How To Spot When Your Houseplant Is Diseased

How To Spot When Your Houseplant Is Diseased

Keep your houseplants healthy and nip disease in the bud

Houseplant diseases are usually caused by either the plant being in a weakened state or by the environment in which the plant is being kept. Make sure there is a good airflow around the plant as fungal infections thrive in stagnant air. Keep on top of deadheading as rotting flower heads are an ideal breeding ground for fungi; also make sure you remove any dead or damaged stems. If you spot any diseases immediately remove the plant from the vicinity of other plants to prevent the disease spreading. Avoid stress in the plant by making sure it is not too wet or too dry and is not pot bound. Overfeeding with a high nitrogen fertiliser also produces a lot of lush, sappy new growth which is attractive to sap sucking insects.



Botrytis (Grey mould)

This is a fungal infection which shows as a fluffy grey mould and thrives in a damp, dark, cool environment. Avoid overwatering and leaving the plant sitting in cold, wet soil and maintain a good airflow. Make sure you cut out any dead or damaged stems and always remove any spent flowers as the fungus’ preferred habitat is dead material. It enters the system through a break in the stem or leaf. Cut out any infected tissue and spray with a solution of bicarbonate of soda (1tbst to 1 gallon water) or a houseplant fungicide; this will only help prevent the infection and cannot cure an already infected plant.

New Guinea Impatiens

New Guinea Impatiens

Powdery mildew

This is a white powdery fungal infection which eventually turns grey and is the result of poor air circulation and high humidity, which is unfortunately the environment its main victims (African violets, gloxinias and begonias) require. Cut out all the infected leaves and flowers; if the centre is particularly crowded take out some more leaves to improve air circulation. Also move to a lighter position. Spray with the soda mixture or a fungicide.


Orange/brown spots on the tops of the leaves and rings on the underside are the symptoms of this fungal disease. It thrives in a wet environment so make sure you don’t overwater. Pelergoniums are particularly susceptible so keep them on the dry side. Treatment is as for Botrytis.

Hibiscus - houseplant


Sooty mould

This is a black fungus which grows on the honeydew secreted by aphids or scale insects so check your plants regularly, paying particular attention to any new soft, sappy growth. If you don’t control the insects the sooty fungus will keep returning. Wash it off with a cloth dipped in a tepid, mild solution of soapy water.

If you would like to know more about keeping your houseplants in tip-top condition read the blog articles or watch the videos on our Youtube channel.

Angela Slater

Daughter of a farmer and market gardener so have always had a connection with the outdoors, whether it was keeping animals or producing fruit, vegetables and cut flowers. Along with my work at Hayes Garden World I also have a smallholding, mainly breeding rare breed pigs. I gained an HND and BSc in Conservation and Environmental Land Management, as a result I am an ardent environmentalist and have a keen interest in environmentally friendly gardening. In my time at Hayes I worked for several years in the Outdoor Plant and Houseplant areas.