Why Are Gardeners Told Not To Leave A Plant In Water, Empty Saucers. But Self Watering Plant Systems Have Soggy Soil In The Bottom

Question

of their pots. not needed

Answer 1

Self-watering pots do not work for every plant. For example, they should not be used for succulents or other plants that need to dry out between waterings. But plants that need evenly moist soil, but not saturated, may benefit from a self-watering container.

The difference between a self-watering pot and a regular pot and saucer with water is that the self-watering pot has a wicking system that regulates the uptake of water. Saucers filled with water can allow the soil to absorb all the water at once, essentially saturating the roots and leading to root rot.

Here is more: https://www.gardeningknowhow.com/special/containers/what-are-self-watering-pots.htm