Australian Terrestrial Orchids

Australia is home to a remarkable range of terrestrial orchids, many of which can be successfully grown in the home garden when their natural conditions are understood. These ground-dwelling orchids include species such as Pterostylis baptistii (pictured), one of the well-known “Greenhood” orchids.

Unlike tropical orchids, Australian Terrestrial Orchids grow in soil and follow a distinct seasonal cycle. With the right approach, they are not especially difficult to grow and can provide unique flowers through the cooler months when little else is in bloom.

At a Glance

• Botanical group: Australian terrestrial orchids
• Common genera: Pterostylis, Diuris, Thelymitra
• Plant type: Deciduous terrestrial orchid
• Height: 10 cm to 50 cm
• Flowering: Winter to spring
• Light: Part shade to full sun depending on species
• Soil: Well-drained, low-nutrient, organic-rich
• Watering: Moist during growth, dry during dormancy
• Dormancy: Summer
• Difficulty: Easy to moderate

Types of Australian Terrestrial Orchids

A wide range of species can be found across southern Australia, particularly in lightly forested and open woodland areas.

Among the most recognisable are the Greenhoods (Pterostylis species), with their distinctive hooded flowers. Sun Orchids (Thelymitra) are another fascinating group, opening only in warm, sunny conditions. Donkey Orchids (Diuris) are also popular and are considered among the easier types to grow.

In the wild, these orchids are often overlooked. The foliage can be difficult to spot, and the flowers, while intricate, are sometimes small and well camouflaged.

Growth Cycle

Understanding the natural growth cycle of Australian Terrestrial Orchids is the key to success.

• Summer: Plants remain dormant as underground tubers, allowing them to survive dry conditions.
• Autumn: With the arrival of seasonal rains, new shoots emerge from the tubers.
• Winter: Active growth continues, with foliage developing steadily.
• Spring: Flowering occurs, followed by a gradual decline as temperatures rise.

As the soil dries into early summer, the plant retreats back into dormancy and the cycle begins again.

How to Grow Australian Terrestrial Orchids

To grow these orchids successfully, it is important to replicate their natural habitat as closely as possible.

• Light: Most species prefer dappled shade similar to open woodland, although some (such as Thelymitra) require more direct sun to flower well.
• Soil: A free-draining soil is essential. These orchids prefer low-nutrient conditions enriched with organic matter rather than heavily fertilised soils.
• Watering: Keep the soil lightly moist during the active growing period from autumn to spring. Reduce watering as plants enter dormancy and keep soil relatively dry over summer.
• Position: Good airflow is beneficial, particularly in humid conditions.

These orchids also form a natural association with beneficial soil fungi, which assist in nutrient uptake. For this reason, overly disturbed or heavily treated soils can reduce success.

Growing Australian Terrestrial Orchids in Pots

Many growers prefer containers, as they allow better control over moisture and soil conditions. Pots can also be moved into prominent positions when plants are in flower.

Container growing is often easier than garden cultivation, particularly in areas with heavy soils or unpredictable rainfall.

Potting Mix for Terrestrial Orchids

Choosing the right potting mix is important for long-term success.

A simple approach is to use a quality Australian native potting mix with around 25% added perlite for improved drainage.

A more specialised mix can also be used:

• 1 part native potting mix
• 1 part leaf mould
• 2 parts coarse gravel (around 2 mm)
• 1 part aged eucalyptus mulch (pre-soaked)

A small amount of blood and bone can be added, although fertiliser should be used sparingly.

Each component plays a role, with gravel improving drainage and organic materials helping retain just enough moisture without becoming waterlogged.

Repotting Australian Terrestrial Orchids

Repotting is usually required every two to three years and should be carried out during the dormant period in summer.

• Remove the tubers from the old potting mix.
• Fill a clean pot to within 4 cm of the top with fresh mix.
• Place tubers on the surface with the growing points facing upwards.
• Cover with around 2 cm of mix.
• A top layer of casuarina needles can help replicate natural conditions.

Avoid watering immediately after repotting. After a few weeks, begin light watering, increasing as growth resumes in autumn.

Growing Terrestrial Orchids in pots and containers

Most collectors of Australian terrestrial orchids choose to grow them in containers where they not only have control over the growing conditions but also can bring the containers into view when flowering. Container growing offers a number of advantages and few problems as well.

Australia has a wide range of terrestrial orchids, many are easy to grow and some are very difficult. Given the right conditions you should be able to grow a good range in the home garden.

1. Most Australian Terrestrial Orchids are dormant during the drier months of the year, they also have interesting relationships with the soil fungi. These two condition, dryness at the right time of year, and soil fungi are ate major key factors.
2. Nearly all of the terrestrial orchids have a tuber a bit like a small potato. One species is even called the Potato Orchid (Gastrodia sesamoides).
3. Most are dormant over summer, which is the dry period, and are therefore fairly drought tolerant.
4. They spring into life in autumn when the first rains encourage them to shoot. Some sending up leaves, some a single leaf and then the flower shoot.
5. This active growing period continues through to spring and into summer when the soil begins to dry again and they go back into dormancy.

Growing medium or Potting Mix for terrestrial orchids

Many gardeners will grow these orchids in pots and selection of potting mix is most important.

An Australian Native Potting Mix with 25% added perlite suits many species.

• You can also try a more elaborate mix such as1 part Native Potting Soil
  1 part Native Leaf Mould
  2 parts 2 mm Gravel
  1 part Euci mulch soaked for 6 hours in water.
  An added tablespoon of blood and bone.

In this mix 1 part represents a 2 litre pot full

Common Problems

While generally reliable, a few issues can arise:

• Snails and slugs can damage new growth quickly.
• Excess moisture during dormancy may cause tuber rot.
• Failure to emerge in autumn is often linked to incorrect watering timing.
• Poor flowering may result from insufficient light.

Maintaining the correct seasonal conditions is the best prevention.

Additional Notes

Nearly all Australian terrestrial orchids grow from underground tubers, similar in appearance to small potatoes. One example is the aptly named Potato Orchid (Gastrodia sesamoides).

Some species remain evergreen, although most follow the typical summer dormancy pattern.

There are around over 115 genera and around 1,300–1,500 terrestrial orchid species native to Australia

A Note on mycorrhizal fungi

Many Australian terrestrial orchids need a special soil fungus to grow properly. In nature, this mycorrhizal fungi lives around the orchid’s roots and helps the plant get nutrients and water. Orchid seeds are so tiny they usually cannot sprout without this fungus.

When growing these orchids in pots, the fungus needs to stay alive in the potting mix along with the orchid. Because of this, these orchids often need very specific potting mixes, watering patterns, and care methods to keep both the plant and the fungus healthy.

To grow them successfully in pots, you need to care for both the orchid and the fungus.

Practical meaning for growers:

• Use the correct native terrestrial orchid mix.
• Avoid sterile or heavily treated potting media.
• Don’t overuse fungicides — they may kill the helpful fungus.
• Repot carefully so some old mix (containing the fungus) stays with the plant.
• Follow the orchid’s natural wet/dry seasonal cycle.

Examples of strongly fungus-associated Australian terrestrials include genera such as Caladenia, Drakaea, and Pterostylis.

Native potting mixes are suited to growing our orchids but for expert advice try joining one of the Australian Native Orchid or Plant Societies.  You will find a wealth of practical experience far exceeds the advice we can give.

Australian Terrestrial Orchids Species In Detail

Some Popular Genera of Australian Native Orchids

• Acianthus (Pixie Caps / Mosquito Orchids)
• Caladenia (Spider Orchids / Fingers / Waxlips)
• Calochilus (Beard Orchids)
• Chiloglottis (Bird Orchids)
• Corybas (Helmet Orchids)
• Cryptostylis (Tongue Orchids)
• Diuris (Donkey Orchids / Golden Moths)
• Dipodium (Hyacinth Orchids)
• Eriochilus (Parson’s Bands)
• Glossodia (Waxlip Orchids)
• Microtis (Onion Orchids)
• Prasophyllum (Leek Orchids)
• Pterostylis (Greenhoods)
• Thelymitra (Sun Orchids)

A Few Rare but interesting Genera to look for

• Spiranthes (Spiral Orchids)
• Cyrtostylis (Gnat Orchids)
• Lyperanthus (Rattlebeak Orchids)
• Burnettia (Lesser Antorchids)
• Rhizanthella 5 species only and all live underground R.gardneri (Western underground orchid) being the best known

Further Information

• Orchid Clubs and Societies
• Australian Native Orchids