Terrestrial orchids are ground-dwelling orchids and are widespread throughout Australia. A wander through bushland in winter or spring will usually reveal a number of species of terrestrial orchid to the keen observer, some of the best-known kinds being Greenhoods, Sun-Orchids and Donkey Orchids.
In Southern Australia, most terrestrial orchids emerge from dormant underground tubers with the advent of autumn rains. After a period of growth, flowering generally occurs in winter or spring, depending on the species. Several months after flowering, the orchids will die back to their underground tubers and remain dormant through the dry summer period until the cycle resumes again with autumn rains.
The most easily-grown species are those which rapidly multiply their underground tubers to form colonies, such as is the case with many of the Greenhood species (especially Pterostylis nutans). These can be grown in the garden in a good friable soil in semi-shade.
Slugs and snails are major pests of terrestrial orchids and plants should be protected using Multiguard Snail and Slug Pellets, or other environmentally friendly products.
Cultivation of terrestrial orchids is generally much more reliable in containers where the environment can be more readily controlled.
Following flowering, when the leaves go yellow then brown and dry up in late spring or summer, let the pot dry out completely. At this stage, the pot may be knocked out and the tubers repotted in a potting mix composed of 50% coarse river sand, 20% peat moss and 30% partly decayed eucalypt leaf mould.
The pot should be kept in a cool, shaded spot until towards the end of February when watering may be recommended. As the orchids emerge from summer dormancy, keep the potting mix moist at all times. All species like good air circulation. Some species prefer heavy shade, others full sun, but most will adapt to a wide range of light intensities. Provision of 50% shade, either with shade cloth or under trees, will be satisfactory in most cases.
Some species are very sensitive to fertiliser. Chiloglottis, Diuris and Pterostylis are very hardy and will benefit from weak applications of foliar feed in the early stages of growth. Peters Excel is a particularly safe liquid fertiliser.