Even though Rose of Sharon is a hardy hibiscus that usually thrives with little or no care, it can suffer common plant maladies such as yellowing leaves. This problem has many causes and may be serious or a mere trifle.
In this article, we review why Rose of Sharon may have yellow leaves and provide smart fixes to help you deal with this problem. Read on to learn more.
Should You Always Be Worried About Yellow Leaves On Rose of Sharon?
An occasional yellow leaf is nothing to worry about. Each leaf has a life span; when it is over, it will turn yellow, die and drop off.
You needn’t be concerned as long as your Hibiscus plant is not losing massive numbers of leaves and appears otherwise healthy. Just pluck off the occasional yellow leaf and go your merry way.
Lots Of Yellow Leaves Mean Trouble
Root rot is a universal cause of yellow leaves in many plants. If your deciduous shrub stands in dense, soggy soil, the roots cannot breathe, and fungal infection can occur.
The solution is to cut back on watering and ensure your flowering shrub is planted in light, airy, moist, well-drained soil. If your Rose of Sharon is in a container, be sure it has ample drainage holes and that the holes are not blocked.
Here are the steps to take to prevent root rot.
Watering too frequently or too much will also cause root rot. So it’s best to avoid waterlogged soil.
Instead, practice soak and dry watering, allowing the top 2″ or 3″ inches of soil to dry before providing a thorough watering.
Other fungal diseases that can cause the yellowing of leaves of Rose of Sharon include leaf spots, blights, and cankers.
Infestation by pests such as whiteflies and aphids may also cause the yellowing of leaves. For the most part, the Rose of Sharon is not subject to pest infestation; however, a plant weakened by overwatering may easily fall prey to pests.
These insect pests can also cause flower buds to fall off before opening.
If you find unwelcome insects on your Rose of Sharon, blast them off with a strong spray of water from your garden hose, and follow up with a treatment of horticultural oil, neem oil, or insecticidal soap. A weekly preventative treatment can help keep pests off your plant.
You can address these pests, especially aphids, by spraying soapy water on both sides of the leaves at dusk or dawn.
Applying an all-purpose fungicide to the entire plant will also work well.
Too little sunlight can also cause your Rose of Sharon to have yellow leaves. These deciduous plants need at least four hours a day of direct sunlight.
You may also protect your woody shrub against intense sun exposure by providing an afternoon shade instead. Partial shade will also work well.
If your plant is in a container, monitor and change its location to be sure it is getting the right amount of sunlight.
Aside from preventing yellow leaves, you can also promote more flowers by giving ample sunlight.
If planted in the landscape, keep an eye on surrounding trees. If they overgrow your Rose of Sharon and block the sun, prune them back to let the sun in.
Too much watering
Overwatering can also be a reason your Rose of Sharon leaves is turning yellow and cause brown spots to appear.
This is usually caused by excess moisture around the plant’s root ball. So it’s best always check the soil moisture and provide excellent drainage to prevent this.
Once established, you need not worry about watering because the rose of Sharon becomes drought tolerant.
Chlorosis! How to Treat Yellowing Foliage
Inadequate nutrition may cause chlorosis on your Rose of Sharon. This yellowing of entire leaves is caused by a lack of nitrogen, potassium, magnesium, iron, zinc, or manganese.
Rose of Sharon also doesn’t typically need a lot of fertilizer, and excessive fertilizing will cause its own problems, such as burned roots.
Just provide adequate hibiscus plant food for healthy foliage and beautiful flowers.
To avoid chlorosis, test the pH balance of your soil. You may need to amend it with ammonium sulfate or sulfur if it is very alkaline. High alkalinity can interfere with a plant’s ability to absorb the nutrients it needs.
You should also test the nutrient levels in your soil. This will not only help you pinpoint exactly what you need to add, but it may also reveal nutrient excesses that may be causing harm.
For example, very high levels of calcium, copper, phosphorus, zinc, or manganese in the soil can interfere with your plants’ ability to absorb iron.
To avoid problems with chlorosis in the future, remove weeds and turf from around the base of your tropical hibiscus.
Add a two-inch thick mulch of cedar, pine, or hardwood chips. This will help keep moisture in the soil and will passively reduce alkalinity in the soil as the mulch breaks down.
Take care not to allow the mulch to touch the trunk of your Rose of Sharon bush because the decomposition process may burn the plant.
Mulch decomposition may also provide all the nutrients your plant needs; however, if you want to fertilize, keep it light.
Apply a half dose of a balanced fertilizer (10-10-10) on your Shrub Althea early in the springtime and again mid-summer. Water thoroughly before applying the fertilizer, then water it thoroughly afterward.
Will Yellow Leaves Recover?
When a leaf of your Rose of Sharon begins to turn yellow, it is a harbinger of death for that particular leaf. It won’t recover, so you may as well go ahead and prune yellow leaves away.
They drain the plant of energy and provide shelter for plant pests and encourage the growth of fungi, viruses, and bacteria. Prune yellow leaves close to the stem using a very sharp, sterilized cutting implement.
Moreover, just ensure to thoroughly clean your pruning tools like pruning shears to prevent any spread of disease.