I have lately been obsessing over my water quality (again).  This time, I have been concerned that chloramines in my water may cause poor orchid growth and eventual decline.

As I’ve mentioned elsewhere, reverse osmosis water will solve many of your growing problems, since the water from a good RO system is almost as pure as the tropical rain that orchids get in the wild.  I’ve seen firsthand the rapid boost in my plants’ health after switching to RO from San Jose, CA tap water loaded with dissolved minerals.  Many people I’ve informed about the benefits of RO have started off successfully with orchids, or revitalized struggling plants.  So with all of my positive RO experience, why am I having problems now?

Well, when I moved into my current greenhouse space and tremendously expanded my collection of plants, using RO was not as necessary, since the water had low levels of Total Dissolved Solids (TDS).  RO, of course, filters out the dissolved solids in water.  But if your water’s TDS level is low to begin with, RO is less of a requirement.  After having grown paphs for two years in my greenhouse, they seem to do OK.  (I still think they’d get a boost from RO now and then, though).

What set me off on this aquatic chase was a decline in a collection of masdevallias that I acquired.  Masdies definitely prefer high quality water, maybe more so than slippers.  My previous water testing had suggested to me that the water purity at my greenhouse should work for masdies, but after six months, a number of these plants struggled and died.  Maybe it was the summer heat (masdies being cool growers) or something else.  During the summer heat, I tried to water heavily to keep the plants cool, but the plants still suffered.  I had re-potted many of the masdevallias, and in fact, had divided a bunch of the bigger ones, with one division going into one kind of media, and the other division into a different type to determine which media would work best.  Turns out neither of them did, as many plants grown in both kinds of media died at the same rate!

Watching these exquisite orchids struggle and then die was just too much for me.  All of the masdevallias got the same temperature, and the same water…  I can’t do as much about the temperature, but I can definitely control my water quality, so I decided to examine that first.  If it turns out that removing chloramines helps the masdevallias out, then I’m pretty sure the slippers will get some benefit, too.

After scouring the web with a multiple search engine query strategy, I have discovered the following:

1) Little reliable information exists about chloramines and orchids.  (No surprise here.)

2) One published study describes the detrimental effects chloramines have on lettuce roots.  (Food crops always get the limelight.)

3) Chloramines are bad for aquarium fish.  (Save the fishes!)

4) Some home beer brewers and wine makers prefer to get rid of chloramines, claiming that using cleaner water improves the taste of the product.  (I’ll drink to that.)

4) You can get rid of chloramines in multiple ways, either by adding chemicals that break the chloramines down, or by using carbon filtration, which is a feature of almost any reverse osmosis unit.  So if you’ve followed my previous suggestion about getting an RO system, you can rest easy.  (Just make sure you replace your carbon filter periodically).

5) Numerous pot growers address the issue as well, with some saying it will stunt their marijuana plants resulting in less yield (and maybe lower highs?), and others saying that it has no effect whatsoever.  This complete divergence of response is quite typical of the pot-growing community online.  While I have many found pot growers on the web to be extremely clever and, in some cases, deeply knowledgeable, about growing stuff, no one has done a serious controlled study with marijuana and chloramine exposure.  (And I’m not sure whether I’m going to sign up to do one with orchids, either, so don’t get your hopes up!)

OK, so here’s the chemical problem:

Chloramine is a blanket term that describes certain derivatives of ammonia bonded with the chlorine ion rather than the usual hydrogen.  Municipal water providers often use chloramine to disinfect water, having switched from using chlorine gas in the past.  Back in the day, you could rid your water of chlorine (and its putatively bad effects on your plants) by leaving your water to stand overnight: the gas would simply dissipate from the water.

Not so with chloramine, which will linger much longer, maybe inhibit root growth.

On the web, numerous “authorities” claim that chloramines have no negative effect on plant growth.  But no one refers to any controlled experiments to demonstrate this.  Since I have paid-in-full tickets to ride on the RO bandwagon, I think many houseplants — heck, even grass! — would grow better with RO as compared to chloraminated tap water.

So here’s what I’m going to do:

1) Measure the total chlorine content of my greenhouse water to establish a baseline.

2) Run my water through a carbon filter(s) and then measure the total chlorine content again.

3) Water my masdevallias (and all the rest of my orchids!) with the water that passed through the carbon filter.

4) Set aside a control group of plants that will receive water NOT passed through the carbon filter.

5) Record and post results.

OK, this is still not a definitive test, but it should give useful information, especially for those of us concerned about chloramines and orchids.  Stay tuned…

Some Resources and Notes:

1) This is an excellent summary of the chemistry behind chloramines, although geared towards fish keepers:

http://reefkeeping.com/issues/2003-11/rhf/feature/index.php

2) http://www.aoc.gov/aoc/magazine/upload/AoC_magazine_Spring_2011_final_508-compliant_rev.pdf

Orchid growers at the U.S. Botanic Garden in Washington, D.C. found that after the city started using chloramines, orchid root growth began to suffer.  A few people on the web reported similar anecdotal observations.

3) I also spoke with a company (who shall remain unnamed) that sells carbon filters in two grades, “normal” and the more expensive “specially designed for removing chloramines”.  Well, the friendly rep that I talked to said that the water in their area contains chloramines, and they use the “normal” carbon filters, not the “special” ones!  I pestered and pressed the rep for more details, and apparently, it’s kind of a marketing thing (surprise, surprise).  While the “special” filter WILL remove chloramines more effectively than the “normal” filter, the company itself is fine with using the cheaper “normal” ones, and offer the higher-end filter for those folks who demand the peace of mind of having the best quality equipment to clean up their water.  (Actually, I’d probably want that peace of mind if I needed to clean up my water for, say, an aquarium of extremely rare and fragile sea creatures.)