We're all familiar with compost. In order for things to grow, there can't be debri/blocks above the compost. The idea is to use jars of water and connect pipes to it to make the air humid. Only works if it's inside a closed space of blocks. So a little green house. If you want to make your house a little more lively you could use that as a way to give water to your plants. Through the power of steam into the air. No more having to worry about placing your protector up in the sky to prevent trolls from placing blocks above your protecting space.