Dendrobium canaliculatum has a widespread reputation as being a difficult orchid to grow. Otherwise excellent orchid growers are often unable to keep this species alive for more than a couple of years. Others have them survive, but the plants never really thrive. These problems under cultivation are equally true here in the tropics, even though they grow wild in their countless thousands just a few kilometres from our bush houses.
To be honest I dread writing this page about orchid cultivation. One thing I have learnt is that many different growers have different approaches, sometimes wildly different, that can all work well. We probably all know someone who does everything wrong – they plant their florist's Phal-Den hybrid in the ground next to the Hydrangeas – and yet the damn orchid thrives! Actually, that person may be me and what works for me may be orchid poison to others. All I can provide is a guide to what (and by my reasoning why) I do to achieve moderate success with Tea Tree Orchids. I believe this of value, but please ensure you interpret for your own situation.
In its wild habitat the Tea Tree Orchid is a tough little plant and many are small things or clumps of mostly leafless back bulbs with one or two leading shoots. However this is not how they need to be. Plants growing wild in higher rainfall areas and under good cultivation do grow into thick clumps with dozens of fully leafed bulbs. I have seen wild plants growing on Swamp Box in the Macalister Ranges (north of Cairns) - a relatively high rainfall climate. Some clumps would be 50cm in diameter, with the majority of bulbs fully leafed. At first glance, I thought I was seeing clumps of Cymbidium canaliculatum! Now a plant will throw one to three spikes per leafed bulb – imagine the display these clumps must put out in spring!
Growth can be equally good under cultivation. Dendrobium canaliculatum is actually not all that different to other orchids to cultivate, so long as one considers several core requirements. As a believer that everyone’s growing situation and successful growing style is different – the key is to adapt Dendrobium canalculatum’s core requirements to your own conditions, style and preferences.
There are three key requirements to success with Dendrobium canaliculatum:
I believe if you can maintain the above, whatever else you do, Tea Tree Orchids will grow in your orchid collections There are however a few more details and tips to keep in mind to keep them to their absolute best. Below is a discussion of key factors media, water, temperature, humidity, light, food, pests and diseases as they relate to cultivation of this species.
Apologies in advance for not having a table of contents to help you navigate this page, as it is a little long.
Tea Tree Orchids have an absolute requirement for lots of air and oxygen exchange to their roots and an absence of decomposing or anaerobic (sour or stale ) media. Many growers mistake these needs for a requirement to regularly dry out completely or be cultivated relatively dry. Whilst reduced watering can help to manage some problems, overwatering per se is rarely the root cause of the issues with this species cultivation.
Grow too dry and the plants will never perform to their full potential. To the contrary when one gets the media and growing conditions right it is almost impossible to overwater. My plants never completely dry out and I have even grown Dendrobium canaliculatum successfully semi-hydroponically*.
Do not be afraid to overpot if using airy, inorganic media
Growers can avoid many problems with Dendrobium canaliculatum by avoiding, or being very selective, about using organic media and mounts. I recommend primarily or entirely inorganic media. Various types of gravel, LECA (Lightweight Expended Clay Aggregate) and perlite are all excellent. For mounting, plastic mesh tubes filled with the aforementioned media, upturned unglazed ceramic pots or plain (no bark), weathered hardwood or cork is best.
Success in bark or other organic media is possible however it is always a riskier technique that requires more attention as the media begins to decompose. The key is to repot to fresh media very regularly and to grow the plants relatively dry so as to slow the process of decomposition of the media. Good quality hard, slow decomposing bark is essential. The moment the media starts to break down, your Tea Tree Orchid is in trouble. The same applies for growing mounted on branches of paperbark or tea-tree. It generally works great at first, but once the bark gets to a certain stage of decomposition, your orchid may die quite quickly. A live tree renewing its bark is different to a dead piece in the greenhouse.
With all potted Tea Tree Orchids, it serves well to be rather ruthless with the roots when repotting. A mass of decomposing old roots will kill the plant as easily as a musty bark compost. Many roots on old bulbs will be spent after a season or two. Cut them off and blast the rest with a high pressure hose to remove any remaining organic matter. If repotting an orchid from an organic media, remove what you can at first, than in a couple of months pull the plant out of its new pot and remove any remaining old roots. Some growers of Cooktown Orchids (Dendrobium bigibbum) and Cymbidium canaliculatum work on a similar basis, even removing all roots from plants prior to each growing season.
I do not like to keep many back-bulbs on my plants either – one or two behind the last leafed bulb is enough. As an aside, back-bulbs strike very easily if placed on damp pure perlite.
|Leafless backbulbs (some woody and shrivelled), about 5 months after being placed in a pot of damp perlite. Every one sprouted – some are already onto their second new growth||Single, rootless and badly damaged bulb encouraged to grow by placing in pure damp perlite. This plant has subsequently made two additional leads from the new growth shown here.|
In ideal conditions (never too cold) I believe a relatively moisture retentive, airy, inorganic media will give the best results with the least problems. I am currently using pure, coarse (about 5mm-8mm) perlite in pots with excellent results (in the dry tropics). Coarser media works well too however I find small cockroaches and slaters are able to live in media that is too coarse (and subsequently chew the new roots). It is worth understanding that the volume of air spaces within a mix is maximised in media with well-graded (evenly sized) particles and is not related to the size of the particles themselves. Shallow pots are excellent, or fill normal pots to a third or half with clean coarse gravel and top with perlite (or similar).
I don't generally use clear pots, but here is one showing the root growth of Dendrobium canaliculatum var. canaliculatum grown in pure perlite
I have also grown Dendrobium canaliculatum in pure LECA (semi-hydroponically and normally) and gravel with success. If growing in marginal conditions (e.g. Sydney with limited or no heating) I would try growing on bare upturned unglazed ceramic pots or sawn, aged hardwood slaps – particularly if the plants were not under a solid cover (to keep winter rain off). The plants will unlikely grow quite as well as in pots, but there is more margin for error to deal with cool and damp conditions as the plants can be dried out very quickly. In between these conditions, I would look at potting (or mounting on mesh tubes of) LECA and/or gravel – possibly with the addition of some hard wearing bark or charcoal. Avoid the lava gravel, smoother gravel (e.g. road metal) has less potential to trap organic matter. It is also possible to add a thin layer of perlite to the top of a plant in gravel or LECA to slightly improve moisture retention a fraction – I prefer the layers to mixing the two media as keeping the two fractions separate maximises the air spaces in the media.
Dendrobium canaliculatum var. tattonianum growing in pure LECA. Bulbs have elongated with good growing conditions even though grown under high light levels
Whenever you bring in a new plant to your collection be aware that a couple of growing seasons will be required for the orchid to fully adapt to your growing media and conditions. Orchid roots develop differently according to the media and cultural conditions they form under. If you grow in gravel, only the new roots formed in this media will be best adapted to thrive in the gravel. Place a mounted plant into pure perlite, and all of the existing roots will be next to useless and soon die off. Only newly grown roots will be adapted to thrive in the new media and environment within it. For this reason, I find seedlings, small divisions of 2-3 bulbs or even single back-bulbs adapt quicker to my bush house than larger plants. Expect the most difficulties growing Tea Tree Orchids in the first and second years under your cultivation as they either adapt, or fail, under your particular conditions and growing style. Also, some clones are just naturally stronger in cultivation than others. Seedlings originating from flasks are a better bet for strong plants in cultivation than divisions of wild-sourced plants.
Not a Dendrobium canaliculatum, but a hybrid (Dendrobium Memoria Lloyd Bradford or Dendrobium speciosum x canaliculatum) demonstrating the adaption of the orchid to it's new growing environment as described above. The red arrow shows the three increasing growths from the nursery that propagated it. The blue arrow shows the first, rather poor, growth made in my bush house under new cultural conditions (constant watering) and media (pure perlite). The pink arrow shows the first of the subsequent strong growths after the orchid adapted to my growing style. Picture to the right shows the root system at repotting just before the last growth - to show what the roots are doing
If growing in inorganic media as recommended, do not be afraid to overpot. My experience has been that with quality media that has extensive air spaces and is unable to break down, plants benefit from the more stable conditions of a larger mass of media, and also from spreading their roots more extensively with more media and air between each individual root. I am well aware that most growers consider the opposite (i.e. underpotting) as beneficial or even essential to growing good Dendrobiums.
*As an aside, I would recommend every serious orchid grower visit Ray Barkalow’s website on semi-hydroponic orchid culture (HERE) and read the Semi-Hydroponics and Free Information (general information) sections – even if you have no interest in every trying semi-hydroponics. What the evidence from Ray’s semi-hydroponic technique is brilliant for is correcting many misconceptions about growing orchids and watering in particular – which will help all growers grow better orchids.
I read much about Dendrobium canaliculatum noting that in the wild it grows with heavy rainfalls in the summer (wet season) and next to no rainfall for the rest of the year (dry season). This is true for most areas it grows but is also misleading as a guide to cultivation. Firstly, for much of the dry season, wild plants get good dew-fall in the early hours of the morning – on the branches they grow this little bit of dew means their roots are well saturated for a couple of hours nearly every morning of the year. Secondly, how a plant grows in the wild is never a perfect guide to how to grow them with the most success in cultivation.
Tea Tree Orchids grown in airy, inorganic media and warm conditions tolerate, and indeed thrive, with lots of water. In the wild in the wet season, they often go weeks with near constant rain – it is warm and the roots have plenty of oxygen. In winter, it almost never rains, and can get surprisingly cold (sub 10 degree celcius minimums for weeks on end). The plants get a good dewfall in the early hours of many mornings (often saturating their roots) however they completely dry soon after sun-up. Spring (flowering season) is the driest in both rainfall and dewfall, however plants still receive intermittent dew-falls and are better watered than a casual observer may surmise.
Humidity mist just after sunrise in late September. Just north of Coen (Cape York Peninsula). The mist and dew completely lifts within an hour of sunrise and the days are hot and dry
There is no humidity mist this morning on Cape York in the peak of the dry season. The roads are dusty, the grass is brown and crackles underfoot and much of the country has already been burnt. However most mornings dew falls in the thin forest where Dendrobium canaliculatum grows. Photo to the right shows a Melaleuca viridiflora leaf just after sunrise. Photo to the left shows a Tea Tree Orchid on the same tree. This orchid has for its purposes been fully watered this morning, as it is nearly ever morning. Most never notice as within an hour of first light the moisture has evaporated and the days are hot, dry and sunny. The dead bulbs are primarily due to previous fires (it is only 1.5 metres from the ground).
In my bush house, I water at least three times a week, 52 weeks a year. I have plants of Dendrobium canaliculatum that have grown that way for over ten years. They have never completely dried out and perform well. I do have to adapt new plants to these conditions as most grow them drier. This is usually quite easy (especially for seedlings, small divisions and in the growing season) but occasionally plants suffer initial set-backs. In the longer term, plants adapted to frequent watering are easier to manage, as it is much simpler to ensure plenty of water at all times than to constantly judge the best line between overwatering and desiccation. It also means that my plants do not suffer during our constant, wet season rainy periods (note that this would be an issue in a colder climate regardless of growing media).
Regular watering flushes decomposing matter and metabolites out of the pots and brings fresh, oxygenated water to the roots. In addition to the automated watering, I like to heavily flush each pot by handheld hose about once a month. To grow these orchids well, focus on getting the media and growing conditions right and the rest should full into place. They grow ok with the traditional wet-dry cycle, but do not be afraid to grow them with lots of water as well.
|This little back-bulb propagation has been grown wetter than ideal (note the algae and moss) but it demonstrates how well moisture is tolerated with correct media (pure perlite in this case) and otherwise good growing conditions. Also note the healthy green roots||Small plants in a seedling flat in pure perlite. Again, note the algae due to constant moisture|
But of course the above is subject to a reality check and that is the fact that no-one can maintain perfect growing conditions all the time. If your conditions get too cold (e.g. days that don’t rise above 20 degrees celsius and/or leaves that don’t dry out completely by mid-morning) it is a sound strategy to cut right back on the watering. It is not necessarily the best for the plants’ growth and performance, but they will be at less risk of problems than being wet when cold. Cold and wet orchids risk rot setting in from even previously healthy roots and leaves dropping from fungal problems. It is in these climates that I would recommend mounting, as it is much quicker to dry out a mounted plant if required (and hence give them some water in winter) than one in a pot.
Some readers may be more familiar with Tolumnia (Equitant Oncidiums) which are also regarded by many as difficult to grow and needing to dry out between waterings. I grow mine identically to my Dendrobium canaliculatum however at the higher level of shade (70% shadecloth). Note again the moss and algae
Again, be aware that an orchid that has always grown on a dry mount will not simply take off once it is moved to a nice moist pot. Indeed, it may be killed if the change is at the wrong time. Best to move small divisions of a few leafed bulbs ideally just as they are starting to make new growths. That way, new roots will be formed that are adapted to the new conditions. The plant may make poorer growths at first until it has fully adapted and established to the new growth media. Alternatively, a plant can sometimes be placed on a mount in a pot, and encouraged to grow down into the media with new growths over time (see image below).
Tea Tree Orchid encouraged to take up a potted lifestyle by first growing on a mount in a pot
Many references to growing Dendrobiums state definitively the need to 'rest plants' for a number of months during the cooler season of the year. This rest generally consists of withholding all fertiliser and almost all water so that the plants stay dormant. The rest is said to be important to achieving flowering in the following season.
My experience with Dendrobium canaliculatum (as well as Dendrobium bigibbum and the other tropical Dendrobiums that I grow) is that a forced rest is not required at all to achieve good flowering. The plants naturally slow their growth in the cooler months but I continue to water and fertilise three times per week as I do year round. A forced rest may be a useful technique in marginal (cool) climates to reduce the risk of problems related to the cold. It may or may not be essential for good flowering in soft-cane (nobile-type) Dendrobiums. However I say with confidence it is not needed to achieve good culture and flowering with Dendrobium canaliculatum.
Dendrobium canaliculatum is a tropical plant. Its southern limit of distribution is right on the Tropic of Capricorn. There is no getting around that both in the wild and in cultivation this is a plant that loves lots of heat.
Yet they can also tolerate more cold than most growers give credit for if the general cultural rules for this species are followed. They naturally grow much further south (some 800km further) than Dendrobium bigibbum, which along with its countless mostly bigibbum hybrids (Phal-dens) are the most popular cultivated Dendrobiums around the world. I know of wild colonies of plants growing in highland areas that experience occasional scattered frosts in the winter (though not on the plants themselves). Night-time minimums of 6-8 degrees celsius are not uncommon in winter through much of its wild range. However even at their limits, wild Dendrobium canaliculatum almost never sees a day that doesn’t get above 20 degrees celsius. Similarly, it is rare that a wild plant would not dry out completely by mid-morning through the cooler half of the year. They can take some cold, but not for too long, and only for very short periods if they are wet. Summer minimums, when these orchids grow the strongest, are typically 24-28 degrees celsius and humid.
Tea Tree Orchids can be cultivated anywhere Phal-Dens grow successfully. They can certainly be cultivated without any heating or protection as far south as Brisbane. I have seen them grow well tied to live trees in Brisbane and near Gympie. With special care they can be cultivated as far south as parts of Sydney without heating, although a solid roof to protect them from winter rain is almost essential at this latitude. Any heating or additional protection through the winter will reduce problems and produce better plants. By Melbourne, some sort of greenhouse (solar or heated) is e essential for at least a few months of the year in order to keep them alive. When conditions are colder, even in North Queensland, plants will still drop a few leaves, particularly leaves that have experienced damage (e.g. from insects) or were not strongly formed in the growth phase. The plants hold these damaged leaves in the warm months, however abort them as conditions cool.
Dendrobium canaliculatum cultivated on Jacaranda trees near Gympie (Southeast Queensland). This area has relatively warm and humid summers, however winters are quite cool, often wet or misty in the mornings, and grounds frosts occur throughout the winter. The Tea Tree Orchids do not grow as strongly as in the tropics, however do survive and flower (these have been on the trees for many years).
At the other extreme, being tropical plants, one would expect the Tea Tree Orchid to be highly tolerant of hot conditions. This is true, with a couple of caveats. Firstly, if it is hot in the tropics, it is always humid and often there is good air movement in the thin forests that this species grows. Dendrobium canaliculatum will desiccate under very hot and dry conditions much like any other orchid. Also, their roots can swelter at the edges of plastic pots that heat up in the sun in warm conditions. I even find here in the tropics where it grows naturally, it is hardier in the shoulder seasons (September to November and March to May) than the peak of summer. It probably benefits from a little extra shade in the brightest months of the year. Secondly, very hot days (e.g. 40 degrees celsius +) are actually rarer in the coastal tropics than further south due to humidity build-up capping temperatures. So give your Tea Tree Orchids plenty of heat within limits, and like any orchid combine this with lots of water and air movement.
Tea Tree Orchids appreciate good humidity however they also tolerate fairly low humidity very well. They normal orchid growing rules apply.
Warm to hot temperatures with very high humidity are not appreciated when air flow is poor. For those with closed-in greenhouses a fan running over the plants for a least the warmest hours of the day is a good investment. Very high humidity and little air movement makes it difficult for plants to transpire - that is evaporate moisture through their leaves in order to draw water through their roots. In warm, very humid conditions the plants will try to grow vigorously, however with inadequate transpiration are unable to draw enough water and dissolved nutrients through their roots to support the growth. This leads to nutrient deficient, spindly new growths that are prone to fungal collapse and insect attack. Low transpiration also means the leaves do not cool through evaporation, and even Dendrobium canaliculatum leaves can get too hot and burn or swelter.
Low humidity is tolerated well where the plants are otherwise well watered and healthy. This is a species that is adapted to daytime periods of low humidity particularly in spring, albeit with reasonably regularly dew-fall for a couple of hours of the early morning.
Given the chance to acclimate, Tea Tree Orchids grow and flower well in a broad range of lighting conditions, from about 70% to 0% shade. I do see wild Tea Tree Orchids continuing for years on the top branches of long dead Melaleuca viridiflora without a hint of shade at any time of the day. They can be adapted to, and grown in full sun under cultivation as well (never put a shaded orchid straight out into full sun). However they do better with some shade. I prefer 50% shade here in the tropics and believe they are a little stronger under the higher light and flowering is maximised. They still grow and flower surprisingly well under 70% shadecloth and indeed some plants grow very sturdy under the greater shade. If your plants are not performing or going backwards under high light levels, try taking them to about 70% shade (similar light levels to species such as Dendrobium tetragonum prefers) and you may get a better response. This is particularly the case in summer. In the wild, the thin forests produce masses of new leaves with the first rains in late November and December, and shade levels increase considerably for the summer months. However much shadier than about 70% and growths will be spindly and weak and flowers are unlikely.
Adequate light stimulates strong plants and lots of flowers
|Dendrobium canaliculatum var. tattonianum ‘Highland Bruise'||Dendrobium canaliculatum var. tattonianum ‘Keeper #1’|
I don’t believe that Dendrobium canaliculatum is different to other orchids in regard to its fertiliser requirements. Any general and complete nutrition program that works well on your other orchids is likely to be fine. Perhaps the only key message is that plants grown in inorganic media (as I recommend) are completely dependent on the fertiliser for all their major nutrients and trace elements. It is important to use complete, well-balanced formulation. Whilst some references state that high-nitrogen fertilisers should be given to this species in the growing season, I favour low-nitrogen, high potassium fertiliser year-round.
My plants receive a weak complete inorganic fertiliser (1/4-1/3 recommended strength Peter's Excel CalMag 12-6-20) through automated watering three mornings per week and maybe twice a year a pellet or two of chicken manure based organic fertiliser in the pot. If in any doubt feed weaker (more dilute) as newly growing roots can burn with too much fertiliser. Better to grow them a fraction slower than to halt their root development. They probably benefit from all the other tricks (seaweed, silicon, etc.) but it is certainly not essential to growing quality plants. I also like to flush pots heavily by hose every couple of weeks or so. This has several benefits: 1. It flushes accumulated fertiliser salts; 2. It flushes out organic metabolites excreted by functioning roots; and 3. It removes decomposing organic matter that would otherwise contribute to the development of anaerobic conditions within the media.
One thing to avoid with fertilising for this species is large quantities of organic fertilisers that may decompose in the root zone and create issues. This is particularly the case in the cooler months.
Pests and Diseases
Healthy Tea Tree Orchids are relatively hardy and some reasonably common problems with my other orchids (scale, spider mite, thrips) rarely trouble them.
They are particularly attractive to chewing pests however, with new growths and roots vulnerable to attack by grasshoppers, cockroaches, dendrobium beetles, caterpillars and even slaters. My bush house is open on one side so these critters find their way in and sometimes cause great damage. Sometimes it appears they all take a liking to a particular plant. It is heartbreaking to see a succession of new growths on the one plant (usually a preferred clone!) mown to nothing. My future bush house will be fully enclosed to reduce these pests.
Be particularly aware of rats and mice. Rodents will chew on many orchids but in my mixed collection they chow down on Dendrobium canaliculatum (and to a lessor extent its hybrids) ahead of everything else. Indeed in my collection they never attack Dendrobium speciosum or its hybrids, not Dendrobium bigibbum and its hybrids but will strip row after row of Dendrobium canaliculatum. They especially like new growths and seedlings - I recently lost over 80% of a newly deflasked line-bred Dendrobium canaliculatum in two nights to rodents - heart breaking stuff.
The below Dendrobium canaliculatum shows the typical damage caused by rats or mice. Unfortunately Dendrobium canaliculatum is particularly favoured by rodents and in my bush house at least, they focus on this species almost exclusively.
This bulbs of this wild Tea Tree Orchid have been chewed by something - so it is not just in the bush house! The locals prior to European settlement of Australia apparently roasted and ate the pseudobulbs of Dendrobium canaliculatum so they must be quite tasty.
Thrips do also attack developing flower buds, causing individual flowers to be aborted.
Individual flower buds aborting after being damaged by thrips.
Fungal problems and extensive leaf drop are an issue in cool, damp and/or still conditions. Solid covers are a good investment if growing these orchids in areas with cool and wet wintery conditions. However it is usual to still experience some leaf drop as conditions cool - particularly on leaves that have been damaged through insect attack or other means. Fungus is able to enter the leaf through these weak spots once the plant's defence mechanisms are weakened in cool weather.
Dropped Dendrobium canaliculatum leaf in winter. The leaf had suffered some insect damage (Dark spots) when it was formed. This caused no issue during the warmer months, but following a period of cool and damp conditions in winter fungus finally invading the leaf causing the plant to abort it.
Plants will also often drop some leaves in the lead up to flowering, presumably as they remobilise nutrients held in the leaves to the development of flower spikes. Some clones seem to be more susceptible to leaf drop (and no, it doesn’t appear to be related to how tropical the climate they originate from). Furthermore, Dendrobium canaliculatum, its hybrids and other 'Tea Tree Orchids' do seem to be rather sensitive to sprays that cause photo-toxic effects (e.g. sulphur, white oils). Certainly, I have experienced leaf drop issues from these sprays on the Tea Tree Orchid group where other groups of Dendrobiums (e.g. the Dendrocoryne group - speciosum, etc.) are completely unaflicted.
If you are unlucky and fungal issues turn systemic (invade some pseudo bulbs) the best approach if you are quick is to remove the affected bulbs along with few of the healthy ones adjoining them. Clean up all old roots, dry out the bulbs for a few days, and repot in new, clean media. Only if the issue is noticed early will this work, as plants can die very quickly with fungal systemic diseases.
Fungicides may be useful, however other than wettable sulphur (which I cautiously spray 2-3 times a year for mite control – more for my other species) I do not use them. For one, I do not suffer cool conditions for too long. In general, I attempt to focus on air movement, good media and plant management to keep fungal attack at bay – though like most growers my growing area is not optimal. I believe it is best to work on the assumption that fungal pathogens are always present and will always attack if a plant is provided with the conditions that favour them.
Dendrobium canaliculatum var. canaliculatum ‘Empire of the Sun’. Top quality Tea Tree Orchids are easier to grow than most appreciate provided a few key requirements are met