I have tried to make some self-watering plant boxes where I 3D-print some containers with holes to act as wicks to absorb moisture into a top container with soil. The wicks themselves are packed with soil.
However, some white mold quickly builds up around some of the holes (fairly self-limiting though, it does not get much more than what you see in the attached picture after some days since I first noticed it). I emptied the water and re-cleaned the box, and wiped off the wicks. The existing water had a slight sewage smell to it.
For now, the boxes are directly exposed to light, but will be built in by a wooden enclosure in the "final product".
- Should this be of any concern for the plants growing in the soil? They will be edible greens.
- Can I avoid this, while still using my 3D-printed parts?
Always wet is bad. Ideally you water once a day and the soil mostly dries within 23 hours. You're so close to an ebb and flow style system you should give it a try.
So these self-watering concepts are just wrong then? Loads of videos on them on e.g. YouTube, so I would assume they worked well enough.
How would I change my system into an ebb and flow system? The reason I want a self-watering system is mainly because they are placed in a way that makes it akward to water them and because I want a way to avoid killing the plants when I am away from home which happens often enough.
Maybe the videos are using non organic material as the wick?
An ebb and flow system waters the roots directly. The planting medium is usually some gravel, peet and vermiculite. The peet and vermiculite hold a good amount of water while promoting air flow around the roots.
I'm not good at explaining because I focus on too many little details. Look up ebb and flow systems for some expert advice. They take a little setup but you look 75-80% there already.
The goal is to flood the watering basin so it saturates the medium in the basket, the Ebb, and then shuts off letting the water and nutrients Flow back out.