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COIR experiment on lockdown

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Hello all Growers,

Hope you are all well. I did an experiment today and found out something quite interesting. Yes it is a lock down experiment

I am mainly an indoor grower but all my Sarracenia, VFT and Darlingtonia are all outside and watered with rain water. I live in the North West of England.

I grow three hybrids of Nepenthes in a window, a few Drosera binata in a window, a Ping in a window and a hell of a lot of Cephalotus in windows. I went peat free about three years ago. I straight switched coir for peat but always noticed a definite sulk in all my plants on re-potting. I have an eBay (£3) TDS meter and to the 10's they are quite sufficient. I have a eBay Reverse Osmosis (RO) unit I bought  for about £35 and my RO water goes from tap (@360 ppm) to 15-10 ppm depending on the time of year. Well below the magical figure of 50 ppm. No one has died!

I hydrated a whole brick of Coir at the recommended rate using water at 11 ppm (yesterday) from my eBay RO unit. I left it for one day to fully hydrate. After that I put 125 g of coir in a 3.5 inch pot with a disc of clean J-Cloth at the bottom. This is about 250 mL in volume to the brim. I then poured a series of 125 g of water (125mL) over the pot and collected the effluent (what came out the bottom of the pot) over 10 minutes. Of interest was that the volume of the first effluent was only 40 mLs! After that the effluent  matched  just under what I put in. This suggests that the compost was not fully hydrated originally?

Bottom line was that I washed a mass of 125 g of coir with a mass of 125 g of water 10 times and waited 10 minutes to collect the water that passed through that compost. I measured the TDS of each washout. Here are the results:

Wash 1 - 907 ppm

Wash 2 - 600 ppm

Wash 3 - 229 ppm

Wash 4 - 101 ppm

Wash 5 - 50 ppm

Wash 6 - 33 ppm

Wash 7 - 27 ppm

Wash 8 - 25 ppm

Wash 9 -22 ppm

Wash 10 -  21 ppm

Considering I was washing with water at TDS 11 ppm, it took me two washes to get washout less than my tap water! It took five washes to get to the "magic" level of less that 50 ppm much after wash 6 there is no improvement. I may repeat this experiment with water at 0 TDS? Take 11 of the figures.

Bottom line is wash your coir and wash it at least five times. After that it is fine. I have VFTs, Cephs, Sarrs in it but I kind of noticed the water in the trays going up  when I first started using it and I just flushed the pots through a couple of times with rainwater. TDS goes up with passage through peat too (a bit). I suggest the first wash of your coir is using tap water!

Keep safe, and as Jeff and Dallas say...

Happy Growing!

Peace Adam x






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  • 4 weeks later...

This salt thing has always tended to be a problem with coir. If you're lucky, you can get the bricks from someone who rinses it  well before sending it out. I use bricks from Garden Direct and, in the past, this has seemed OK. I have used it as a mix with VFT's and it has been fine. Recently, it has not been fine and I have lost my VFT's, albeit slowly.

I still use the same coir for houseplants and it works OK. Cheeseplants, Aechmia, Aspidistra, Streptocarpus, all good in 100 % coir.

I know that Rob Cantley uses coir for their Nepenthes, they just can't get peat. He tests each batch when it turns up and has been known to refuse a lorryload of coir when he has found it to have salt in it., 

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  • 2 weeks later...

Hello Guys

In the end I hydrated coir using my tap water. I then put it in a cotton tote shopping bag and tied up the handles. I washed it twice with tap water in a sink and squeezed and drained till the TDS more of less matched my tap water. Then repeated with my RO water twice and managed to get the final wash water down to about 20.

This is fine for small amounts but I dread to think what you would do if you needed large quantities.

Don't gross out but I did taste the first wash and it did not taste salty.

Cheers Adam

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Cool. Thanks for sharing your experiements with us.

A few years back,  I was trialling a similar peat-free pathway and my initial tests were all with native Drosera seedlings on the allotment. Originally I loved coir, because of the action and convenience, and the fact I could buy it from the pound store.

After two seasons I purchased a pallet load of reclaimed peat, as harvested from resevoir bottoms (marketed as Moorland Gold). I was not 'in' on RO or TDS measuring devices back then !

Some time after that, I read with great interest on this forum about a grower who uses pure grit for all thier CP's, and tried this with some plants too. Also, I tested a bonsai medium like reddish grit, on a semi-mature seedling Darlingtonia. They grew OK.

After reading the Australian botanist Allen Lowrie, about CP substrate and particle size (personal correspondence, 2013) and further experiments; I became convinced that you can grow most 'truly terrestrial' CPs in pure grit, but only if the particle sizes exhibit both great variation and random distribution volumetrically. Excluding perhaps the terrestrial butterworts.


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