Senecio Is Dying
There are many reasons why senecio plants fail to thrive and show signs of stress. Typically the cause is too much of something. Senecio is a very low-maintenance plant that requires a small amount of watering, humidity, and fertilizing, along with quick drainage to keep excess water from rotting the shallow root system.
The most common signs of stress are seen in senecio’s modified leaves. They will either swell and split, indicating too much moisture, or shrivel up and appear to have a scar running down the length of the leaf, indicating dehydration. Leaf drop indicates the plant is too cold, and should be moved away from drafty windows, air conditioning vents, or outside doors. Leaves that turn yellow, brown, or black indicate too much fertilizer or sun exposure. While these issues are not desirable, they are relatively easy to fix when diagnosed early.
Senecio Leaves Turning Yellow
Yellowing leaves on Senecio is usually due to an overuse of fertilizer. This succulent stores nutrients and water in its modified leaves, allowing it to stay hydrated and fed for longer periods than tropical houseplants with broad leaves. Over-fertilizing or using too strong of a fertilizer will cause stunted growth and yellowing of leaves due to fertilizer burn on the roots. Only feed senecio once or twice a year, using a highly diluted liquid fertilizer formulated for succulents.
Another reason for yellowing leaves could be an infestation of aphids or mealybugs. Although senecio is fairly trouble-free, insect pests can attack plants stressed from overwatering, overfertilizing, or low light. The leaves may fall off the plant or have a sooty and dirty appearance from the honeydew excreted by the pests. Typically a strong spray of water will rinse the aphids or mealybugs from the plant and treat the problem. Heavy infestations may require the use of an insecticidal soap approved for use on senecio.
Scale insects are sometimes an issue and will be seen on the stems between leaves. These insects look like flattened ovals in white, brown, or black. Use a cotton swab dipped in rubbing alcohol to wipe off the scale insects, repeating as necessary.
The most common diseases in senecios are root rot and powdery mildew. Although both are caused by fungi, they require different conditions to thrive and spread. Root rots are most common when a plant is left to sit in water. The standing water or waterlogged soil reduces airflow around the roots, allowing the fungus to thrive and spread, eventually killing the plant.
Powdery mildew thrives when days are hot and nights are cool. Typically this is seen on houseplants grown in unheated spaces such as on a sunny porch or unoccupied bedroom. The mildew moves quickly when the air is dry and poorly circulating, such as in a greenhouse or dedicated growing area during the winter. The least invasive treatment is to remove all plant parts with powdery white marks. Fungicides formulated for houseplants can be used as a preventative to protect uninfected leaves and stems. Always make sure that any treatment is safe to use on your particular senecio plant.
Senecio Not Blooming
Senecios are not typically grown for their flowers, although they are known to bud during any time of the year in optimal conditions. Most types of senecio will bloom while actively growing in summer. Small white flowers will appear and smell of cinnamon. The blooms will quickly turn into wispy seed bunches that disperse on the wind, similar to a dandelion. The plants are more likely to bloom when they are grown outdoors in their preferred hardiness zones of 9-12. Extra fertilizing will not result in more or heavier flowering and is more likely to damage the overall growth. Day length and temperature are the most important factors in encouraging blooming.
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Author Robbin Small - Published 12-21-2023