white powder on medium

[kcrane]

I have a number of my orchids on humidity trays and noticed that, over the weekend, that some of them developed a white powder on the medium. Is this white powder mildew and does it mean that I am keeping it too humid, for the lack of ample air movement? Would a fan on low help?

[BigSteve]

Sounds more like residue left by water evaporating , possibly lime.What type of water do you use in the trays?

[kcrane]

It's hard well water. This region(Montana) is notorious for our water, and not in a good way. Should I buy distilled or spring water?

[BigSteve]

If it's just for humidity trays use the well water , keep the good stuff for the orchids.

[Desdinova]

You could also try collecting rainwater.

[Katherine]

I have a number of my orchids on humidity trays and noticed that, over the weekend, that some of them developed a white powder on the medium. Is this white powder mildew and does it mean that I am keeping it too humid, for the lack of ample air movement? Would a fan on low help?

you said you have powder on the medium? Could it be that the flowers blew their pollen? Get yourself a digital temperature/ humidity device. they are very inexpensive and last forever. And, like me, growing on the windowsill, you do need a fan for air movement.

Mildew is not very powdery

[Ron-NY]

With hard water use, flushing the pots of their salt build up should be done on a regular and frequent basis. Not only will one get salt and mineral build up from hard water but also from fertilization. It usually appears crusty and not as powder.

[kcrane]

It isn't pollen because nothing is in flower right now. I'm thinking it is lime or some other minerals residue from misting and the humidity trays, because our water is very heavy with minerals. I'm going to have to get some spring water for watering and just use the well water for the trays.