Soil/Siting

• Orange trees prefer full sun and will grow in almost any soil that drains well, including sandy or adobe clay. Plant trees on the south or southeast side of your house to protect them from the cold. Trees grown in sandy soil will need more frequent watering and fertilizing. Soil pH can range from 6.0 to 8.0. Avoid calcium-carbonate sub-soils or salty soil because trees won't grow well in them.
  
  

Water

• Water newly planted trees two or three times during the first week. For the next few weeks, your tree will need to be watered once or twice a week. After that, water it thoroughly when the soil is dry an inch or two down. Mature trees will probably only need to be watered every few weeks, unless the soil is very sandy.
  
  

Fertilizing

• Orange trees need large amounts of nitrogen, phosphorous, potassium, sulfur and calcium, as well as smaller amounts of other nutrients. In California, Arizona and Texas, nitrogen is usually the only nutrient that has to be added to the soil. Don't fertilize your tree until you see new growth after planting. Consult your local county extension for help determining what kind of fertilizer to use in your region.
  
  

Weed/Grass Control

• Don't let weeds or lawngrass grow under your orange trees because they'll compete with your tree for fertilizer and water. Keep lawngrass about a foot from the canopy of your tree. Grass and weeds can also harbor pests that will damage the fruit. Don't control weeds by using organic mulch because it might introduce foot rot disease to your tree.
  
  

Pruning

• You don't need to prune or train your orange tree since it's shaped and pruned before you buy it. However, if you see any shoots below the scaffold limbs, you should remove them. Freeze-damaged trees may require pruning to save the tree. Commercial growers control the size of their trees by trimming the tops. That way, it's easier and safer to pick the fruit. They may also prune the sides to let more sunlight in.
  
  

Problems

• Most orange tree problems won't kill a tree, and home gardeners can ignore them since they only affect the appearance or size of the fruit, which remains edible. Orange tree pests include mites, aphids, scales, whiteflies and the Asian citrus leafminer. Citrus spray oils can be used to deter them. Orange trees can also develop a fungal infection called foot rot and a virus known as tristeza. Tristeza can kill orange trees quickly, especially ones growing on sour orange rootstock. If pest control is necessary, consult your local county extension agent for help.