Self-watering pots with a wick and a window

A self-watering pot is two containers: a plastic inner pot with drainage holes, sitting in a reservoir. A cotton wick runs from the reservoir up into the soil. That is the whole machine, and it works on one principle: capillary action moves water from wet to dry, and stops when the two are in balance.

Why the roots do not rot

The fear with anything that keeps soil moist is root rot. Rot needs waterlogged soil, where the air spaces between particles are full of water and the roots suffocate. A wick cannot do that. It only moves water as fast as the soil above it dries, so the soil stays damp but never saturated, and the drainage holes let any excess fall back into the reservoir instead of pooling around the roots. The plant drinks from the bottom for a week or more, and the top of the soil stays dry, which is also why fungus gnats lose interest.

The window

The reason we picked this design over the closed ones: a clear strip on the reservoir shows the water level. You fill it when the window is empty, not on a schedule and not by poking a finger in the soil. Watering becomes a thing you notice rather than a thing you remember.

Good for, not for

• Good for: pothos, philodendron, peace lily, ferns, herbs on a kitchen sill, and anyone who travels. Plants that like even moisture and hate the wet-dry swing of top watering.
• Not for: succulents, cacti, snake plants. They want the soil to dry completely, and a wick will not let it. Keep those in a plain terracotta pot.

Two honest notes from the reviews

The six-inch size reads smaller than the number suggests; it suits a plant that is currently in a four- or five-inch nursery pot. And the base twists on with some effort. Once it is on, it stays on.