Why Are My Lobelia Plants Turning Brown?

Does the browning of the leaves show in specs or spots?

Are there any small sucking insects on the leaves?

Does the browning starts from the base upward, a small hole in the base of lobelia stem is apparent?

Do you let your lobelia sit in soggy, flooded soil?

Do you water your lobelias rarely?

Lobelia is susceptible to few sucking insects. Mites are the most notable pests that such juices from leaves and leave specs of dead, brown tissue in them. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap, or pyrethrin as a last resort.

Rust is a common fungal disease that attacks lobelia. This disease usually starts on leaf tissues, quickly covering them in orange, brown, or dark-colored spores. Remove and destroy leaves infected with this fungal disease. As a last resort, spray or dust with sulfur, repeating as needed.

A corn earworm larvae bore a hole in the base of lobelia stems and feed inside, eventually hollowing the stem completely. As they feed, severing transport tissues, the leaves and stem slowly brown and collapse. Once larvae are inside it’s hard to treat them, but preventative sprays of acephate around the base of unharmed stalks can prevent infestation.

Overwatering or waterlogged soils cause plants to suffer from root rot that decreases the fluid and nutrients uptake. This may result in dying, browning plant tissue. Keep the soil moist, but do not allow it to become flooded.

Lobelia is a plant that needs consistently moist soil. If you do not water it regularly its tissue will start wilting and turning brown. Keep the soil moist at all times but make sure not to overwater to avoid root rot.

Lobelia with brown leaves but healthy stems may have been exposed to too much sun. These plants grow best in part shade and do not like direct sunlight that can scorch their foliage.