Flushing with tap water

[marcoeverard]

Hi. I am brand new to semi hydro and have done what I was warned not to and connverted almost everything to semi-hydro. My orchids have been struggling and seem to be either too dry or too wet so I thought I didnt have much to lose. The Phrags are already showing good root growth after a few weeks so at least they like it. I am wondering if it is ok to fluh the pots regularly with tap water which is a little on te hard side and then flush with feed and rainwater every 4th or 5th time? I don't have enough rainwater to use just for regular flushing so either I need gto use tap water or get a RO unit and i would rather not at least until I see how they are doing? Sorry if this has been asked before but I couldn't find an answer I love the idea of S/H as I am not always at the orchid house property and being able to leave them occaisonally with a reservoir of water will suit my lifestyle. Any suggestions on what feed to use would be great too. I am in the UK and have been using rainmix but wonder if something else would be better if they are not being fed at every watering.

[Ray]

Marco.

The first thing you must do is find out what’s in your tap water. I suspect the delivering agency can tell you, if they don’t have it posted online.

If your water is very hard - you’ll get mineral heavy deposits on pots and pans, on the tap itself, and eventually, even around the drainage holes of the S/H pots - that might be a problem, long term.

If that’s the case, Rain Mix is probably not the best fertilizer, as it has more calcium in it, and an excess can impede the uptake of other nutrients.

Don’t worry about that too much - pretty much any water-soluble fertilizer will do.

[marcoeverard]

Ray this is probably a silly question but if all the old roots die off during transition then why don't you cut them off or at least thin them out to lessen decaying roots in the new pot?

[Ray]

Originally Posted by marcoeverard

Ray this is probably a silly question but if all the old roots die off during transition then why don't you cut them off or at least thin them out to lessen decaying roots in the new pot?

I don’t remove them because their functioning is not an “all or nothing” thing. The “suboptimal” roots still function to some degree for a while, helping support the plant while it gets established.

About the only time I might remove good roots is if the pot is just packed with them, but that’s more to be able to more easily spread them in the new medium.

[marcoeverard]

Ok thanks Ray. I thought that might be the case and I did have to trim some of the roots on a couple of them to fit them in the pot. Otherwise they would have been very little leca in the pot as well.

[marcoeverard]

Just wondering if flushing out thoroughly with tap water and then topping up the reservoir with rain water and fertilizer solution is a good option

[Ray]

Originally Posted by marcoeverard

Just wondering if flushing out thoroughly with tap water and then topping up the reservoir with rain water and fertilizer solution is a good option

Flushing saturates the LECA with whatever is in the water, precluding absorption of the fertilizer solution, so that water has to begin evaporating before the fertilizer will be drawn upward into the root system. (OK, there will be a little diffusion, but that takes longer and would dilute the fertilizer even more.)

If your watering technique is to rapidly fill the pot to the top with dilute fertilizer solution, you flush, water, and refresh the reservoir all at once.

[estación seca]

My water is probably much more mineral-laden and alkaline than yours. Just water them profusely (flush) every 1-2 days and they should do well.

[marcoeverard]

I got a water report but I have no idea what it means see attached. Does anyone understand this and if so how would it affect my feeding regime?

[estación seca]

Originally Posted by marcoeverard

I got a water report but I have no idea what it means see attached. Does anyone understand this and if so how would it affect my feeding regime?

For a gardener the pertinent parts of a water report are the pH and the information dealing with how much total mineral is dissolved in the water. Almost all the total mineral dissolved in the water consists of calcium and magnesium salts. These two elements are essential nutrients to plants, so gardeners need to ensure the plants get them from the water, or from fertilizing.

A municipal water supply in the US is highly unlikely to have significant amounts of any toxic substances because they test so frequently.

Your pH is shown as 7.16-7.64. This is tolerable for most orchids. A lot of people recommend pH in the range 5.5-6.5 for orchids. When mixed with various fertilizers the pH of your water might come down (that is, become more acidic.) If you wanted, after mixing your desired fertilizer, you could measure the pH of your solution, and adjust it to the pH you desire. pH is very important because the elements needed by plants are more readily available at a pH somewhat lower than neutral, which is 7.0. Even with lots of calcium in my water, the pH of 8.0-8.5 makes most of that unavailable to plants unless I use acid to bring the pH of my water down. (I do that.) If you search online for "plant mineral absorption pH chart" you will find a standard chart to show this.

Some suppliers report total mineral content in milligrams of dried precipitate. Yours reports the electrical conductivity (EC.) Electrical conductivity is a measure of the number of electrical charges on charged ions in a solution. In most water systems this is mostly calcium and magnesium. These are important elements to plants, so they do matter quite a bit. The other metal ions listed on the first page contribute to this, but they are in very small amounts. If you know the EC, and the other things present in your water, you can calculate how much combined calcium and magnesium are in there, but you can't calculate exactly how much calcium and magnesium.

However, reports always show the the maximum tolerable amount of substances in the samples. In your report this is in the column labeled PCV (relaxed.) For EC the standard is 2,500 uS/cm. In other words, if there were enough calcium and magnesium to reach an EC of 2,500, the water would be unacceptable. At that level mineral deposits would accumulate on everything, and plug pipes relatively quickly.

The report shows the EC in your water is minimum 680.000, maximum 1100.00, with a mean of 859.583. That means there is substantial amount of calcium and magnesium in your water, 35% on average of the maximum tolerable.

So, if I were in your position, I would use any fertilizer with trace nutrients, and adjust the concentration based on the amount of nitrogen I wanted to give. If I used MSU fertilizer I would choose the one for well or tap water, not the one for pure water. I would use neither calcium nor magnesium supplements because there is plenty of both in the water. I would measure the pH of my fertilizer solution and adjust it to a value of about 6.5.

You can measure pH with paper test strips, liquid test kits sold at aquarium or swimming pool stores, or pH meters. A good meter is very expensive. I use an aquarium test kit because I already have it for my aquaria. I use vinegar to adjust my pH, but I don't grow in clay pots. I've been told using vinegar to adjust pH leads to rapid growth of algae on clay pots, which breaks them down to crumbles. People growing in clay pots can adjust with something called N-pHuric acid, bought at an agricultural supply store. A local hydroponics shop will also have products to lower or raise pH.