Pineapple was propagated vegetatively in improved forms by the Central and South American natives long before the discovery of the continent by Europeans. Then it was rapidly spread throughout the world and is now grown everywhere in the Tropics, to which it is adapted. In the United States it can be grown only in the warmest areas of the Fla. peninsula, and in well-protected garden sites along the southern Pacific coastal strip. It is a principal crop of Hawaii, and a minor one in Fla.
The plant is a herbaceous, perennial mono-cotyledon. It has a short stem or stalk, covered by the narrow sword like leaves in a tight spiral; the stem, at the time of floral differentiation, bears numerous flowers in a tight spiral just below the growing point, which continues and forms a spiral of smaller leaves above the flowering portion of the stem, known as the crown. The plant is about 3 ft. tall, and if not crowded it will spread 4-5 ft. or more with age.
The exact hardiness for the Pineapple are not truly known; in the open it has been seriously damaged at temperatures of 32° F., but under lathe or cover, plants have been reported to withstand as low as 25° F. for short periods. However, fruit is injured by a few hours below 41° F.
Three parts of the plant are commonly used in propagation. The crown, borne on top of the fruit; slips, which develop at or near the flowering stalk, and shoots or suckers, which develop in the axils of the leaves, or from below ground. Taken from the mother plant, usually after the harvest, they are dried for a week to a month before planting. They are planted upright in dibbled holes 4 to 6 in. deep. Slips are usually preferred then suckers and crowns last. An alternative method is to take the leaves from a stem, cut it into 2 or 3 portions, burying these in the soil 5 or 6 in. deep.
Planting distance in multiple plantings varies considerably, but the plants can be grown close together, as 22 in. x 22 in. in beds of several rows.
The primary concern in developing quality fruit of good size is to keep the plant growing vigorously. Up to 70 or 80 leaves should be developed before flowering to secure good fruit size; this can be obtained only with heavy fertilization. On sandy soils a pound or more of a 6-6-6 formula applied at 3 or 4 evenly spaced applications through the year are generally needed. In addition, extra nitrogen in the winter and summer is often used. A fertilizer which contains other elements, such as magnesium and trace elements, will probably give excellent results, as pineapples suffer many micro-nutrient deficiencies.
Foliar feeding is particularly easy with the Pineapple, for the basal portion of each leaf is adapted to absorb water and nutrients. A spray of 1 lb. of urea, 12 oz. of potassium sulfate, 8 oz. of calcium nitrate and 4 oz. of iron sulfate, magnesium sulfate, and calgon, plus a teaspoonful of borax, and a small amount of copper sulfate per to gal. of water sprayed on the plant at biweekly intervals will satisfy its internal needs.
Pineapples are not too particular as to soil, except that it must be well drained; light sandy soils are best, but will require greatest fertilization. Watering should be shallow, with mulches recommended to keep down weed competition and hold water near the surface of the soil.
Pineapple does well in full sun if maximum temperatures are not too high; it can also be grown quite satisfactorily in partial shade. It should not be planted exposed to winds, as the heavy fruit and shallow root system make it particularly subject to blowing over.
As the inflorescence appears, the flowers open from the base toward the tip, taking about 20 days to complete. The petals are violet or purplish, and wither after bloom. All pineapples are self-incompatible (will not set seed with their own pollen) so that the fruit on an isolated plant or a field of the same variety develops without seed forming. The edible portion of the fruit is made up of the fused bract, corolla and ovarian portions of the flower, the petals and stamens having dried and dropped, and is a sorosis. If cross-pollinated, hard, bony seeds form in the ovary, deep in the flesh.
The Pineapple may be induced to bloom rather easily by spraying the central growing point with naphthalene acetic acid (NAA). It seems to be a little more effective if applied during cool weather, and hence might be used as a spring spray to insure fruit development through the best part of the summer. It should not be used unless there are sufficient leaves on the plant to bring the fruit through in best condition and size. Commercially it is used primarily to induce all of the plants to bloom at the same time, so that harvest is simpler. The single flower cluster emerges from the basal rosette of leaves and matures 15 to 32 months from planting. If, after harvest, the original plant is left in place, flowering occurs annually in the so-called ratoon crops which follow. Ratoon crops have more than a single fruit, but not more than 2 or 3 should be avowed to develop. The plant will exist for many years, although in commercial practice — fields are taken beyond the first or second ratoon crop, because the fruits tend to be smaller and less perfect.
Temperature affects the time of first fruiting to a marked degree. Slips planted in the fall seldom fruit until the second summer following. Crowns will probably take somewhat longer to develop a good plant than slips. Drought and adverse weather during the year may delay the appearance of the inflorescence the next season, or cause it to be smaller than normal. Time from flowering to ripening is lengthened by cool weather. Thus, though fruits usually mature in summer, they may be delayed until exposed to damaging winter temperatures.
There are numerous varieties of Pineapple. ‘Cayenne’ is the main commercial variety of Hawaii, and is sometimes used in Fla., but ‘Red Spanish’ and ‘Abachi’ are preferred there.
The latter has a rich flavor and is yellow fleshed; ‘Red Spanish’ is more acid and less sweet, with yellowish-white flesh. Nematodes may devitalize the plant; fumigation of the planting site will be beneficial. Mealy bugs, thrips and mites also attack the plant, especially the former. A water spray of malathion will control mealybugs; sulfur dusts most thrips and mites. Control of ants will minimize mealy bug attacks. Weeds are perhaps the greatest enemy of Pineapple. Paper and black polyethylene sheets, or mulches may be used beneficially to keep weeds down in a close-planted bed. Hoeing should be as shallow as possible.