Cymbidium suave

by David Allen and Noe & Rob Smith

Cymbidium suave, one of the three unique Australian Cymbidium species, is possibly the most demanding for an orchid grower to maintain in culture. Some understanding of where and how Cym. suave grows in the wild will help understand its particular requirements. Cymbidium suave is found growing on the east coast of Australia, extending north from southern New South Wales at around latitude 35 to latitude 25 in Queensland, north of Brisbane. The climate range is from moist temperate to moist sub-tropical.

Cym. suave grows in holes and fissures in eucalypt trees, with its root system extending down into rotting heart wood of trees (living or dead). It can also be found growing in cavities in fallen trees, or even in eucalypt fence posts and stumps of felled trees. The root system of established plants may extend down into the heart of trees for many metres. New plants will form from stolon growths along the root system where holes or fissures allow the plantlets to emerge. It is the very particular requirements in regard to its growing conditions which makes this species such a challenge for many growers. Hopefully, by providing the views and methods of several growers who successfully grow Cym. suave, others will be able to maintain this unique and beautiful species as well.

Most growers agree that the specific conditions necessary for the species to grow in nature need to be replicated as closely as possible in culture if the plants are to survive for any length of time. Unlike many Cymbidium species and most hybrids, which only require a potting medium to provide a suitable degree of moisture retention and the addition of fertilizers, etcetera, to provide nutrients and an acceptable pH level, Cym. suave seems to have more specific requirements. Growing the plants in rotting eucalypt heart wood as found in nature is generally reported as producing better results than the use of a typical Cymbidium medium.

With pH levels being recorded at between 4 and 4.5 in nature and in tests on this medium in culture, it may well be that pH is a critical factor in the successful maintenance of Cym. suave. While the pH level of other forms of potting media could be adjusted to replicate those found in rotting eucalypt heart wood, it may well be that Cym. suave also obtains required nutrients from the process of decomposition and those nutrients, in a particular balance as produced in the process, may be critical to the plants' growth.

Many growers also believe that the conditions in nature provide a degree of insulation to the plants' root system and a control of moisture levels necessary to the plants health. As a result, many growers either grow Cym. suave in lengths of eucalypt with rotting hearts, or find sections of suitable hollow logs and fill them with rotting heart wood and plant Cym. suave in those. Other containers such as lengths of clay sewerage pipes have also been used with reports of good results when filled with rotting eucalypt heart wood.

Some growers believe that the extra depth provided by length of pipe (or logs) provides the sort of root run Cym. suave prefers. Larger, well-established plants will also grow happily in the same medium when potted in large "normal" Cymbidium pots, but not for very many years before needing to be repotted. As Cym. suave resents being disturbed, most growers try to avoid repotting unless absolutely necessary.

Our (Noe and Rob) own experiences with Cym. suave over some fifteen years has seen us grow (or attempt to grow) this species in a variety of mixes and containers. Mixes have ranged from traditional Cymbidium mixes made up of pine bark with various other materials added such as canunda shell, marble chips, rice hulls or coir in combinations, to similar mixes with proportions of eucalypt chips, or rotting eucalypt added and rotting eucalypt alone. Certainly the use of rotting eucalypt alone, or in fairly high proportions within a mix has provided the best results under our climatic and cultural conditions.

Although our plants of Cym. suave grow in the same orchid houses as our other Cymbidiums and are watered at the same rate and frequency, they receive less fertilizer and what they do receive is always a balanced type, rather than a high nitrogen type as commonly used for Cymbidiums for at least part of the year. We do not add slow-release type fertilizers to the mix for Cym. suave and only fertilize at about one-quarter strength or weaker. Tests on rotting eucalypt heart wood in our pots of vigorously growing plants of Cym. suave have given pH results of around 4.5 and we try to keep the pH at that level as the plants seem to be happy with it.

We wouldn't be surprised if the pH factor isn't more important than the actual medium and perhaps someone reading this article who has done tests with Cym. suave will be able to share their experiences with us all. To date we haven't done any tests along these lines, mainly because we don't want to kill any plants. Cym. suave can be very difficult to re-establish once the plants begin to go backwards, especially if they loose their root systems.

Rob & Noe Smith

David Allen describes his experiences growing Cym. suave as follows: I decided to grow a couple of plants of Cym. suave about five years ago and have found the plants to be quite hardy; they grow, flower and thrive under the conditions I have provided for them. After a little research, I found that the natural habitat of Cym. suave covers a wide region from southern NSW (almost to the Victorian border) to Cairns in northern Queensland. While this species can be found growing on a number of hosts, it seems to establish and grow best when its roots can penetrate rotting heartwood in live eucalypt trees, where it will form large clumps.

Cymbidium suave produces a large number of roots which will travel long distances into the rotting wood. In order to reproduce this sort of environment under culture, I have planted my Cym. suave in old hollow eucalypt logs. I use a potting mix of 50% composted pine bark and 50% rotten eucalypt heartwood; to every litre of this mix I add one cup of charcoal.

The plants are grown in my main growing shade house, under 50% shade cloth, along with the rest of my Cymbidium collection. They are placed in the brightest area of the house. I was told by an experienced Cym. suave grower that these plants like a lower pH than other Cymbidiums, somewhere in the 4.5 to 5 range. To achieve this level I water the plants once a week (in the growing season, but not in winter) with a solution of water and lemon juice at the rate 10ml. of lemon juice per litre of water. The plants are fertilised with crushed Dynamic Lifter pellets at the rate of one table spoon per plant at the beginning of spring and summer.

The plants seem to be very hardy once established, but I make sure they get some protection against extreme weather conditions, such as frost in winter and hot northerly winds in summer. Given these conditions and culture, the plants reward with excellent floral displays in late spring. I'm not quite sure what I will do once they out grow their existing logs; probably go forest hunting for some larger logs and pot them on, if that's the right word?!

David Allen