Why Does My Lobelia Die? 7 Reasons

There are different types of Lobelia plants, and these are lovely plants that will make a great addition to gardens of any size. There is a couple of problems that can affect these plants and cause the plants to turn brown and show signs of dying.

The common reason why Lobelia might be dying are: 

  • Too much or not enough water
  • Too much sun/heat
  • Fungal problems
  • Pests
  • Unsuitable hardiness range
  • Brown plant tissue
  • Dried out leaves

Lobelia plants are a perennial type of plant; however, they are often considered to be annual as they are not able to withstand extreme conditions.

Reasons why Lobelia might be dying

Too much or not enough water

Incorrect watering can be a cause of problems for many plants, and this can be either too much water or not enough water. Overwatering can cause a lot of problems for Lobelia, such as root damage and even death. When a plant has been overwatered, it will develop mold around the base of the stem, on the soil surface, and on the leaves. 

Dead roots on a plant reduce the amount of nutrients and fluid that the plant can get into the plant tissue. Lobelia plants are more likely to be affected by too much water.

One way to avoid problems caused by incorrect watering is to ensure that you only water the plant when the soil feels dry to touch. Ensure that the root balls of the plant are well watered when they are first planted.

Too Much Sun/Heat

The tissue on the Lobelia plants is not designed to function under extreme heat. Therefore extreme conditions can cause the leaves to curl up and turn a brown color. When the temperature is too hot, the outer edge of the leaves may curl up in an inward direction. These problems cause the plant to turn brown due to the stems being unhealthy. 

The best way to deal with this problem in your Lobelia plants is to move the plants to an area that is shaded and increase the level of watering. If the plants are moved in time, they will develop new healthy leaves, and the plant will get back to being healthy. 

Fungal Problems

Fungal problems can be a reason why a plant will turn brown and show signs of dying, especially when the fungus feeds directly from the cells or from the inside of the plant. The parasitic fungus that is external can be easy to detect. However, the internal parasitic fungus can be harder to detect. A common external fungus that affects these plants is rust. Rust is a fungal condition that starts on the tissue of the leaves and will quickly cover them in spores that are brown, orange, or dark-colored. 

When your Lobelia plants are affected by rust, it is a good idea to remove a few of the affected leaves or if the problem is widespread, then use some neem oil spray to treat the problem. It is possible to reverse the problems caused by rust fungus if it is dealt with quickly. To avoid this fungal problem or to prevent it from happening again, give the plants more room to breathe as they need to have a good circulation of air. 


There are not many pests that will affect Lobelia plants. However, one of the things that will affect them is mites, and these are some of the worst problems for plants. Mites will feed on the leaves of the plants, and they will suck the juice from individual cells, which results in the cells dying and brown spots appearing on the leaves. 

As the colonies spread on the plant, the leaves would develop an overall bronze color. The best way to treat the problems of mites is to spray the mites using neem oil or use an insecticide soap on a weekly basis until there are no signs of mites or damage on the plant. 

Another pest that can affect Lobelia plants is corn earworm. This pest will affect the plant from the base upwards. The corn earworms will make a hole in the stem of the plant and feed on the inside of the plant, which will eventually make the stem hollow. As these pests feed, they damage the transport of tissue, causing the stems and leaves to slowly turn brown and eventually collapse. 

These pests may spread from one stem to another, causing further damage. When you suspect that your plants have been affected by corn earworms, cut out the affected areas, as it is unfortunately not possible to treat the larvae once they are inside the stem, but you could use a preventative spray of acephate around the base of the healthy stalks to prevent them becoming affected. 

Unsuitable Hardiness Range

Some of the species of Lobelia plants are described as being annual as they are unable to cope with the harsh winter in some areas. These can survival all year round in warmer areas when certain requirements are met. There is no way that you can combat this problem except to be aware of how your local climate could affect the plant. 

Although these plants can be kept outdoors, they are unable to survive extreme conditions, and even when moved inside, there is no guarantee that these plants will be able to survive. It is a good idea to trim these plants back during the cooler months when they start to struggle and place a cover over them, as this can prevent the plant from permanently dying.

Brown Plant Tissue

Brown plant tissue can be a problem that can cause a plant to die. When plant tissues have turned brown, regardless of whether it is a small or big leave, it can result in the death of the plant. Damaged tissues will mean that the cells are no longer able to receive nutrients through tissue transport, and this results in the plant wilting and collapsing. There are many problems that can affect the transportation mechanism of a plant, but most commonly, it is due to incorrect watering. 

When you notice plant tissue turning brown, then check the plant for excess water or overly dry soil and for any signs of pests or fungus. If you notice the cause of the problem, then you will have a better idea what you need to do to try and save the plant. 

Dried Out Leaves

During warmer weather, the leaves of Lobelia plants can become dried out, and in situations where dehydration is severe, the plant may become brown and die. Avoid this problem by regularly watering the plants so that the soil remains moist. If the plants do become too dry, water them and move them to an area that is cooler and shaded, then wait and see if you can reverse the damage. Take care to water the plant consistently as this will help it to retain moisture and prevent drawing it from the sides. 

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