• Any one of a number of problems can cause gardenia leaves to drop.Medioimages/Photodisc/Photodisc/Getty Images
  
  Gardeners can see their gardenias' leaves die and drop off for several reasons. The plant requires specific conditions for growth and survival, with a limited acceptable temperature range. Leaf drop is normal at some point; even healthy leaves eventually die. The University of Florida says some leaf drop is common in spring and fall as temperatures change to cool nights with warm days, but leaf drop in any other condition signifies something is wrong.
  
  

Extreme Conditions

• Excessive watering, heat or dry conditions can all lead to leaf drop on a gardenia plant. Suboptimal conditions lead to the flower buds dropping off as well. This plant is picky and has different light requirements for outdoor and indoor growing. Its preferred daytime temperature range is only in the upper 60s to mid 70s F, and the nighttime temperature should stay at 60 degrees F, notes the University of Rhode Island. Leaf loss occurs from inappropriate nutrient levels or cold temperatures.
  
  

Transplant Shock

• A change in the gardenia's overall environment is enough to send its buds and leaves fluttering to the ground. This results from transplanting the plant or just bringing it indoors after it's gotten used to outdoor conditions. Wherever you move the plant, it requires well-draining soil. Give the plant the attention it needs. B. Rosie Lerner of Purdue University writes in "Purdue Yard & Garden News" that gardenias "won't tolerate neglect."
  
  

Cat Urine

• If you know a cat has been using the area or container where the gardenias are as a substitute litter box, the resulting change in pH in the soil can kill off the leaves. Janet Carson of the University of Arizona's Cooperative Extension Service notes on UAEX's website that this can change both pH and salt levels in soil. She recommends adding sweet gum balls --- the spiky fruits of the sweet gum tree --- to surrounding soil to ward off cats.
  
  

Leaf Spot

• Leaf spot is a disease caused by fungi. Infection by two particular fungi, Cercospora spp. and Phyllosticta spp., can cause leaf drop. The disease shows up as spots on the leaves, hence the name. If the infection is bad enough, it can lead to the gardenia losing leaves.