Orchids

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Orchids have two main ways of growing:

• Monopodial growth - one, usually upright, axis from which leaves appear.
• Sympodial growth - the axis is a prostrate rhizome from which shoots appear. Many sympodials develop pseudobulbs, thickened shoots from which the leaves grow. These act as storage organs for water and nutrients.
• Within these two broad groups, orchid can be narrowed down to four types:

• Terrestrial orchids - have their roots in soil.
• Climbing epiphytes - found in tree tops, with roots clinging to the bark to absorb nutrients and water.
• Lithophytes - grow on rocks or in very little soil.
• Saprophytes - get their nutrition from dead or decaying matter through symbiotic relationships with fungi.

Epiphytes and lithophytes have thick and fleshy aerial roots that are covered with a spongy, silvery crust called velamen. This protective substance attracts and retains humidity, fixes the roots to rocks or soil, provides insulation against ultraviolet radiation and contains chlorophyll to assist in photosynthesis.
Saprophytes are virtually impossible to cultivate. Some of the world's largest orchids are of this type, such as the genus Galeola, whose stems can reach 18m (60ft) in a matter of days.
Orchid leaves can be deciduous or evergreen, narrow or broad, large or small. Some reach 3m (10ft) long, while others are thin or tough and fleshy. They can be dark or light green, mottled or even silvery.
Orchid flowers have six petals including the labellum, or lip, that makes them so distinctive. In some cases, the outer sepals (which are like petals) have grown together. In the centre is the columna, a protrusion that contains the frequently fused stamens and stigma.
The structure, fragrance and flower colour have one aim - propagation by insects and, in a few cases, animals.
New orchids are constantly coming on the market, but the following genera are easier to grow than other kinds.

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orchid gallery