Pineapple is a member of the bromeliad family. A pineapple plant grown in fields can mature in 18 months, but an indoor pineapple plant typically takes 24 to 30 months to reach the stage where it can flower. Even after your pineapple plant reaches maturity (it should be at least 24 inches tall), you may still need to force it to flower, which you can do by exposing the plant to the ethylene gas produced by ripe apples.
Place two ripe apples, or cut pieces of apple, in the pot with the pineapple plant.
Cover the pineapple plant and the apples (or the apple pieces) completely in a clear plastic bag. Seal the bag and set the covered plant in a shaded area for four to five days.
Unseal the bag and remove it from the pineapple plant and the apples. The pineapple plant should flower in two to four months.