Aug 162007

Photo © Bulleen Art & Garden

How to keep them thriving indoors in Melbourne!

Please Note: The information below is specific to Cymbidium Orchids. For more detailed notes on the general growing conditions required for all Indoor Plants, check out our ‘Growing Indoor Plants Successfully’ factsheet.

Exotic and incredibly long-lasting blooms in tall elegant spikes, wonderful both indoors and out. Easy to care for and will bloom year after year. Some can get quite large and add an imposing statement in a room, others are smaller with a delicate beauty and with many many colours to choose from there is always one you can’t resist…

Despite popular wisdom, cymbidiums like to be kept evenly moist. Do not allow to dry out between watering, but keep moist but not wet, ensuring that the water freely drains from the pot and doesn’t accumulate at the base. Different temperatures and weather conditions will mean different levels of watering, but the overall aim is too keep them evenly moist, not wet. Consequently in winter you may only need to water once a week, but in summer, every day – depends on the weather conditions – watch for wind – it can dry the potting mix out quickly.

These orchids like light, but avoid direct summer sun. The equivalent of 50% shade cloth light conditions over summer suits nicely. These plants thrive in glasshouses, semi-glassed in verandas and covered or sheltered porches facing east. Cymbidiums can also be grown in a semi-shaded, well protected position in the garden. They thrive under deciduous trees, which provide filtered light in summer, essential to successful orchid growing.

Temperature and humidity
They are happy in Melbourne temperatures, but frost will damage flowering spikes so keep them out of frost. When indoors as they flower, they like a bright spot, but not too warm, try to keep them away from a hot heated area.
They like some humidity so setting your orchids on feet to keep the base free of water, but allowing water to collect underneath, is helpful.

Cymbidiums have three growth phases, the flowering phase, followed by a dormant or resting phase and finally the growth phase. There are several types of fertiliser you can use, slow release prills, and liquid fertiliser, these should be in two types, one for the growth phase with higher Nitrogen, and one for the flowering phase with higher potassium.

When you get your cymbidium it is often in full flower, or starting to flower, despite the abundance of wonderful blooms, it is actually in its resting phase and only needs watering, not feeding. Once flowering has finished add slow release orchid granules to the top of the pot and liquid feed at half strength weekly using flowering fertiliser.

Around November the orchid should finish resting, and should begin to enter its growth phase. Switch to growth liquid fertiliser and feed at half strength weekly – doesn’t hurt so spray the foliage occasionally with this solution. Keep this up all November and December.
In January you want to start the orchid ‘thinking’ about flowering, so change to a flowering liquid fertiliser and use fortnightly (or at half strength weekly). Continue this until flower spikes emerge (commonly early autumn).

Once flower spike has emerged, reduce fertilising by half, but stay using the flowering fertiliser. As the plant begins to flower (spike is staked and up and buds are opening), it starts to enter the rest period and at this point keep watering, but stop fertilising.

Flower spikes are brittle, insert the flowering stake early and tie or clip the flowering spike to the stake as it grows. When flowering is finished, cut the spike off at the base. This is also a good time to trim off any tatty leaves using sharp clean secateurs.

Cymbidiums can alternate between being inside when flowering and outside when finished (or you can keep them inside all the time). If you have them outside you must keep the slugs, snails (use snail bait) and cabbage moth caterpillars away (use Success or Dipel). If you can keep them off the ground this helps with the slug/snail trouble. They can survive heavy frosts, but a heavy frost can damage an emerging flower spoke, so move indoors or protect if this will be a problem.

Advanced plants should be completely re-potted every two to three years. Re-potting should be carried out immediately after flowering, usually from September to November. If the plant requires dividing, it is essential to retain two or three green bulbs to form a new plant. These leafless green bulbs, called back bulbs should be retained. On very old, large and congested plants, the old dead back bulbs may be discarded. Green back bulbs may be used to propagate new plants in spring or early summer. Place some sphagnum moss in the bottom of a clear plastic bag, place the back bulb on top and keep moist until a new shoot emerges in about two to three months. Repotting – use a good quality bark based orchid mix. Cymbidium orchids are epiphytes – they naturally grow on the bark of trees and have their roots exposed. It is essential that air can get to their roots when grown as a potted plant. They need repotting if the bark has broken down so much that there is insufficient air/pore space, or are too congested in the pot. Many orchids will sulk for a while after repotting and may take 6 months or more to initiate flowering.

Use an orchid potting mix and only go up one pot size. Make sure the new pot has a very large drainage hole, or multiple drainage holes. Carefully tip out your orchid, trimming off and dead or damaged roots. Pile a cone of potting mix into the centre of the new pot and very gently spread the roots over the cone, holding the orchid balanced upright while you gently pack more mix over the roots. Leave one day, then water in well.

Spider mites, scale, mealy bugs can be problems. Keep an eye out and treat as needed. Spray with eco-oil or natra-soap and wipe down leaves if problems occur.

If leaving outside, then protect from the depredations of slugs and snails.