Geraniums are supposed to be easy to grow. And they can be. If you don’t give them a reason to throw a hissy-fit.
One of the first signs that there’s trouble in your geranium is leaf discoloration, and it looks dramatic.
Before you start yelling at your Echo, “Alexa: Why are my geranium leaves turning yellow?” take a breather, get calm, then carry on reading below.
Let us unearth the multitude of reasons that contribute to geraniums behaving weirdly.
Why are my geranium leaves turning yellow?
Too much water causes yellow leaves on the lower part of geraniums. Drought results in yellow leaf edges. Fungal infections trigger yellow spots on leaves, and pelargonium rust causes leaf discoloration too. Nutrient deficiencies are often the culprit for yellow leaves on geraniums.
Discover the Likely Cause of Your Geranium’s Leaves Yellowing
Pelargonium rust is specific to the zonal geranium or pelargonium.
This is a fungal disease that causes yellow spots to appear on upper leaves that have white (ish) blisters on the leaf’s underside.
The yellow rings eventually develop brown spots (rusting) causing all the leaves to wilt, yellow then eventually drop.
Pelargonium rust can affect houseplants and garden shrubs.
It affects only the zonal variety and is most present on new plants. The fungus can be dormant for two weeks before symptoms show.
In most cases, this develops when the plants have little air circulation and are kept in high humidity.
Consistently wet leaves will also contribute to pelargonium rust so be careful never to overwater these.
The best practice is to water the soil and let the roots nourish the leaves.
Growing geraniums with the wrong soil type or improper fertilizers can cause the leaves on geraniums to discolor.
- A lack of zinc causes leaves to yellow first, eventually turning purple.
- A lack of nitrogen results in the lower leaves turning yellow with brown tips and they’ll have stunted growth. Eventually, the brown tips will spread across the leaf, killing it.
- A lack of phosphorus causes brown tips that’ll eventually lead to brown leaves on geraniums
- Magnesium deficiency shows on older leaves as yellowing along the leaf edges and between the leaf veins. Epsom salts can fix that.
Yellow leaves on geraniums are often just a signal to give it some plant food.
Take clues from the type of discoloration to know what you need to feed it.
- Stunted growth gets fixed with nitrogen
- Zinc fixes yellowing leaves
- Nitrogen encourages growth preventing all the bottom leaves from yellowing
- An uptick of phosphorus fixes brown tips on leaves.
Geraniums are heavy feeders requiring a liquid fertilizer as frequently as every two to three weeks during bloom season.
To ensure they get enough of the macronutrients they need, use a balanced fertilizer such as 10-10-10 or 20-20-20.
Geraniums love the sun. They hate water. Only give them enough to survive. Not enough to bathe in.
Overwatering a geranium will always result in all the lower leaves yellowing.
Avoid watering the plant when the soil’s still moist. These are drought tolerant and favor watering when the soil’s dry to your touch.
Finger test the soil first and only water when you find that the top inch’s dry.
Or, when only the leaf edges are yellow, you’ll have to continue reading below to know what’s causing this problem.
If you’re never quite sure if your geranium’s thirsty or ill, look at where the yellowing parts on the leaves are.
As mentioned above, yellow leaves only on the bottom of the plant is a sign it has too much water.
When there are not enough fluids for it, the leaf edges yellow first.
If you can’t quite nail the finger test method, the next safest option is to deliberately subject it to drought. Crazy, eh?
These are drought tolerant. Leaf edges yellowing is the first sign of water stress indicating it needs a drink.
When it does, make sure to water only the soil, not the foliage itself.
Geraniums are prone to a number of fungal infections. Nearly every one of them can be contributed to wet leaves.
Powdery mildew, botrytis blight, bacterial blight, and perhaps the worst, Alternaria and Cercospora leaf spots, which are brown spots with yellow halos. These will trigger defoliation.
The safest prevention method for any fungal infection is to water at soil level and never use a watering can or spray hose to water the plant from above. Two other factors to keep in mind are humidity levels and air circulation.
The risk of fungal or bacterial infections is reduced when geraniums have good air circulation and kept at moderate humidity levels.
Deadheading is an important aspect of geranium care because a lot of infections start on the spent blooms. Pinch those blossoms off before they start falling to the ground.
For outdoor geraniums, overwatering can easily happen after a heavy spring shower.
If the leaves are overly wet for an extended period, look out for fuzzy fungus emerging, which is most likely powdery mildew.
One of the most severe fungal infections for geraniums is verticillium wilt. It causes the bottom half of the plant to wilt, leaves to turn yellow, stunted growth, and eventual leaf drop.
Verticillium wilt is a soil infection that’ll remain there indefinitely.
In garden soil, the top six inches can be treated with soil solarization to kill the fungus.
In potted plants, it’s easier to repot in fresh potting mix.
Read more about how to grow geraniums here.
Frequently Asked Questions Related to Yellowing Leaves on Geraniums
Should yellow leaves be cut off geranium plants?
Every leaf on a plant serves an important role in photosynthesis. They need to be green though. However, you need to remove the yellow leaves as they don’t produce any energy for the plant. It’s a wasted resource. It’s better to remove yellow leaves to make way for new green foliage to emerge that will provide the plant with the energy resources it needs.
Are yellow leaves common on geraniums indoors?
It’s surprising, but it’s common to see yellow leaves when you grow them indoors. However, it’s more common to see them with those grown outdoors than the ones overwintered indoors. The lower light levels, drier air humidity, and stable temperatures will come as a surprise to an outdoor-grown geranium. Expect a lot of yellowing leaves when you first bring them indoors. Once it gets used to the different conditions, and less watering, it’ll regain its greenery fairly quickly.
Marcel runs the place around here. He has a deep passion for houseplants & gardening and is constantly on the lookout for yet another special plant to add to his arsenal of houseplants, succulents & cacti.
Marcel is also the founder of Iseli International Commerce, a sole proprietorship company that publishes a variety of websites and online magazines.