A self-watering insert sits inside a Grovie cache pot, under the nursery pot, and holds a reservoir of water separate from the soil above it. Here's what's actually going on inside one.
The reservoir
The insert's base is a shallow tray that holds the water store, sized to the 4 in and 6 in cache pots it fits. There's no separate tank or tubing — just the tray itself.
The wick
A wick strip runs from the base of the tray up through a cutout in the ledge the nursery pot rests on. It draws water upward by capillary action, carrying it from the reservoir to the nursery pot resting above.
The ledge
The nursery pot rests on a raised ledge a short distance above the reservoir floor, keeping its drainage holes clear of standing water.
Refilling
How often the reservoir needs topping up depends on the plant, the room and the season, so Grovie doesn't put a schedule on it. Lift the nursery pot out to check the tray, and refill when it's low.