European orchids cultivation

Europe

The orchids native to Europe, North Africa and the Middle East are all terrestrial, but they grow in a wide range of habitats including woodland, marsh, well drained grassland on various types of soil and dry roadside verges. A few are evergreen, such as the British native, creeping lady's tresses, Goodyera repens which threads its way through the mossy floor of pine woodland, but most are deciduous.

A few British and European orchids have been grown at Kew for many years, planted out in the Rock Garden and woodland areas or as pot plants in the Alpine section. More recently, a wider selection has been acquired and maintained in the Lower Nursery, and these are used for research in the Sainsbury Orchid Conservation Project and sometimes for display. From February to May, when most of them flower, the greenhouse where they are kept is a stunning sight. For ease of cultivation these genera and species are divided into two groups which are related to their natural habitats, in the open or in more shaded situations.

Ophris apifera

Both groups of orchids are easily accommodated in the same greenhouse which is kept frost-free with a winter minimum temperature of 5ºC (41ºF). It is ventilated as much as possible to keep the atmosphere buoyant and fans give good air movement. The house is covered with a 50% shade cloth from April to October. The woodland orchids are provided with extra shading All the plants are potted and stand on slatted wooden staging over a moist gritted bench which can be flooded to raise the humidity while the plants themselves remain dry. Standing the pots on slatted staging also prevents them from rooting into the benches with the consequent possibility of the spread of disease.

Open Habitat Orchids

Orchids which store food reserves in underground tubers include the genera Ophrys, Orchis, Serapias, Aceras and Gymnadenia. A new shoot grows from each tuber during the autumn to form a rosette of leaves in winter or early spring. The plants flower in spring or early summer, then die down and remain dormant for several months. This cycle is well adapted to a climate which is hot and dry in summer, cooler and damper in autumn and winter. Plants in this group originate mainly from the Mediterranean region, although some range as far northwest as Britain, such as the bee orchid, Ophrys apifera, man orchid, Aceras anthropophorum, and the stately lizard orchid, Himantoglossum hircinum.
Aceras anthropophorum

In cultivation the dormant tubers are repotted about 4 cm deep during the late summer. They are watered immediately after repotting and then perhaps once more before the new shoots appear a few weeks later.

Leaf growth is rapid, and by December these orchids have formed a rosette of leaves. Watering through the winter is tricky; as the plants are growing they need a little water but not too much. If it is left on the leaves, water seems to precipitate the development of fungal problems, which can be fatal. Pouring water around the edge of the pot early in the day, so that water does not lie on the leaves overnight, is usually safe. Watering is reduced as soon as the plants come into flower.

Glasshouse culture brings these orchids into flower earlier than if they were growing in the wild. Ophrys fusca, one of the common bee orchids of the Mediterranean region, normally flowers from February to April but starts flowering in early December under glass. Many flowers in the collection are pollinated so that the resulting seeds can be used in research on the propagation of European orchids.

After flowering the plants die down and are kept drier so that by mid-summer a little water may be given only once in four weeks or so. This is needed to keep alive the fungus without which the orchid will not thrive.

Plastic half-pots, 12 cm in diameter, have proved very satisfactory for the majority of European orchids, but some of the larger species grow more robustly in a larger and deeper pot of conventional shape. Each pot is filled one-third full with fresh compost and the next third is filled with old compost from around the tuber. In each pot two or three tubers are bedded into the old compost and then covered with the new mix. The incorporation of some of the old compost is important as it ensures that some of the associated fungus goes with the tuber into the new pot. A certain amount of the fungus mycelium can sometimes be seen on the surface of the tuber but experience at Kew has shown that plants grow more vigorously after repotting if additional fungus is introduced by including some of the old compost too. The new compost provides a good supply of leaf mould and bark for the fungus to feed on for the coming year.

Woodland Orchids

Listera cordata Orchids from the woodlands in the more northerly parts of Europe include the genera Epipactis, Cephalanthera, Listera and Cypripedium calceolus, the lady's slipper orchid. Their annual growth cycle starts in the early spring, when a new shoot grows from each over-wintering bud. Plants flower in the summer and die down in autumn when their seeds disperse. They do not form tubers, but over winter from an underground stem, or rhizome.

These orchids grow best when they are repotted infrequently, grown in larger pots and top-dressed annually to refresh the compost. This minimizes the disturbance to their rhizome and roots. A compost mixture with extra leaf mould is used to simulate a woodland soil and provide a substratum for the fungus. Watering is done rather more frequently than for the tuberous orchids. The pots are kept just moist through the winter and watered more liberally in spring when the buds burst into active growth. They are watered well during the summer and slightly less in autumn when the shoots die off.

Epipactis palustris

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