Over-watering
- Brown or black spots on leaves
- Stems look mushy
- Plant is wilted
- Soil feels wet
Under-watering
- Plant is wilted
- Soil feels dry
Insects
- Holes in leaves
- Chewed leaves, distorted leaves
- Pin-size holes in stem
- Back of leaves look silvery with tiny black spots
- Leaves look rusty
Fertilizer
- Too little fertilizer – stunted yellow growth
- Too much fertilizer – leaves have brown, damaged looking edges, leaves may turn black
- A slight excess can cause rich lush growth, usually with no flowering which can suffer damage at onset of cold
Microorganisms
- White powdery substance on the leaves
- Browning and spotting of the leaves
- Other Plant Problems
Animals
- Bark stripped off trees and shrubs
- If top of plant dies for no apparent reason, roots may have been eaten by grubs or gophers
Tree Graft
- Union may not be compatible; though the tree has appeared to thrive for several years
- Tree goes into unexplainable decline
These are just a few of the things which can damage otherwise healthy plants. Hopefully these general guidelines will head you in the right direction to alleviate the problem and prevent future ones!