posted 11 years ago
Sitting in standing water, the roots will rot. Better to get some cotton rope/string and thread that through the drainage holes (I use a bent piece of wire as a "needle" and thread the string all the way to the surface) so it hangs down in the water below, with the pot propped above the water (use stones, cross-pieces of scrap wood, piece of fencing, whatever). Water will wick up 7 inches from a cotton rope/string but the soil seems able to stay moist a little bit higher than that. I've been doing this for a few years now and am always surprised at how well the moisture spreads through the soil in the pot from the wicks so they stay evenly moist.
Two things to watch out for - mosquitoes (good fish food) and the cotton rotting and falling apart so that it no longer wicks. Some cottons are far better than others at the whole rotting thing. You can even use strips of old jeans or t-shirts for the wick.
In the wicking beds, they put in a substrate like wood chips that will pull the water upwards but not tempt the roots to grow down into the water where they'll rot. I find that many plants grow their roots down into the water anyway and not all of them rot, some are far more water-resistant than others, but it might help to keep the water levels more or less constant so they "know" where the water/rotting level is.