One day you have your plants looking beautiful, healthy and radiant and the next you start to notice strange things about them. Your plant is a living being, in constant growth and development and although it has no voice, it has other ways of communicating its needs and vicissitudes: the leaves. By observing the colouring, size and development of your plant's leaves, you will know what is happening to it.

If the leaves of your plant are black, you should know that there are several causes of this problem and the solution depends on them. Don't worry, you will learn how to diagnose and cure black leaves on plants.

what causes black spots on leaves?

In short, there are 2 causes of black spots on leaves: environmental and infectious. Among the environmental causes we can mention warm weather. Warm air causes the moisture in the leaves to evaporate very quickly, so they will dry out. This is common in tropical plants, which are not used to direct sunlight. This is easy to diagnose, because the leaves look dark and dry, crumbling to the touch.

Excess fertiliser when temperatures are high can also burn the leaves, causing black lesions. This happens because heat causes plants to do the nutrient uptake process at an accelerated rate, so it will take up more fertiliser than it can handle and affect the leaves.

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Fungal and bacterial infections are common causes of black spots on leaves. These are easy to spot because instead of starting at the tip of the leaves, they come up randomly on the surface. There is another type of fungus that looks like a black powder that settles on the leaves. It is important to detect what the lesions look like in order to treat them properly.

• Black spot fungus

The name of this disease is diplocaron rosae, and it affects any type of plant with healthy leaves. The conditions in which this fungus thrives occur when the plants are watered, the water falls on the leaves and stems and stays wet for 6 to 9 hours. It starts with small black spots on the leaves, which increase in diameter and develop a yellowish border that covers the entire leaf, killing it. To kill this fungus you need to spray the plant with a good fungicide. Neem oil is perfect for this and is natural. Some people have tried potassium soap with success.

• Fumigilla or Fumagina

This is a moisture-loving fungus, but often appears as a companion to plant parasites such as aphids, scale insects or whiteflies. These tiny insects produce a honeydew that attracts blackleg. The good news is that this condition will not kill your plant, but it will cause aesthetic problems and may hinder photosynthesis a little.

The solution starts by attacking the parasite that attracted the blackleg. Then you need to remove the powdery mildew from the leaves. If the infected plant is not very large, you can do this manually with a damp cloth or by using a pressurised water jet. You can use potassium soap, which will help you get rid of insects and treat the fungus. If necessary, carry out a sanitation pruning.

Remember that the best remedy is prevention. Avoid watering your plants at night (especially if they are succulents), try not to get the foliage wet and if you see that one of your plants is sick, isolate it from the rest of the plants. Cut off the diseased leaves and start treating it immediately. It will surely recover its beauty and vigour.