@butlern
Iron is not a problem for the plants. They will love it, iron is a necessary nutrient. Iron will be unsightly, and a problem that will require regular cleaning of good pottery to prevent ugly iron stains on your show pottery. If you find iron build up is quick, less than a year on good ceramics. Find plastic pots the same interior size & shape as the interior of your good show pots. Then just before a show, you can ''slip pot'' your tree from the cheap pot to its clean, identically shaped show pot. Other than unsightly build ups on pots and increasing time and effort required to clean up good pottery, Iron is a non-issue for the health of the plants. Just water away with well water.
Chlorine is not that big a problem. It really does not hurt the plants if it is in concentrations low enough that it is considered safe for humans to drink. If you used to raise tropical fish, and still don't like chlorine because fish taught you that it was a problem, just have a bucket, or tank or whatever container around to let the chlorine gas off into the air for 24 to 48 hours. But seriously for all but the most delicate species of trees, this is not necessary. Heck, they grow in dirt, they can't be that fussy. (humor, this crack about growing in dirt was intended as humor).
Get your well water tested. For about $40 you can get the two tests that really matter. You want the value for Total Alkalinity which is usually written as mg Calcium Carbonate per liter of water. It can also be written as the rough equivalent as ppm Calcium Carbonate. The second test you want is Total dissolved solids. TDS. This is also milligrams per liter or parts per million. The two units are roughly equivalent.
NOTE: pH is NOT the problem, pH is a distraction, and is an independent and largely meaningless measurement when it comes to plant health. If the pH of the water is safe enough for humans to drink it is safe enough for the plants. TOTAL ALKALINITY is a measure of the buffer capacity of the water. This is the critical measurement. If you can only get one measurement the Total Dissolved Solids is somewhat useful as an estimate of total alkalinity. For Illinois, Wisconsin, probably Iowa & Minnesota, the Total Alkalinity will be roughly 75% of the Total Dissolved Solids.
The big problem is the Calcium. It is a necessary nutrient, a macro-nutrient, not a micro-nutrient, but trees that prefer ''acid soils'' will not tolerate excess calcium. Here we are talking about carnivorous plants, Blueberries, azalea, Rhododendrons, to a lesser extent beech, hornbeams, maples and other ''forest edge and understory species''.
Plants secrete buffers from the tips of their roots and root hairs. These buffers will alter the pH of the water film around the root tip to the ideal range for the plant. A study by James Asher, UM, Ann Arbor, showed that the water film surround the root hairs of an orchid (Paph primulinum) measured in situ in Sumatra, the orchid was growing on bare limestone rock, with the roots in contact with the limestone. Rain water running over the limestone was about pH 7.6 or maybe even higher, slightly alkaline. The pH of the water film around the root tips was 5.6 or 5.8, mildly acidic. Later lab studies showed the orchid was actively excreting buffers to modify the pH of the water film around its roots. This is why pH is a trivial problem. The roots will correct the pH by excreting their own buffers. So pH is a trivial problem for plant health. This phenomena has been observer in other groups of plants, conventional wisdom is all plants will do this to some degree or other. The orchid example is one where I knew the principal investigator (J. Asher) and I actually took the time to read the paper. An example from other research would work as well. Most plants will buffer the root tip environment to somewhere between 5.5 and 6.8 pH. Regardless of the pH of the soil.
Now this active excretion of buffers to modify the root environment comes at a metabolic cost to the plant. As long as the amount of buffering required is within the plant's ability to keep up, there is no problem. When it comes to water Total Alkalinity is a measure of the amount of acid needed to neutralize a liter of water expressed as milligrams of calcium carbonate. (by writing it as milligrams calcium carbonate, the issue is not which acid you choose) So Total Alkalinity is a measure of how much acid (or plant excreted buffers) needed to bring the pH of the water film to a level acceptable by the plant. When the Total Alkalinity is high, the plant must excrete more buffers, when the Total Alkalinity is too high for that plant species, the plant won't be able to excrete enough buffers. The pH of the water film will not hit the ideal range for nutrient absorption, and the plant will become weak, show symptoms of nutrient deficiencies and then eventually die, most likely from an opportunistic disease taking advantage of the weakened plant.
So if your water you water your trees with is less than 50 mg/liter as calcium carbonate (roughly 67 ppm total dissolved solids, this is ''pure enough'' water to raise most of the common carnivorous plants. This is excellent water, except it is so low in Calcium and Magnesium you will need to supplement these two macro-nutrients.
Water greater than 50 mg/liter, less than 300 mg/liter as calcium carbonate. Roughly 67 ppm to 400 ppm total dissolved solids. This is water of ''medium hardness'' for horticultural purposes. Good enough for most trees. Azaleas and blueberries would appreciate a dose of rain water at least weekly to flush out some of the accumulating calcium. This will work for the vast majority of trees.
If your well water is over 400 ppm total dissolved solids, or over 300 mg per liter calcium carbonate Total Alkalinity, this would be considered ''hard water'' for horticultural purposes. I know municipal capacity wells in the LaCrosse Wisconsin area, just across the River from Iowa have wells that are producing water that is 1275 mg / liter calcium carbonate Total Alkalinity, with 25% of that alkalinity being magnesium carbonate. This is well water that is roughly 1400 ppm total dissolved solids (the 75% estimate breaks down in this example). These new municipal wells in LaCrosse, created a problem for a certain beer producer. Magnesium at that high a level can cause diarrhea in more sensitive humans. That beer manufacturer had to install reverse osmosis to get the magnesium levels down in its water, and monitor the levels of magnesium in the grains and hops they used to avoid keeping a bad reputation. (
@Adair M the brewery was not the Shiner brewery)
Horticulturally what does greater than 400 ppm mean? Salt tolerant species like Japanese black pine and many junipers, especially shore junipers, will have no problem. Elms should have no problem. Pots will quickly need cleaning. Azalea, blueberry, beeches and hornbeams will always seem to die out on you. Maybe not right away, but in a few years. No amount of fiddling with pH will do anything to help the situation. Only active steps to lower the amount of calcium in the water will work. What solution you choose will depend on the size of your plant collection. The amount of money and time you have for initial set up capital, and your familiarity with technology to set up solutions.
Collect rain water - this is the lowest tech and least capital intensive method for solving a hard water problem. For myself, 10 cheap 3 gallon buckets, scattered around the back yard, these are emptied after every rain event into 2 55 gallon plastic drums. Each bucket might only collect a quarter inch of water, but it adds up. Usually if I start in March, by the beginning of June I have nearly 110 gallons of rain water. Rain is less frequent the rest of the summer, but I use rain water ever other watering for the whole summer. By September my rain barrels will be almost empty, and then our autumn rains set in. The harder your water the less frequently you want to use municipal water between uses of rain water. Remember, in a drought, using municipal or well water, even if it is very hard is better for your trees than dehydration.
There are many articles about plumbing your gutters to collections of 55 gallon drums, and or larger tanks or even underground cisterns if you really want to be elaborate. So saving rain water is a good way to solve the hard water issue.
Reverse Osmosis (RO). From under the sink models to models big enough to generate 1000 gallons a day, how big a system you want depends on how big a plant collection you have. It takes me about 25 gallons to water my bonsai. So a proper capacity reverse osmosis system will need to generate at least one gallon per hour. Reverse osmosis runs water through a semi-porous membrane, that allows water through but not larger ions like Calcium. Remember there is the set up cost, but also the membrane will only be good for a certain amount of time, then it will have to be replaced. Filters need to be installed to the incoming water feed, and the system will waste water, at peak efficiency roughly 2 to 3 gallons of water are sent ''down the drain'' for every gallon of finished, low calcium water. As the filter ages, more goes down the drain. If your well water has a high cost per gallon, the waste from RO is a problem.
Deionizing water - DI - this is where water is run through an ion exchange cartridge. The system is cheap to set up, but the cartridges are a recurring expense. At the lab we used DI- to make our distilled water for tests. Monthly we were replacing cartridges, at $50 each. A good system can give you analytically pure water, but it is expensive to maintain.
Cheap fix - air conditioners and de-humidifyers - If you only have a few plants, water collected from dripping air conditioners and the basement humidifiers is essentially pure water. Low solids. Maybe dust that had accumulated on the air conditioners coils. For a small collection, requiring only a few gallons of water this might be fine.
Purchase water - you can purchase distilled water, if you shop "water services", there are some that will deliver. $ 2 per gallon is what I remember from 10 years ago. Not cheap, but if you only need a gallon or two, grab it when you buy milk.
So those are some options.
Hope this helps.
Leo
