Tap water on mounted orchids
 

What is the view on using tap water for mounted plants? It would be much easier for me to use tap water on a timer for my orchids mounted on cork but I am wondering what your views are on this. I know that hard tap water causes a build up of salts in plants in pots but would this be the same for mounted plants? It is difficult to keep my water butt topped up with rainwater especially if I go on holiday and if I can use tap water on a timer and fertilise seperatley it would make life much easier. Also the pump I have in the water butt doesnt have enough pressure to get all the way around the circuit now that I have so many of my orchids mounted each with individual drip feeds.

Depends on your local water and what you're growing, but I mostly use tap water and haven't noticed mounted plants being significantly more sensitive in this regard than potted. Probably the opposite, actually, because it's easier to wash off salt deposits as they develop. Do you have access to a water quality analysis?

Thanks Nat. I dont have water quality analysis but i believe it is hard and we use a water softener in the house. However I dont think it is outrageously hard. Perhaps if I use tap water most of the time on the mounted ones and just give them a rinse occaisionally with rainwater - what do you think?

All sorts Dendrobiums, laelia, cattleya, msdevallia, brassavolas

You can buy a meter to test for "total dissolved solids", which will give you an idea of how hard the water is. They are pretty inexpensive--$20 USD and up I believe.

Water softeners use salt as a part of the ion exchange process. That salt is a potential risk to your plants (as a broad generalization, orchids and many other plants are intolerant of sodium and are more likely to be tolerant of calcium and magnesium). Can you take water for your plants from a tap before it reaches the water softener?

I echo gnathaniel's other comments (which is easy because we live in the same town and are on the same public water supply).

Added later: Assuming a large number of plants, you may want to consider a reverse osmosis unit for your orchid water.

I dont use the softened water in the orchid house. The garden tap and orchid house water are straight from the mains. I dont mind getting a RO unit but how would that solve my pressure problems and would it constantly top up with fresh water if I am on holiday?

A good RO unit isn't that expensive, and eliminates Cal buildup, however you would want to add fertiliser to that at a very low dose. I use about 25 ppm Nitrogen on everything, every watering, and like you I have a wide range of orchids on mounts. Basically, almost everything that can go on a mount does, and the ones that can't, - well, I'm working on it!
First Rays has good fertiliser advice, and a cracking RO unit for sale.

Do you have to switch a RO unit on and off or can it just fill up a water butt like a toilet cistern and switch off when full?