Pineapples (Ananas comosus) grow above ground but not on trees. Pineapple plants are bromeliads, which are perennial plants. Pineapple fruits grow at the ends of the plants' stems. In U.S. Department of Agriculture plant hardiness zones 11 through 12, pineapple plants grow outdoors year-round. Some varieties tolerate slightly cooler temperatures, and with care, pineapple plants can grow indoors and produce fruit.
Medium-sized shrubs, pineapple plants grow in clumps of sword-shaped leaves. These leaves grow in rosettes from the base of the plants and reach about 3 feet long. Flowers and fruits can add another 1 foot of height, and plants grow 3 to 4 feet wide. Pineapple leaves are evergreen and gray-green, and the edges are saw-toothed.
Before flowering, stems at the center of the rosettes grow longer and larger, and large clusters of 50 to 200 purple or red flowers appear at the stem ends. Pineapple fruits are formed from the fusion of many flowers. Plants usually produce one to two fruits.
Vegetation from pineapple plants provides material for new plants. Four types of vegetation can grow into new pineapple plants: The crowns of fruits; shoots that appear on the stalks below fruits; suckers that grow at leaf bases; and ratoons, which are secondary stalks from the underground parts of stems.
Home gardeners usually use the crowns of store-bought fruits to propagate pineapple plants. Attractive ornamental plants, pineapple plants can grow outdoors in most areas of the United States in summer, but they must be brought inside when temperatures fall below 60 degrees Fahrenheit later in the year.
In USDA zones 11 through 12, pineapple plants produce fruit in 18 to 36 months. Sandy or loam, moderately fertile soils and full-sun sites at least 5 feet away from trees or other large structures provide the best growing conditions where pineapples produce large, healthy fruit. Plants don't tolerate flooding, and drought conditions reduce fruit production.
"Smooth Cayenne" (Ananas comosus "Smooth Cayenne") is a spineless pineapple plant, which makes it useful for planting in high-traffic areas. Another variety suitable for home gardens is variegated pineapple (Ananas comosus var. variegatus), an ornamental plant that carries gray-green, yellowish-white striped leaves. "Smooth Cayenne" is hardy in USDA zones 10 through 12, and variegated pineapple is hardy in USDA zones 11 through 12.
Pineapples grow indoors in heated greenhouses and as houseplants in containers. Containers for pineapple plants must have drainage holes. To grow pineapple plants from crowns, remove all traces of fruit and leave the crowns to dry for one or two days. Place them in water or moist potting soil until roots appear, and plant them in containers filled with potting soil formulated to grow bromeliads.
Indoor pineapple plants need bright conditions, high humidity, constantly moist soil and temperatures that never fall below 65 degrees Fahrenheit. Indoor pineapple plants take three to four years to produce fruit, and the fruits are usually small and not tasty. Containers and indoor conditions restrict the plants' size, so that indoor plants don't grow as large as plants grown outside.