Fertilizing a pineapple plant is a scheduled, regular activity. Unlike many plants that need fertilizer once or twice a year, the bromeliad-related pineapple (Ananas comosus) needs regular applications of a balanced fertilizer, less frequent applications of micronutrients, and depending upon the growing area's pH, iron treatments. Pineapples like slightly acid, well-drained soil and full sun. The pineapple does not like freezing temperatures.
Pineapples should be planted in 1-gallon pots to start. Move up in size as the plant grows, eventually ending with a 5-gallon container for a mature plant. For any container, make sure drainage is adequate. Since pineapples are very sensitive to cold, place pots outside only after all danger of frost has passed. For the first few days, acclimate the pineapple by keeping it in partial shade. This will help prevent leaf burn.
Pineapple plants should receive balanced fertilizer applications every two months for the first year, for a total of six fertilizer applications. According to extensive instructions in "Pineapple Growing in the Florida Home Landscape" from the University of Florida Horticultural Sciences Department, a mixture of dry or foliar 6 to 10 percent nitrogen (N), 6 to 10 percent available phosphoric acid (P), 6 to 10 percent potash (K) and 4 to 6 percent magnesium (Mg) will provide basic fertilizer for the pineapple. For fertilizer application amounts, use 1 to 2 ounces the first two feedings (four months), 1 to 3 ounces at the third and fourth feeds, and 2 to 6 ounces for the fifth and six feeds during the first year. If you are using a higher 10-10-10 ratio, go with the lower end amount (use one ounce, not two). If you are going with a 6-6-6 combination, apply the higher amount.
Micronutrient fertilizers are needed three times a year--May, July and September. Zinc and manganese are usually in these foliar sprays. Iron is also sometimes present. Follow label directions for proper mixing and application. The goal is to get the micronutrients to the pineapple and not burn the leaves. When spraying, spray away from yourself, and try to spray on the plant and not the surrounding deck or furniture.
Pineapples in high pH (more than 7.5) soils will need six applications of iron each year. Pineapples like slightly acidic soil, so adding iron is very important if the growing medium is slightly alkaline. This can be applied at the same time as the NPK fertilizer is added. For a soil drench, use chelated iron. For a foliar spray, iron (ferrous) sulfate is recommended.
Pineapple fertilizer applications for year two of plant growth follow the six-times-a-year schedule of year one. If needed, iron drenching also follows the six applications every other month. In year two, fertilizer amounts increase to 3 to 6 ounces of NPK for months 12 to 16, then 5 to 8 ounces with months 17 to 24. The micronutrient spray regimen should also continue in year two, with three applications during the warm season, usually May, July and September.