8 Coleus Diseases & Problems You Must Know (Signs, Treatment & Prevention)

According to many houseplant owners and gardeners, coleus plants are one of the easiest to grow and care for. 

But, that doesn’t mean it is immune to diseases and problems.

Just like any other plant, they can also become victims of nasty bacterial and fungal infections. And, as a responsible owner, you must find the cause and treat it immediately to save your coleus from further damage.

In this article, we will be explaining all the commonly seen coleus diseases and problems along with their signs, treatment options, and possible prevention tactics.

Coleus Problems

When it comes to commercially produced coleus plants, they are quite adaptable. But still, some conditions like pest infestations, nutrient deficiencies, light problems, abrupt changes in temperature and humidity, and soggy soil are too harsh for the plant to survive.

As a responsible coleus owner, it is your responsibility to find the symptoms of these problems and fix them before they worsen.

Let’s have a deeper look into all these coleus problems with their symptoms and possible fixes.

1. Watering Issues

Watering your coleus plant is a skill that you need to master if you want them to thrive.

Based on our analysis in different gardening forums, one of the very commonly seen problems is either overwatering or underwatering. Generally, beginner and intermediate gardeners tend to overwater their plants, while intermediate and experienced gardeners tend to underwater.

Signs of underwatering: yellow leaves, brown leaves, droopy leaves, rotten smell from the pot, always wet & damp soil, slow and stunted growth.

Signs of overwatering: discoloration in leaves, always wet soil, stunted growth, dry and dead leaf tips.

Solution: Set up a flexible watering schedule after considering the external climate and environmental conditions.

2. Light Issues

The next common problem seen in coleus plants is improper lighting.

It is also not surprising given that many seasoned gardeners admitted that they occasionally fall short of giving indoor plants the ideal amount of light.

Light issues include both too much light and too little light.

Signs of too much light: sunburn, leaves curling downwards, leaves turning yellow and brown, soil dries too fast, etc.

Signs of too little light: leggy growth, plant leaning towards the light source, leaves curling upwards, too much moisture in the soil, etc.

Solution: Different coleus plants have different light requirements. So, it is advised to check the light requirements of the coleus variety that you own. Check out our exclusive library to read growing guides of different varieties.

3. Temperature & Humidity Stress

Just like how water and light are important to coleus growth, temperature and humidity play a key role.

And, it is also the least talked about care parameter when it comes to indoor gardening.

The majority of the coleus variety thrives in the medium temperature range (70 to 75^oF) with a humidity of over 50%. Also, keep in mind that these plants are very sensitive to sudden temperature changes.

Signs of temperature & humidity issues: Dry leaves, very low or high moisture in the soil, stunted growth, fading of leaves variegation, leaf burn, etc.

Solution: Fixing temperature and humidity issues depends on the location of your plant. If it’s indoor, then adding a heater, cooler, humidifier, or dehumidifier depending on the problem is enough.

However, for outdoor grown coleus it is very hard to maintain the temperature and humidity manually. The maximum that you can do is move the plant away from hot sunrays or cold waves.

4. Random Holes In leaves

Coleus plants have very soft leaves which makes them an easy treat for pests including leaf mining bugs and insects.

Depending on the location of your coleus plant, different pests can damage the leaves.

For indoor-grown plants, pests like mealybugs, spider mites, beetles, aphids, etc are responsible. However, cutworms, slugs, snails, etc will damage your outdoor coleus.

Signs of pest attacks: random holes in leaves, brown leaf spots, dry edges, flakes in stems, etc.

Solution: If you can spot bugs and pests in your coleus leaves and soil, clean the leaves with pesticides to repel them in the future. Also, it is recommended to isolate the plant right after spotting pests.

For a detailed discussion, check out our dedicated article on “Why are there holes in coleus leaves?”.

Coleus Diseases

Most of the commonly seen coleus diseases are either caused by bacteria or fungi. These diseases include bacterial leaf spot, root rot, stem blight, root knot, and downy mildew. Most of these diseases can be treated with fungicides if the infection is in the beginner stage. However, root-knot and root rot are considered to be major diseases that are quite hard to treat.

Let’s discuss each of these diseases in more detail so that you can identify and treat them easily.

1. Leaf spot disease

If you are growing indoor plants for quite some time, you might have already experienced leaf spot disease in not only coleus but other many houseplants.

Leaf spot disease in coleus plants is caused by either bacterial, fungal, or pest infestations. In the case of coleus plants, a dematiaceous fungus called Corynespora cassiicola is consistently found to be making the damage.

Additionally, another fungus Botryodiplodia theobromae is also reported to cause leaf spots in the coleus plant by many biologists.

Signs of leaf spot disease: yellow, black, and brown spots with holes all over the leaf.

Treatment: There is no way to cure already damaged leaves. So, it is advised to remove the leaves with sterilized pruning shears. To prevent the disease from happening in the future, clean the leaves and stem with neem oil or mild chemical fungicides occasionally.

2. Root Rot/Wilt

Among all the diseases that we discuss in this section, root rot disease is one of the most commonly seen problems despite being fatal to the plant.

Even though root rot in the coleus plant can be caused by many reasons including overwatering, poor drainage in soil, fungal infections, and overfertilization, in the majority of the cases it happens due to either overwatering or fungal infection.

Bot of those causes is correlated. Overwatered soil is a breeding ground for bacteria, fungi, and similar pathogens.

Based on various studies, different bacterias and fungi are identified to cause root rot in coleus plants. These include Fusarium chlamydosporum, Fusarium solani, Ralstonia solanacearum, black sclerotia, and Macrophomina phaseolina.

Signs of root rot in coleus: decaying smell from the base of the plant, slow or stunted growth, color change or fading in leaves, damp soil, blackening of the stem, etc.

Treatment options: Repotting the coleus plant in fresh soil after removing the rotten roots is the only proven technique to save coleus from root rot.

3. Stem Blight & Wilt

Blight disease is caused by a fungus called Rhizoctonia solani. Mainly outdoor coleus plants are infected with this disease. 

This disease can affect both the stem and leaves of your coleus plant. When there is significant humidity or during the monsoon season, blight disease is prevalent.

Signs of stem blight disease: Water-soaked leaf patches that grew quickly in size before turning light tan to brown and eventually dead are the commonly seen symptoms of blight disease. 

Plants that are severely infected will lose their leaves and die in a few weeks.

Treatment methods: Fungiciddes after repotting the plant in fresh soil.

4. Root Knot

Root knot is a disease caused by eelworms, which are minute, parasitic, soil-dwelling nematodes from the genus Meloidogyne.

According to a research paper published in the Central Institute Of Medicinal And Aromatic Plants Journal, these worms stimulate the adjacent root cells to divide and grow by burrowing into the soft tissues of young roots and root tips.

As a result, the coleus plants affected by this disease will have swollen roots.

Signs of root-knot disease: In the early stages, slow or stunted growth, and yellow and droopy leaves are the commonly seen symptoms. However, severely infected plants will unexpectedly wilt and die. Also, swollen roots are a sign of severe root-knot disease.

Treatment methods: Unfortunately, root-knot disease in coleus plants is not easily treatable in home conditions. If the infection is low, you can try to report the coleus plant in completely fresh soil and pot after removing the infected roots. There is a small chance your plant will recover, hence this is not a guaranteed treatment option.

For severe infection, there is nothing you can do other than throw away the plant and its soil.

Coleus Diseases & Problems – Frequently Asked Question(FAQs)

When you see problems or signs of disease in your coleus plant for the first time, it is natural to have many questions and doubts. To clarify your confusion, here we will answer some of the most frequently asked questions related to coleus diseases and problems.

Wrapping Up

Seeing your coleus plant with a disease is depressing. But, if you can figure out what is wrong in the earlier stages, it becomes very easy to treat.

If you see a couple of signs, don’t get depressed. Instead, compare the symptoms you are seeing with the signs of all the diseases that we described above. 

Once you find what is the cause, follow the treatment method recommended in the article and save your plant on priority. If saving is not an option, follow the preventive measures to at least prevent them from happening in the future.

Sources

To back up the information we provide in our articles, the Plantials team only uses high-quality sources published in peer-reviewed university or scientific research journals.

1. Medicinal Plant Coleus Forskohlii Briq: Disease And Management, Central Institute Of Medicinal And Aromatic Plants Via Academia.Net.
2. Fungal Diseases In Medicinal Coleus Plant, Tamil Nadu Agricultural University, Indian Journals.
3. Biological Control Of Root Rot In Coleus, World Journal Of Microbiology And Biotechnology.
4. Downey Mildew Of Coleus, University of Massachusetts Amherst.
5. Studies of a Phytophthora Species Root and Stem Rot of Coleus, University Of California.
6. Fertilizer Source and Irrigation Depth Affect Nutrient Leaching During Coleus Container Production, Journal Of Environmental Horticulture.