There are seven common reasons your plant may be showing yellowing leaves
Every plant species and genus has specific needs; If they are not properly met your plant can suffer
OVER-WATERING
Watering problems account for most of the yellowing leaves
When we saturate plant roots for a long period of time we drown them
Be sure to follow the correct watering schedule for your specific plant
UNDER-WATERING
Under watering is especially common in older plants that are root bound and cannot hold water around the roots
Pruning, re-potting, propagating, and fresh soil are all good practices for a dehydrated plant
EXTREME TEMPERATURE CHANGES
Most plants can acclimate to changes in temperature, but too quick a change will shock the plant, and too drastic a change can kill the plant
Take care to prevent drastic changes in temperature for your plants
HUMIDITY AND DRAFT PROBLEMS
Air conditioning, heat vents, open doors, entry ways and windows are all places to avoid with sensitive plants
You need to know your plants specific needs
PLANT PESTS
Plant pests like spider mites, thrips, aphids, scale, and mealybugs all do leaf damage to your houseplants
Leaf yellowing is one of the signs of pests damage to your plants
FERTILIZER BURN
Incorrectly watered roots over time can have trouble absorbing and distributing nutrients from fertilizers through the leaves, so you may see yellow leaves with dry brown patches
WHEN YELLOW LEAVES ARE NORMAL
Natural leaf yellowing and shedding can occur on some plants
If the plant appears otherwise healthy and occasionally drops a leaf this may be perfectly normal for your plant