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24 November 2009
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Orchid

Orchids

Not all orchids require steamy hothouse conditions. Many can be easily grown on a sunny windowsill.

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The orchid family includes 20,000 to 30,000 species and more than 70,000 hybrids or cultivars. The largest number, and most popular, come from Asia. South America is also rich in wild orchids.

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.

• Cattleya : sometimes known as the 'Queen of orchids'. Blooms come in white, yellow, pink, purple, cream and reds, with just one or two rigid and leathery leaves. Temperate or warm epiphytic plants.
• Cymbidium : the most familiar and probably most widely cultivated genus, with long, narrow, rich green leaves. Although they can grow in trees, they're terrestrial orchids. The cut flowers and blooms last up to two months.
• Dendrobium : can be evergreen or deciduous, producing large sprays of flowers in a vast range of colours. Epiphytes with long pseudobulbs that resemble bamboo.
• Miltoniopsis : pale green and soft leaves that are easily damaged. Commonly called the pansy orchid because of its distinctive flowers.
• Ondontoglossum : evergreen orchids in virtually any colour, with intricate markings and patterns on the flowers.
• Oncidium : the dancing lady orchid is an evergreen species with distinctive mottled markings or patterns.
• Paphiopedilum : the slipper orchid has broad, dark green or sometimes mottled leaves. The flowers, which can be spotted or striped and are sometimes hairy, appear at the top of long upright shoots.
• Phalaenopsis : the elegant moth orchid is one of the most beautiful with fleshy leaves and flowers in a huge range of colours.

When buying orchids, make sure you check their needs, as they vary greatly. Choose hybrids rather than wild species, as they're easier to grow.

Site and soil preference

Give orchids bright light but not hot sun, and humidity levels of around 65 per cent. When it's sunny outside, the indoor plants like being misted. Avoid too dry an atmosphere in winter.

Check the temperature range for your chosen orchid. Make sure they get fresh air now and then, but don't leave them in a draughty spot.

Keep the plants away from fruit bowls as the gas released by apples makes buds and flowers drop.

Create a microclimate that will suit your orchids by grouping them with other plants that like the same conditions, such as bromeliads and ferns.

Watering and feeding

When new shoots are emerging in late winter and spring, orchids need more light and water. However, remember that over-watering is the easiest way to kill an orchid. Most like their growing medium to be a little moist, but not soaked.

In summer, when they're growing nicely, orchids need nutrients, water and warmth. In late summer and early autumn they need plenty of light and a gradual reduction in water.

From late autumn into winter, when they're resting and then flowering, they need more light but very little water.

Use only food or fertilisers made specially for orchids, and only apply when the orchid is in active growth.

Orchids suffer the same problems as other plants, such as aphids, red spider mites, viruses, slugs and snails.

However, the majority of problems are caused by us. Avoid giving too much or too little light, water or nutrients, extremes of temperature and so on.

National Collection of orchids:

G Hands
c/o NCCPG, 12 Home Farm
Loseley Park, Guildford
Surrey GU3 1HS
Tel: 01202 480529
Website: (External) www.orchidsandmore.org.uk

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