloom early in spring (April). They are best grown in clumps.
Intermediate Bearded (IB)
These are 16 to 27 ½ inches tall and bloom in April and May. They can be grown in clumps or along a garden border.
Border Bearded (BB):
These bloom in early summer, same time as Tall Bearded but the height is shorter, around 16 to 27 ½ inches tall.
Miniature Tall Bearded (MTB):
The stems are thinner, and the flower sizes are smaller than Border Bearded and Tall Bearded but bloom at the same time. They're often called table irises because they are good for cut arrangements. They grow from 16 to 27 ½ inches tall.
Tall Bearded (TB)
These are 27 ½ inches tall and taller and may need staking. They have a lot of branching and many buds. Typically, these are summer bloomers but the timing of the bloom varies with the cultivar so they can bloom from late spring to early summer.
Award-Winning Irises
Because there are thousands of cultivars, it may be best to choose from award-winning irises listed on the AIS website. Each year, the AIS gives awards to the different classification of irises, including the six types of bearded irises. In addition, they sponsor the tall bearded iris symposium, which is an annual popularity poll of tall bearded irises. AIS members and nonmembers may vote. The top irises are ranked, and the results are published on the website. The list provides the plant’s rank in the current year and previous year, cultivar name, votes received, hybridizer’s name, introduction year, bloom season, height, and a brief description of the flower color.
Pruning
It is the practice with bearded irises to cut the foliage back in the fall to prevent pests and diseases. As you are cleaning up the bed in the fall, cut the fans back to about 6 inches and do not compost but trash.
Propagating Bearded Iris
The best way to propagate is by division of the rhizome in the summer. However, the planting will have to be divided about every 5 years, so a good time to propagate is when you have to dig and divide to prevent overcrowding. Here’s how:
After the blooming period, dig around the perimeter of the planting with a gardeners fork to loosen the plantings. Be careful not to stab the rhizomes.
Using your hands, lift the plantings. If you are concerned that the foliage will stab you in the eyes, you can cut the foliage back to about 6 inches before you lift. Throw away the foliage, do not compost.
Brush off the soil, examine the rhizomes. Remove and trash any diseased, rotted, or old woody parts. Look for the iris borers and if you see them or damage caused by them, remove and trash. Separate the rhizomes so that each one has a fan of leaves. Save only the healthy rhizomes with foliage attached. If you had not already cut the foliage, do it now.
Replant but with the usual 12 inch spacing so will have more than enough to plant again, elsewhere in the garden, or share with friends.
Water thoroughly. Continue watering until established.
How to Grow Bearded Iris from Seed
It is possible to grow bearded iris from seed but it will take longer for the plant to mature enough to flower. You may not be able to purchase seeds commercially, but you can save the seeds from your plant. Remember that your plant is a cultivar so the plants you grow from seed may not have the same flower coloration. To obtain seed, instead of deadheading, leave the flowers on to develop the green seed pod. Let the pod and seeds mature and plant the following year in the garden, about ¼ inch deep. Water often so the seed germinates and does not dry out.
Potting and Repotting Bearded Iris
Bearded irises can be grown in containers outside, providing the containers are large enough. Most are hardy to USDA Zone 3 so they should be winter hardy in the south. However, they also produce new rhizomes every year which will get crowded in a container. Therefore, the container may only be large enough for a year or two. But the rhizomes can be lifted, divided, and replanted.
Overwintering
There are steps to take in the fall to prepare the bearded irises for winter. Remove any debris, fallen leaves from nearby trees, dead or diseased parts, and spent flowers. Cut the foliage to about 6 inches. This increases air circulation, sunlight, and dryness among the plants and removes fungal spores. This also removes borer eggs if present in the foliage. Put the leaves in the trash, not the compost. There is no need to mulch for the winter.
Common Pests & Plant Diseases
Pests
The most common pest is the iris borer (Macronoctua onusta) which is a moth larva. The female moth lays eggs in the summer on the foliage. The eggs sit on the foliage all winter long, and hatch in spring. In spring, the small green worms burrow into the foliage, feed inside, and work down to the rhizomes. By summer, they have grown into stubby grubs, “boring” into the rhizomes, eating the tissue, hollowing out the rhizomes and causing a soft rot.
If you see them in the spring on the foliage, try to remove that part of the foliage. When you are dividing the rhizomes, look for the borers as well as any damaged rhizomes. The best prevention is to remove and destroy previous years’ dead foliage in the spring but if you have a severe problem, you can use a systemic insecticide.
Another pest is the aphid that sucks the sap and can spread disease between plants. Aphids appear on the buds, blossoms, and foliage. They can be washed off with a hose or sprayed with an insecticidal soap.
Diseases
Spotted leaves can be caused by bacteria or fungus. Leaf spot will show up during mild wet weather but the difference between the two is that fungal spots are usually small oval spots that do not grow whereas bacteria spots are pale spots that grow larger and develop white centers. A fungal disease will persist well into the summer. The plants can be sprayed with a fungicide. There is no cure for a bacterial disease so the plants will have to be removed.
How to Get Bearded Iris to Bloom
Bearded irises make excellent cut flowers. Many are fragrant, ranging from sweet floral to spicy, musky, citrusy, and even very sweet, like root beer or grape soda.
Bearded irises bloom from the top down. Individual flowers only last a few days, and it is best to deadhead the spent blossoms, which will get wrinkled and mushy. Although you can snip individual flowers, this can become onerous. It may be easier to wait until all the flowers bloom on one stalk and cut the stalk down to the base. Deadheading encourages more blooms and removes the unsightly flowers.
All the six categories have cultivars that re-bloom, usually 4 to 8 weeks after the initial bloom. However, subsequent blooms are not as reliable. It is best to deadhead to encourage more blooming.
For maximum blooms, make sure the plant is in full sun and fertilized properly. Also, every few years, you will have to lift and divide the rhizomes as overcrowded plants will have diminished blooms.
Common Problems with Bearded Iris
Lack of Blooms
Lack of blooms can be caused by several factors: too much shade, overfeeding with fertilizer high in nitrogen, not feeding at all, rhizomes are planted too deep, over or under watering, or the irises have been growing in the area for many years and are overcrowded. If this occurs in the beginning of the planting it can be the sun, fertilizer, rhizomes planted too deep or a watering issue. If this occurs with an old planting, it could be that they have not been fertilized enough or that the rhizomes have to be divided.
Damaged Foliage
If there is damaged foliage and ragged edges, it may be caused by the iris borer larvae. This is a small caterpillar feeding into the foliage. Cut that part of the foliage off, trash, and keep an eye out for further damage.
Yellow Foliage That Collapses
This may be caused by the iris borer which is now feeding in the rhizomes and destroying the rhizomes. Lift the rhizomes and see if you can see the borers. If so, remove those rhizomes. Yellow foliage also can be caused by too much water in the soil. Either the soil is not draining well or there has been too much rain. In this case, try to plant in another area that is well drained, amend the soil, or try a raised bed.
For more Southern Living news, make sure to sign up for our newsletter!
Read the original article on Southern Living.
