Causes

• Brown bases on the the leaves of spider plants are caused by fungi that rot the roots, stems and base of the plant. The fungi thrive in and spread on water, which is why overly wet soil is the primary cause of this problem. It is common for home gardeners to over-water spider plants. If your container does not have drainage holes, the water may build up and saturate the soil, leading to the development of rot diseases.
  
  

Symptoms

• Spider plants suffering from root or crown rot will evidence brown bases on the leaves. These areas may be soft to the touch, or wet and rotten. The leaves may pull away easily from the plant. If the brown areas are on the tips of the leaves only, this signifies an entirely different problem caused by the buildup of certain minerals (fluoride in particular) in the soil. In addition, exposure to the hot, direct rays of the sun will cause brown spots on the leaves, but again, they will be on the tip or upper surface of the leaves and not the bases.
  
  

Treatment

• Successful treatment depends on how much of the spider plant is damaged. If the roots are destroyed, it is best to throw away the plant and start over with a new one. If only part of the plant is affected, cut away the rotten parts. Re-pot the remaining plant in loose, well-draining soil and in a container with drainage holes.
  
  

Prevention

• Prevention is the best cure for rot on spider plants. Only water your plant when the soil has dried out from the last watering -- not so that it is bone dry, but so that the surface of the soil feels dry to the touch. Locate the plant in an area where it will receive at least a half-day's worth of indirect sunlight each day, and keep it warm and away from cold drafts.