Pineapples and other Bromeliads

On the second voyage to the New World in 1493, Columbus and his crew encountered a fruit which they had never seen before. One of them described it as being 'in the shape of a pine cone, twice as big, which fruit is excellent and it can be cut with a knife, like a turnip and it seems to be wholesome'. Its resemblence to a pine cone gave rise to the fruit's English name of pineapple, while its Latin name Ananas came from the word 'nana' which was the local people's name for the plant. People in the Caribbean area at that time valued the fruit highly, placing it outside their homes to welcome visitors. Later, Europeans adopted this habit with the pineapple motif used on gateposts and in carvings.

Where are pineapples grown?

Pineapples (Ananas comosus) are native to southern Brazil and Paraguay, but after the colonisation of the New World, they were rapidly transported to all areas of the tropics. They are now widely grown in tropical and sub-tropical areas with moderate temperatures, such as islands just inside the tropics and on the eastern side of continents. The major producing areas include Hawaii, Brazil, Malaysia, Philippines and the Cote d'Ivoire. Nearly 10.6 million tonnes of pineapples are produced each year (figures for 1988).

What does the pineapple plant look like?

The pineapple plant is a rosette of long fleshy pointed leaves around a terminal bud. Eventually this bud gives rise to the flowering stem. Numerous sessile (stemless) reddish purple flowers, each subtended by a pointed bract (a leaf-like structure), are arranged spirally around the stem. The flowering head is surmounted by a crown of short stiff leaves.

The fruit is formed from the thickened stem surrounded by 100-200 individual fruitlets fused together. Its tough waxy rind consists of the pointed bracts and the remains of the flowers which persist after the fruits are formed. In cultivated pineapples, the fruits are formed parthenocarpically - that is they develop without pollination and fertilisation taking place - and consequently they do not contain seeds.

How are pineapples used?

Pineapples are popular as fresh fruit - the best flavour develops if they are allowed to mature on the plant before harvesting. Much of the pineapple crop is canned as slices and chunks or made into juice. Among the by-products of the pineapple industry is the enzyme, bromelain, used in the food industry, the leather industry and in medicine.

Some cultivars of pineapple are cultivated for the strong white silky fibre which can be extracted from their leaves. In the Philippines this fibre is woven to produce 'pina', a light-weight sheer but fairly stiff fabric, which is often embroidered and used for table linen or clothing.

Other bromeliads

The pineapple is a member of the family Bromeliaceae. This family of some 2000 species, almost entirely restricted to the New World tropics and subtropics, exhibits a great diversity of plant form. Many species have attractive, often brightly coloured foliage, flowers and fruits. They range in size from moss-like species of Tillandsia to the enormous Puya raimondii from the Andes which produces a flowering stem up to 5 m tall.

Most bromeliads are epiphytic - that is they grow supported on other plants but without harming their hosts by abstracting nutrients from them as a parasite would. Many of them grow perched on trees in the tropical rainforests and cloud forests where atmospheric humidity or rainfall is high enough for them to obtain the water they need to survive. The pineapple is fairly unusual in the family in being a terrestrial species. A number of the epiphytic bromeliads, including Billbergia, Aechmea and Neoregelia, are known as urn plants because their overlapping leaves form funnels in which water collects. Plant debris, dead insects and small animals are also trapped in the funnels. The plants absorb both water and nutrients by means of special cells on their leaf bases. Some mosquitoes and tree frogs live in the water contained in the urns.

Air plants (Tillandsia spp.) show extreme specialisation for an epiphytic lifestyle. Their narrow leaves are covered with moisture-absorbing scales which take up water from the atmosphere together with nutrients from dust on the plant. The scales also protect the plant from desiccation. Spanish moss (T. recurvata), which is native from the USA down to Argentina, grows in grey hanging festoons in habitats as apparently barren as telegraph wires. It is harvested for use as packing material, as 'vegetable horsehair' and for use in insulation and in reinforced concrete.

Where are bromeliads grown at Kew?

Most bromeliads, including the pineapple, are grown in the wet tropics section of the Princess of Wales Conservatory. Some species of Tillandsia can be seen in the adjacent cloud forest zone. Other bromeliads are displayed as epiphytes on trees in the Palm House.

Growing conditions

Bromeliads are popular as house-plants because they are relatively easy to grow and many of them have attractive foliage or spectacularly coloured flowers. They grow best in fairly warm humid conditions although their tough leaves enable them to withstand the dry atmosphere prevalent in many houses. Urn plants, which grow wild in the canopy of the rainforest, can tolerate shady conditions, but they must not be allowed to dry out and their water reservoirs must always contain some water.

Many bromeliads can be grown in a standard freely draining potting compost. They need plenty of water during the summer growing season but should be watered less frequently during the winter. Most bromeliads die after flowering but can be propagated from offsets. These should be removed from the parent after flowering, placed in a sandy compost and kept warm and moist until roots have formed.

Air plants simply need support and a bright position to grow. They should be sprayed with water daily and occasionally fed with a weak fertiliser solution. They should not be allowed to stand in water.

Pineapples can be grown from the crown which is cut off the fruit. They should be planted in a well-drained compost and new leaves will appear in the centre when the top has rooted. They should be kept warm and protected from draughts and grown in a well-lit area. In pineapples imported into the UK, the crowns have often been partly removed and these damaged crowns cannot be grown in this way.

Additional sources of information

Cobley, L. S., 1976. An Introduction to the Botany of Tropical Crops,2nd ed., Longman
Jenuwein, H., 1988. Avocado, Banana, Coffee: How to grow useful exotic plants for fun, British Museum (Natural History)
Simmons, J. B, (ed.). 1988. Kew Gardens Book of Indoor Plants, George Philip
Mossman, K., 1977. The Pip Book, Penguin
Purseglove, J. W., 1968. Tropical Crops: Monocotyledons, vol. 1, Longman
Morton, J. F., 1987. Fruits of Warm Climates, Julia F Morton
Samson, J. A., 1980. Tropical Fruits, Longman

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