Geraniums are well known and one of the front garden’s most lovely bedding plants. That beautiful sight would seem less so if there were yellowing on its leaves.
With their drought-tolerant characteristic, bright-colored pompom-like flowers, they are actually of two genera (geranium and pelargonium), one which can handle much colder temperatures while the other species like it hotter.
Knowing this difference will often help diagnose health problems, like when the leaves turn yellow.
Causes And Treatment of Geranium Leaves Turning Yellow
Here are the different causes and treatments of Geranium leaves turning yellow:
One cause of yellow leaves on geraniums is over-watering. Geraniums like to be kept in moist but not wet or soggy soil. If you’re watering your geraniums every day or even every other day, that’s probably too much. Water your geraniums once a week, and ensure the pot has good drainage so the roots don’t sit in water.
If you are over-watering your geraniums, let the soil dry out completely before watering again. And if you see yellow leaves forming, cut back on the watering even more.
2. Too Little Water
One of the most common reasons for yellow leaves on geraniums is too little water. If you don’t water your plant regularly, the leaves will turn yellow and eventually drop off.
Your plant needs about an inch of water per week, so ensure you’re watering it deeply and regularly. If the soil you root the plant is dry, it’s time to water.
Another sign that your plant is thirsty is if the leaves are drooping. Drooping leaves are an indicator that you should water your plant immediately. Once the leaves start to turn yellow, it’s often too late, and they will not recover.
3. Plant Food Deficiency
One of the common causes of yellow leaves on geraniums is a deficiency in plant food. The deficiency happens when the roots of the plant cannot absorb enough nutrients from the soil, which then causes the leaves to turn yellow.
There are a few things that can lead to plant food deficiency in geranium:
- The soil might lack nutrients because it’s old or hasn’t been fertilized recently.
- The plant might get too much water, which can leach nutrients out of the soil.
- The plant might get too much sun, which can cause the leaves to lose their chlorophyll (the green pigment that helps plants absorb light).
If you think your geraniums might lack nutrients, the best thing to do is fertilize them with a high-quality fertilizer designed for plants.
4. Soil pH Imbalance
One of the more common causes of yellow leaves on geraniums is a soil pH imbalance. The ideal pH range for geraniums is between 6.0 and 7.5—any lower than that, and you will start to see problems.
If your soil is too acidic, you’ll notice that your geranium leaves start to turn yellow around the edges. This is because the plant cannot properly absorb nutrients from the soil and starves.
The same thing can happen if your soil is too alkaline. The solution in both cases is to adjust the pH of your soil, so it’s in the ideal range for geraniums. You can add sulfur to lower the pH or lime to raise it.
5. Too much sun
Geraniums love the sun—but too much of a good thing can cause the leaves to turn yellow. Excessive sunlight results in sunburn and makes the plant’s leaves hang and then dry out.
The long exposure to heat also causes the soil to absorb water, dehydrating the plant and inhibiting its growth. If this is the issue, move your plant to a shadier spot.
While pest infestations do not result in a huge change to yellow, these attacks can cause yellow, brown, or black spotting as the pest feeds on the leaf’s sap, dehydrating it. If this might be the issue, check your plant for signs of pests or disease and treat it accordingly.
7. Geranium Fungal Diseases
Geraniums are susceptible to fungal diseases, such as botrytis blight, pelargonium rust, and bacterial leaf spot. These diseases may cause the leaves of your plant to turn yellow or brown and affect the stems and flowers.
- Botrytis Blight
Also known as gray mold, Botrytis blight is a fungal disease affecting many plants, including geraniums. The signs and symptoms of botrytis blight are yellow leaves on the plant and brown or black spots. This fungus thrives and expands in moist environments and can spread quickly around a garden if left unchecked.
When controlling botrytis blight, carefully remove infected leaves from your plant and water. Another control measure is to avoid overcrowding plants; this will help to prevent the fungus from spreading.
Ensure you plant geraniums in well-drained soil and water them daily in the morning so the foliage can dry out before nightfall. This will also help prevent the fungus from taking hold. With standard vigilance, you will keep botrytis blight under control in your garden.
- Bacterial Leaf Spot
If your geranium leaves have turned yellow and you notice it is developing water-soaked lesions, it’s likely the plant has a bacterial leaf spot. Bacterial leaf spot is a type of bacteria that expands and grows in moist conditions triggering this disease.
It is good news, though, that bacterial leaf spot is quite easy to control. Begin by ensuring your geranium plant isn’t being overwatered. Also, ensure you water the plant at the base, thus avoiding wetting the foliage. Importantly, keep the leaves dry as much as possible.
Remove any infected leaves from the plant and sterilize your tools that came in contact with the bacteria. Another good idea is to space your plants to prevent overcrowding and increase air circulation.
- Pelargonium Rust
The most common sign of pelargonium rust is a yellowing leaf with brown spots on its surface. If you leave this fungal disease unaddressed, it can spread across and around to the rest of the plant resulting in leaf yellowing and the affected plants’ leaves falling.
Pelargonium rust is common in humid climates and can be spread by wind, water, or contact with infected plants. To prevent this disease, the best practice is to water early in the day, so the leaves have time to dry before it gets dark.
In addition, it is vital to trim off any dead or dying leaves from the plant, reducing the risk of infection.