I Have Red Leaf Spots on My Spider Plants

Ion Poisoning

• Water your spider plant with bottled water if it develops reddish leaf tips or spots, which are caused by a buildup of boron or fluoride ions in the soil and the plant. Do not water your spider plant with tap water if it contains fluoride. Composts containing perlite should be avoided as they leach fluoride ions into the soil. Use a quality liquid houseplant fertilizer as some fertilizers contain fluoride. Spider plants grow best in slightly acidic compost with a pH between 6.0 and 6.5.

Treatment

• Flush out your spider plant's soil with abundant water every two months or as soon as you see any sign of a white crust of the soil surface or see any red leaf margins or spots. This removes any excess salts that have built up in the soil.

Fungus and Bacteria

• Water your spider plant carefully on cold, damp days, taking care to keep the foliage dry. Spider plants are vulnerable to bacterial and fungal leaf diseases that favor damp conditions. If your spider plant develops leaf spots with a reddish margin, move it to a brighter spot with increased air movement. Water your spider plant in the morning during the winter so that it is dry before nightfall.

Spider Mites

• Inspect your spider plant if its leaf undersides are mottled. This, along with fine webbing on the leaves, is a sign of red spider mite infestation. They look like tiny reddish dots that are almost invisible to the naked eye. Mist your spider plant every day, and place its pot on a dish or damp gravel to raise humidity levels and deter red spider mites.