Problem #1: Planting Your Bearded Iris Too Deep
This is one of the most common reasons that Bearded Iris do not grow or produce the big, fabulous blooms they're known for. Bearded Iris rhizomes should not be buried completely underground, but instead, they should remain exposed at the surface. The tops of the rhizomes should be visible and you should be sure to spread the roots out as you bury them below the soil.
Bearded Iris are propagated and planted as rhizomes, sideways-growing stems that shoot out laterally, just beneath the surface of the soil. Each new shoot begins to form new roots and shoots of its own. Plants use rhizomes for food storage. Ginger, turmeric, and Canna are all well-known rhizomes.
Learn more about planting Bearded Iris here.
The tops of the Bearded Iris rhizomes should be visible when planted. Planting rhizomes too deep can result in slow growth and less blooms.
Problem #2: Rhizome Rot In Bearded Iris
If you’re having heavy rains or if you've planted your Bearded Iris in an area that tends to hold standing water, you may experience bacterial rot in your tubers.
How Do You Spot Rhizome Rot in Bearded Irises?
Rhizome rot usually occurs in the early spring.
Check often to see if your leaves and fans are turning brown or yellow and falling over. That's a strong indication that you’ll need to remove the soil around the rhizome to do some further investigation.
To remediate rhizome rot:
- Remove the soil around the rhizome, making sure to keep the roots intact and still in the ground.
- Using a garden knife, cut out any soft, mushy parts of the rhizome that seem to have rotted. (Be sure to dispose of these rotted pieces in the trash or at your municipal compost center, but don't add them to your home compost pile if you want to prevent the spread of future disease.)
- If less than 50% of the plant seems clean and unaffected by rot, cover the rhizome back up with soil.
- If it seems as though most of the rhizome is rotted, dig up the entire plant and cut out the affected tissue. Rinse the remaining plant in a solution of 10% bleach/water and let dry for several days before you re-plant.
To avoid rhizome rot, be sure to plant your Bearded Iris in an area with good drainage. If you don’t have any beds with good drainage, consider building a raised bed or adding peat moss to your soil. Overcrowding can also cause rhizome rot so make sure to start your Bearded iris out with plenty of room to grow.
Bearded Iris need at least six hours of sunlight per day.
Problem #3: Not Enough Sun
This problem is fairly easy to remedy; Bearded Iris love sun, sun, sun! They need at least six hours of direct sunlight in most climates. Lots of sunshine also helps to prevent problem #2 (rhizome rot).
Problem #4: Pests & Diseases
Pests and diseases in Bearded Iris often vary by geographic location and gardening conditions. One general rule of disease prevention is to keep your garden clean from debris and weeds as much as possible. Having said that, pests and diseases can show up in even the most pristine gardens, so it is good to learn how to diagnose and treat these issues.
Bacterial Leaf Spot (Disease)
How To Identify: Bacterial Leaf Spot (or Bacterial Leaf Blight) shows up on the edges of the leaf tips as small, pale spots. They then grow larger and develop white centers. This disease usually shows up when there has been a particularly mild winter.
How to Prevent: Bacterial Leaf Spot can be tough to prevent. Keep a close eye on your Iris after a mild winter and work to identify the disease at its earliest onset, removing infected plants as soon as you notice them.
How To Treat: While there is no cure for this disease, there are measures that can help to control the spread of the bacterial leaf spot on Bearded irises.
Because the disease can be transmitted via garden tools and water, always be sure to wash your tools with a 10% bleach/water solution after dealing with infected plants. Remove any diseased plants and dispose of them in the trash or municipal compost center, but avoid adding them to your home compost.
Fungal Leaf Spot (Disease)
How To Identify: Fungal Leaf Spot appears somewhat similar to Bacterial Leaf Spot, but the small oval spots on the leaves do not grow in size. They do, however, form a distinct red/brown border. This disease is prevalent in wet, rainy weather so be sure to pay extra close attention during spells of rain-filled and high-humidity days.
How to Prevent: Always give plants plenty of room to grow and be sure to divide them as they begin to spread and naturalize.
How To Treat: If Fungal Leaf Spot appears, simply cut the tops off of the affected leaves. If the disease persists, you can use a natural fungicide, spraying in the fall and early spring, as a last resort.
Aphids, which are small green or gray insects, appear on the Iris leaves and suck out the leaf sap. Aphids can also spread disease between plants. (Credit Don Graham/Flickr)
How To Identify: Aphids, which are small green or gray insects, appear on the Iris leaves and suck out the leaf sap. Aphids can also spread disease between plants.
How to Prevent: There isn’t much you can do to prevent Aphids, but attracting beneficial insects (such as ladybugs) that eat these pests can be an effective solution. Marigolds are a great variety to add to the garden to help attract beneficial bugs. How To Treat: These little pests are large enough to pick off your leaves or crush between your fingers. Spraying a mixture of liquid dish detergent and water is also effective.
Iris Borer (Pest)
How To Identify: Common in the Eastern and Midwestern parts of the country, the Iris Borer can wreak havoc on your Bearded Iris. Iris Borer lays its eggs in the fall on old foliage and neighboring debris. The eggs survive the winter and hatch in the early spring, finding a home on new Iris foliage. They are often hard to identify but can be seen on the foliage, often leaving a slimy trail behind them.
How to Prevent: Keeping your garden clean and debris-free is the best way to prevent an Iris Borer infestation.
How To Treat: If you catch them before they’ve made a home in your rhizomes, simply squish them between your fingers (fun, right?)
Make a homemade soapy spray by mixing one tablespoon or less of dish soap (we recommend Seventh Generation’s Free & Clear) per one quart of water.