CARING FOR ORCHIDS DURING AUTUMN - Southern Hemisphere
By Lois Walters - Member Noosa District Orchid & Foliage Society
Everyone grows their orchids under different climatic conditions, but there are a few general guidelines that can be followed during this period.
Check the health of your orchids as often as you can by looking at their leaves. Are they looking strong and green or are there patches of yellow or black on the leaves or are the leaves, particularly on Phalaenopsis, looking shrivelled?
In the case of yellow patches, look under the leaves and down the pseudo bulbs for evidence of mealy bug or boisduval scale. There’s also aphids, mites and snails ready to make a meal of your plants. Treat as necessary with the appropriate Eco oils or insecticide/fungicide.
At this time of the year and with the showers we have been having here on the coast, any black spots could be the start of black rot/collar rot. Treat your entire collection with Phosacid (Yates Anti-rot). Shrivelled Phalaenopsis leaves can indicate that the plant needs a good drink, making sure the bark mix is thoroughly soaked.
Check the root system – rotten roots means too much water. Always have a couple of pairs of secateurs on the go and sterilize them between plants.
Some orchids are still in active growth (the cattleya and oncidium alliances, hard cane dens. and the vandaceous group) whilst others are headed for a winter dormancy period (soft cane dens. and catasetums).
Watering should be cut down to perhaps once or twice a week, depending what rainfall has been received. Remember, more orchids are killed by overwatering than anything else.
Hard cane dendrobiums can be moved under cover from now on as most of them come from monsoon climates where there are wet summers and dry winters.
At this time of the year, water in the morning but do not put water into the emerging flower sheaths of cattleyas or new leads on orchids, especially on Dendrobium speciosums and phalaenopsis. They will rot.
So, what fertilizers should be used during this period?
For those who are time poor and use a slow release fertilizer, an application of an 8-9 months slow release fertilizer (these fertilizers only last six months in our climate) can be given no later than April, but only to the orchids still in active growth.
Should you be using foliar fertilizer, use a low nitrogen fertiliser once a week at a quarter strength. Again, only on those orchids still in active growth.
Continue to stake the new growth on cattleyas otherwise they will grow at a 45 degree angle toward the sunlight and look unsightly should you wish to bench them at Shows.
Keep gravel paths free of weeds and pick up any fallen leaves and bin them. All orchids shed the occasional leaf but over the coming months your soft cane dendrobiums and catasetums will shed most of their leaves. This is natural, so don’t be alarmed. Concrete pathways can be kept free of slime by the application of Alginox.
Some orchids, especially cymbidiiums and soft can dendrobiums can now be moved to sunny positions in order for their flowers to develop. Your phalaenopsis will be waiting for some colder nights to occur before they start initiating their flower spikes.
Hope the above helps you – there will be more information on fertilizers, bactericides, insecticides and pesticides (both natural and biological) in due course.