Steve Howard writes cultural notes for Adelaide conditions. These are his notes for August; for both epiphytes and terrestrials.
Pots weekly. Small pots twice weekly depending on weather. Drier conditions for hot cold types. Terrestrial pots can dry out faster on warmer days so keep a watch on conditions.
Epiphytes: Recommending feeding towards months end as days lengthen. Many plants in strong spike growth and flowering now.
Terrestrials generally don’t need to be fed although weak organics like Seasol and Powerfeed applied in low doses can benefit colony type greenhoods.
PESTS AND DISEASES
Epiphytes: Botrytis will rot new buds in cold damp weather as fast as it attacks new growths from now. Aphids will increase sharply this month and favour new growth and spikes. Pyrethrum sprays eco friendly and work well, so does a hose but dry spike straight after.
Some terrestrials will rot this month if conditions have been too wet or stagnant over winter. Note this for next season and add more drainage if this has been an issue.
Epiphytes: Keep flowering plants under cover to enjoy. Soon will be the time to start thinking about re-potting and division as spring nears.
Keep flowering terrestrials out of strong winds and heavy rains as flower stems on some varieties are quite weak when grown in cultivation
Later August will produce some warmer drying days as spring nears. Ensure small pots and plants don’t dry out at this time. Good time to check out seedling lists and prepare orders to ensure your plants arrive at the commencement of a new growing season.
Maintenance throughout the year
- During summer, very lightly water surface of pots weekly to prevent tuber desiccation especially if dormant seedlings are in the pot.
- Divide overcrowded pots in summer. Tip out and break into slices like cutting a cake. Stand a slice in a new pot & fill spaces with fresh mix. Take care to keep the surface layer at the surface of the new pot.
- Add fresh leaf litter to surface layer in January to February to March.
- If surface moss gets too thick, peel it off and discard in summer.
- Start heavier watering of pots weekly from mid March.
- Mix seed with fine dry sand and sprinkle on mother pots in April.
- Water as required in autumn, winter & spring so that pots never dry out during the growing season yet are not soggy wet.
- Leaves appear from Anzac Day to June.
- Look for flower buds down inside the largest leaves from mid July onwards.
- Look for new seedling leaves from August to October.
- Enjoy and photograph flowers September to November.
- Hand-pollinate flowers in September – October. Flowers collapse within days of fertilisation.
- Collect seed pods as they turn brown just before they split open in November – December.
- Dry & store seed over summer in paper envelopes kept indoors.
- Allow pots to slowly dry out in mid – late November to induce dormancy and ripen tubers. Plants die down completely in summer to underground tubers.
For further information on growing fungus – dependent orchids refer to:
- ‘Orchids Australia’ February 2006, P58, or ‘The Orchadian’ Vol 15, Number 3, March 2006, P100.
Caladenia latifolia cultivated by LN (Fast Multipler)
Terrestrial Orchid Cultural Groups
Terrestrial orchids can be placed into one of three groups that have similar cultural requirements.
- Fast multipliers with an annual increase rate greater than 1.5
- Slow multipliers with an annual increase rate less than 1.5
- Fungus dependent orchids survival rate less than 1
Fast multipliers (FM):
Fast multipliers are the easiest deciduous terrestrials to grow and potfuls are regularly seen at orchid meetings and shows. They multiply rapidly by forming 2 – 4 tubers per plant each year. They will take some fertiliser and grow better if repotted annually. It is usually not commercially viable to grow seed of these in flask. They will grow well in premium potting mix from your local hardware store with some sand added. This group contains many genera including Acianthus, Chiloglottis, Corybas, Cyrtostylis, Diplodium, Leptoceras, Microtis, Pterostylis and some species from Caladenia, Diuris and Thelymitra.
Slow multipliers (SM):
Slow multipliers are not so easy because there is less room for error. Some very showy Diuris, Pterostylis and Thelymitra fall within this group. A few have a near zero increase rate and will fade away unless additional plants can be produced to make up for occasional losses from predators and disease. They are more expensive because they have to be raised from seed in flasks. Flowering plants are hand pollinated and the seed collected just before the pods split open and the dust-like seed blows away. The pull-off-the-tuber method can be used with some Diuris and Pterostylis species to double plant numbers annually. Do not fertilise these except when repotting. Those with large tubers such as Thelymitra nuda and Diuris behrii should be the first to be repotted in November – December.
Fungus dependent orchids (FD):
Some of Australia’s most fascinating orchids rely on a symbiotic fungal association to obtain nutrients from the soil as these orchids have virtually no roots. The majority of Australia’s terrestrial orchids are in this group and many are rare plants as they seldom multiply. We talk about survival rates for these orchids that are normally less than one. Propagation is from seed. They have a reputation for being difficult to grow in pots. However some species have been kept alive in pots for nearly 30 years. Never use fertiliser because it can kill the fungi. They should be repotted only when the tubers reach or come out of the bottom of the pot or seedlings get too crowded. A new thin layer of leaf litter is added to the surface each summer to feed the fungi which is active near the surface. Flowers are hand pollinated to get seed. Seed is sprinkled on the pots each autumn and with good culture, seedlings will appear in spring around mother plants.
Since the fungus cannot be seen with the naked eye, the health of the leaves is used to indicate that the fungal relationship with the orchid is working. If seed is sown in autumn, by springtime, when mature orchids flower, there may be a new crop of tiny seedling leaves around the base of the large mother plants. The appearance of new seedling leaves around mother plants each spring confirms that the fungal relationship is healthy. Seedlings take 3 – 5 years to reach flowering size.
- Use a mix that is at least 50% sand. The bottom of the pot can be pure sand.
- Never use fertilisers (fertilisers can kill fungi).
- Feed the fungus by adding new leaf litter on top of the old litter layer each summer. Chopped up sheoak needles or gum leaf stalks/nuts are recommended.
- Do not repot unless absolutely necessary (eg the tubers come out the bottom of the pot, overcrowding, disease).
Thelymitra nuda cultivated by Les Nesbitt (Slow Multipler)