Growing Culture

• Grapefruits require deep, quick-draining soil, and do well in a combination of quick-draining soil or loam mixed with organic compost. The compost provides long-term nutrition for the trees.
  
  

Fertilizer

• Grapefruit trees require adequate nutrition levels to grow and bear their fruit, but suffer from over fertilization. Gardeners should use slow-release, fruit-specific fertilizers for Duncan grapefruits. The Center for New Crops and Food Products recommends that gardeners use little to no nitrogen, as it may warp the fruit.
  
  

Season

• Gardeners should fertilize their Duncan grapefruit trees in early spring, before the growing season begins. This will encourage new growth and give the tree resources for both blooming and fruiting.
  
  

Frost Dates

• In Central Florida, the last frost date may range from early to late March. Fertilization should take place at least two weeks before this date. Early feeding is especially important for Duncan grapefruit trees, which bear their fruit early to mid-season.