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Geranium Problems, Pests, and Diseases (Australian Guide)

Common geranium problems include yellow leaves, leaf rust, and holes in the leaves caused by pests.

Geraniums are one of the hardiest plants you can ever grow. If you’re lucky and your geraniums are growing in ideal conditions, you’ll most likely not experience any problems.

I have an old variety growing in my front garden along the fence. It’s often shaded during the day but is still healthy and produces lots of lovely red flowers without too much attention.

I’ve taken bits of branches that I’ve accidentally broken while pruning and stuck them in the ground elsewhere in the garden. These have grown into new plants and are thriving.

However, there are a few problems that you might experience with your geraniums. Here’s how to identify them and how to treat them.

Yellow leaves on geraniums



If your geraniums are exhibiting yellow leaves, it means that they’re getting too much water.

Remember that these are originally Meditteranean plants and prefer a hot and dry climate.

Therefore, if your plants have yellow leaves, allow them to dry out and trim off any unhealthy leaves or branches.

Make sure your plants are getting lots of sun and adequate airflow.

Rust on geraniums



Rust is a fungal disease that exhibits as yellow or orange spots or raised pustules on the leaves.

This can be prevented by ensuring that your plants are growing in a nice sunny spot and there’s plenty of airflow. 

To treat rust on geraniums naturally, there’s a registered organic fungicide called ‘OCP eco-fungicide’. This can be sprayed on your plants and creates a protective coating in the leaves to stop fungal spores from germinating.

This fungicide does not harm beneficial insects and is even safe to use on fruits and vegetables. 

Another thing you want to do is remove any of the infected leaves and throw them in the bin. This will help to prevent the spread of the disease.

If you do have this fungal problem in your garden, make sure that you only water the soil at the base of the plant and avoid getting the leaves wet as moisture and humidity encourage fungal spores to grow.

Holes in geranium leaves

Geranium Problems | Plant care

If you notice holes in your geranium leaves, these are probably caused by caterpillars.

The best natural control for this problem is to spot the caterpillars and remove them by hand.

Make sure you wear gloves and drop the offending caterpillars into a bucket of hot water to kill them.

If you don’t want to kill the caterpillars, just move them to another spot in the garden away from your geraniums. 

Other geranium problems

Other problems that you might experience with your geraniums are a lack of flowers, tall lanky stems, dieback and bacterial leaf spot.

Here’s what to do in each case.

Lack of flowers

If your geraniums are not flowering, it means that they’re hungry. Feed your plants with a controlled-release fertiliser such as Dynamic Lifter once a year in spring.

Alternatively, you can give them a liquid feed with Seasol Powerfeed or Charlie Carp once a fortnight during the warmer months.

Tall lanky growth

If your plants have tall lanky stems, it means that they need a prune. Just cut back all the stems by about one-third.

Geraniums do benefit from regular pruning to maintain a nice shape.

Dieback

It’s quite common for older branches on geraniums to dieback. This can also happen if your plants have been exposed to frost.

I just cut back the branches to nice healthy green growth when this happens to my geraniums.

Bacterial leaf spot

This shows up as brown, sunken spots on the leaves. Being a bacterial infection, it can be difficult to treat.

It’s more common if you live in an area that has warm, humid summers.

Your best course of action is to cut off the diseased foliage and put it in the bin.

If the disease has spread too far, find some stems that are still healthy and use these to propagate new healthy plants to replace the diseased ones.

‌FAQ

What do overwatered geraniums look like?

If your geranium is overwatered, it will have yellow leaves and drooping blossoms that look wilted. To fix the problem, let the soil dry out and only water when the top 10 cm of soil is dry.

Should geraniums be watered every day?

Geraniums are Meditteranean plants and like hot and dry conditions. Therefore, they don’t have to be watered every day. Geraniums that are growing in the garden should generally not need supplementary watering.

Can a yellow leaf turn green again?

No, once a geranium leaf has turned yellow, it’s best to cut it off as it will not turn green again.

Photo of author

Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.

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1 thought on “Geranium Problems, Pests, and Diseases (Australian Guide)”

  1. My geraniums have bloomed for 2 yrs straight on a glassed-in veranda. Have huge long, thick stems (ugly) but tiny leaves. I may be overwatering them during summer. may need repotting? Any advice most welcome.

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