Though iris flowers look elegant and delicate, they are sturdy and rugged plants. When they are in trouble, though, the first signal is usually the iris leaves turning Yellow. The issue may be improper watering, improper fertilization, lack of light, pests, or disease.
When friends ask for gardening advice, they often seem under the impression that iris flowers are incredibly difficult to grow. But, with the right amount of watering, light, and fertilization, they will thrive and bloom beautifully.
These tall flowers, named after a Greek goddess, are known for their beauty. They come in a huge range of colors and varieties, and are beautiful in pots, in the garden, or as cut flowers on display.
They are generally very easy to go and keep healthy. However, they have some specific requirements which, if not met, can severely impact the plant’s health and cause the leaves to turn yellow. Let’s look at the most common causes of yellowing leaves in irises.
Once established, irises don’t need a lot of watering, and overwatering can have detrimental effects on the plant’s rhizomes (the underground stems) leading to poor health and the iris leaves turning yellow.
Generally, in dry weather, the plant only needs watering every 7 to 10 days. Make sure that the topsoil is completely dry before watering the flower.
Ensuring that the soil is well-draining will also prevent the plant from becoming waterlogged.
If you have overwatered the plant, this may have resulted in root rot. This can also happen if the rhizome is accidentally nicked while pruning the plant, as it opens a pathway for bacteria.
Don’t worry, this is completely treatable. Carefully cut around the infected part of the rhizome and remove any mushy or damaged parts. Leave this part to recover in fresh soil.
Do not completely neglect to water your iris, however. Unless it's raining, your plant will still need its weekly watering. Without any water, the leaves will also yellow and the plant will wither.
Once on a good watering schedule, the leaves will recover and return to green.
While it is great to grow your flowers in rich soil, irises can suffer if overfertilized. Regular potting soil from a garden center can often be too nutrient-dense, and using this kind of soil is a common mistake made by new gardeners.
Just like overwatering, overfertilization causes root rot. As suggested above, cut away the infected parts of the plant and replant the iris to restore the iris to health.
Like other perennials, the iris prefers neutral soil. If your soil is too acidic or alkaline, this will begin to damage the plant and you will see warning signs such as yellowing leaves.
Use lime to fix acidic soil and sulfur to fix alkaline. Test the soil with a home soil test kit to see what pH your iris’s soil is. The ideal pH for iris flowers is 6.8, which is slightly acidic. Aim for within 0.5 of this number.
Add ground limestone to make acidic soil more alkaline. Agricultural sulfur (powdered sulfur, aluminum sulfate, or iron sulfate) will make alkaline soil more acidic.
If your soil was very alkaline or acidic, this was likely what was making your plant turn yellow. Adjusting the pH should soon restore the plant’s health.
Irises need a fair amount of light to thrive and bloom. Without a good 6 to 8 hours of sunlight in their growing period, they may wilt and die.
If your plant is quite shaded, this is the likely cause of the yellow leaves. Move the plant to a spot with more direct sunlight for better results.
Typically, irises are fairly pest-resistant. But, slugs, aphids, and scale insects can all infest the plant. Their feeding will sap the plant of its nutrients causing it to turn yellow.
Slugs can be prevented or eradicated by laying out slug traps or slug bait. For aphids, scale insects, or other small insects, treat them with neem oil. Spray a mixture of the oil mixed with water onto the plant after sunset. Without these insects’ feeding, the plant will return to health.
Frequently Asked Questions
With such a famous flower, there’s many more questions to answer. Here’s the answer to some common questions.
Q: How tall do irises grow?
A: Some irises can grow up to 4 feet tall. You may need to stalk the iris to prevent it from falling over.
Q: Are irises toxic?
A: Iris bulbs, leaves, and stems can potentially contain irisin, iridin, or irisine. These are mild toxins bit can cause stomach irritation if eaten and possibly cause skin irritation. Make sure to prevent pets from eating irises.
Q: What are irises used for?
A: As well as an ornamental plant, irises are used to make essential oils. The rhizomes are also used to produce orris root powder, which is used in perfumery and gin making.
Orris isn’t toxic but is the reason some people are allergic to gin.
Iris Leaves Turning Yellow – Conclusion
While iris flowers are sturdy, they respond poorly to too much fertilization or water. So less is more when it comes to this care. If neither of these appears to be the cause, check for signs of pests and test the pH level of the soil.
Through these measures, you can find out what is turning your iris’ leaves yellow and take action to get it back to its former beauty