Plants often seen in high places

'Tillandsia' and 'Nidularium' growing epiphytically. Photo by Gerard O'Brien.
'Tillandsia' and 'Nidularium' growing epiphytically. Photo by Gerard O'Brien.
Epiphytes are one of the most amazing groups of plants because they do not need to have their roots in the soil to grow.

Most live high up attached to sturdier plants or structures. Small plants growing high in the canopy can avoid competition for light from other plants, and the attentions of browsing herbivores.

Epiphytes do not take nutrients or water from the tree the way parasitic plants do; they take nutrients from the air, falling leaves and debris, rainwater and humidity in the atmosphere.

Many mosses and lichens are epiphytes, as are many ferns, bromeliads and orchids.

Other genera such as Rhododendron have many species that grow as epiphytic plants in their natural habitats.

Most epiphytic plants are found in tropical and sub-tropical mountain rainforests where the humidity is high, but here in New Zealand, in a temperate climate, we have plenty of epiphytic plants in our moist city forests and national parks.

• More than half the 20,000 known species of orchid are epiphytic.

• Evolution has provided epiphytic plants with many ways of collecting water and nutrients.

• The seeds of many epiphytes are dispersed by the wind, while other epiphytes have berries that contain seeds which are eaten by animals and later excreted.

By such ways seeds find conditions in which to germinate. Some plants start out as epiphytes then send roots down into the soil, such as the New Zealand northern rata.

Others have no roots at all and take up nutrients and moisture from the atmosphere, such as Spanish moss.

• Epiphytic orchids and bromeliads can be seen growing in the central house of the Winter Garden attached to some of the small trees and climbers.

- Stephen Bishop is curator of the Winter Garden Collection at the Dunedin Botanic Garden.

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