I’ve been carrying water in to the planter box for the “green wall” in BaanLoiNaam every day over the past few weeks. Now the tallest of the cattails have grown up quite close to the level of the shower head:

You can compare the height of the plants now to the level just a few weeks ago when we planted them. This is somewhere are 1.5 meters of growth over about 3 weeks or an average of about 7cm of growth per day!

It is striking how quickly the water disappears during the day. I installed a small vertical pipe into the sand in the box to allow me to see the water level down inside of it in order to monitor the water level.

If I fill up the planter box with water at night, the water level is barely changed in the morning. But if I fill up the water level to about 30cm in the morning, the water level goes down to zero within 2-3 hours.

I suspect this is due more to transpiration of the water through the cattail leaves than straight evaporation from the plant bed.

Based on how quickly this is growing, I have hope that my idea of a natural grass wall in the bathroom of the floating house is viable since we have seen these plants grow up to 3m in other parts of the land. But at this stage I am mostly worried that the planter box will constrain the roots and restrict growth at some point. At this rate of growth, we should know within a few weeks.