Milk bottle waterer

Recently we went away for a few weeks.  I was worried that my carnivorous plants would dry out and die.  These are swamp plants, and need constant water, and I didn't know what to do.  

My carnivorous plants are growing in trays that normally hold a low level of water, and I try to keep the water at a constant (yet low) level.  I filled the trays to the top with water, but knew that it would not last until we returned.  I was worried that things would dry out and die before we returned.  

The day before we left I had an idea.  

I got some empty milk bottles and filled them with water.  I punched two holes in each of them, one slightly higher than the other.  These milk bottles should act as a waterer, and fill up the tray when water dropped below the higher hole.  I expected this to work in the same way as the waterer that I use for my chickens.  This sounded good in theory and I hoped that it would work.  

I put a milk bottle waterer in each of my trays except for one.  I would have put one in each, except I didn't have enough bottles.  Having one without the waterer would be good for comparison.  

When we left, everything looked great.  I hoped that this would work.  

Milk Bottle Waterer and trays filled 

Milk Bottle Holiday Waterers

When we returned home, all of the trays with milk bottles still had water in them, the tray without a bottle was dry.  This means they worked!

I expected air to enter the bottles through their highest hole when the water level dropped, and for them to be largely filled with air when I returned home, but this was not what happened.  

As you can see from the pictures below, water certainly left the bottles, but no air entered them.  The bottles were sucked in and crushed.  The water level of the trays is at the highest hole.  I put the higher hole at this level as it is the level I usually keep the water at.  

Bottle waterer crushed

Milk Bottle Holiday Waterers

Strangely enough, there were some tiny water beetles and other aquatic insects swimming inside some of the bottles.  Presumably they live in my trays and had entered through the holes in the milk bottles.  

Next year when I take leave if we go anywhere I will have to remember to do this again.  Even though I don't understand why the bottles were crushed, it was cheap, it worked well, and it kept my carnivorous plants watered for over two weeks.