Odonts Potting Mix

[jjurlina]

On his Mathers video Jim is using essentially sphagnum moss for growing odonts. Is this a standard mix used by other?

[MrCym]

No, people just use what is locally available! Remember, NZ has the finest Sphagnum Moss in the world (Mile High Moss!)so look to Hokitika...... However, we grow super Odonts at Colomborquideas in basically a mix of bark particle sizes. I'm sure someone in The Netherlands is growing them very successfully in a peat-based medium!

[richardb]

I saw this video too. It is all to do with what works for individual environments. The Mathers huge climate controlled automated greenhouses are very different from the average amateur set-ups. For me, it is all about drainage and how long one wishes roots to have direct access/contact with water, and that is affected by the surrounding temperature and humidity. I have tried many different mixes over the years and settled eventually on a pure bark mix. In fact I have used Melcourt medium bark for many years. That said, I am very particular about what gets into my greenhouses so before bark touches my plants it is seived through a 1/4 inch seive to get rid of fines (which I can use for seedlings later), washed twice, then soaked for at least 24 hours before being washed twice again. Contrary to some growers' ideas I then dry the bark and pot while dry before leaving for about a week then give a jolly good soaking/draining.
Works best for me.

[jjurlina]

Thx for the replies.
I have always used NZ sourced radiata pine bark for orchids, varying the grade as required.This gives good drainage and water retention, but may be quite acidic, given this most commercial orchid bark is sieved and treated lime to address this. Not sure if there is an opitimul pH for orchids. From a cost pertspective little else is added to the bark mixes, many decades back there was a local supplier who made his own bark formula for orchids and he added polystyrene chips to improve aeration. I used this when I was growing cymbidiums and it was a great mix.
He used to supply it in a 200L sack for large users, sadly he sold his business and the orchid mix disappeared.
There is now a fern fibre from a native tree fern that is being promoted as the best potting material for orchids. This takes me back to reading of the use of osmunda fern fibre, comes with great references but some growers have said that it retains nutrients and the pots need regular nwith plain water to prevent build up of salts. I dont use artifical fertlisers so this may not be a problem for me.

[Gary S]

Interesting Richard, have you measured the pH level of the bark before you use it. Many growers here will sieve the bark like you do to get rid of the fines and then soak it. In general the raw bark here (both Aus and NZ origin) is alkaline out of the bag, and a lot of growers will add a mix of Urea, Epsom Salts and Iron Sulphate (in measured proportions to the amount of bark) to the bark as it soaks to bring the pH level up. It is soaked for a couple of days then removed and laid out on plastic sheets to dry out before using.

[jjurlina]

Interesting Gary, so you are saying that an alkaline pH is not the best option? I suspect hast this may arise iff the bark is treated with lime to raise the pH ?

[Gary S]

I think in general the correct pH level for growing orchids is 6.0 to 6.5.
I dug out the formula that was devised many years ago to treat bark, normally sourced from Pinus radiata both here and in NZ.
For a 50 liter bag of bark the following is mixed and added to the bark to soak in water for 48 hours, it is then washed and dried out before use.
130 grams (4.6 ozs) Urea
350 grams (12.5 ozs) Dolomite or Micro Fine Lime
25 grams (0.8 ozs) Potassium Sulphate or Sulphate of Potash
35 grams (1.25 ozs) Ferris Sulphate or Sulphate of Iron

Adjust the ratios to suit the bag size.

Many growers here still use this to treat bark. Note, Orchiata used to treat the bark with Dolomite, but since the company changed hands a few years ago, I don't know if this is still the case. Most bark from here is aged, hammer milled, graded and bagged without any treatment.

[jjurlina]

Again very usefull info, I can see the relevance of all the additions with the exception of the ferrous sulphate.
Most Orchidata bark made here is exported, the only way to access it is to belong to an orchid society, not a big deal. but some societies are now looking to change to an alternative local supplier, exact reasons not known, maybe the volume that must be purchased. I undxerstand that Orchidata bark is left outtside in the weather for some time, this may see leaching of some of the bark components, good or bad who knows.

[Gary S]

Basically the Urea is there to add a Nitrogen component to the bark for the next 3 to 6 months in a pot and the other 3 components work together to adjust the pH of the bark into the range required, again studies show the pH remains in range in the bark in the pot for a good 6 months or more, depending on how often one fertilizes and what type of fertilizer is used. Normally it is not needed to fertilize the orchid in this treated bark mix till after 6 months or more in the pot.

Kiwi Orchid Bark from Taranaki NZ, is not composted at all and is very hard and lasts a long time in the pot, it definitely benefits from this treatment.

Since Orchiata was sold to Dalton's, the bag size has dropped and the price has risen quite a lot here in Aus, I also detect a difference in quality.

The Kiwi Orchid bark comes in a 50 liter bag as against the 35 liter Orchiata bag and is the same price here in Aus as the Orchiata ($45.00 AUD retail per single bag) - so the Kiwi bark is a much cheaper proposition and in my view now a better product. I use both and find the Kiwi bark lasts 3 times as long in the pot. The Orchiata bark seems to be softer now - probably composted for a longer time before being bagged.

[jjurlina]

Kiwi Bark was the alternative brand that I was referring to. Of course Orchidata/Daltons would argue that the quality has not changed but a few users here would agree witth you. The difference in price will always be a big factor in the decision on which brand to purchase. Orchidata has developed a loyal following in the markets they sell into and from what I can gather thier export quantities are of a profitable size which is why they dont bother with NZ sales.