Problem. The first version asked me to open the app, find the plant and press a button after every watering. I stopped after a week. That is the same adoption problem I see in CRMs: if logging costs more than the work, nobody logs.
Built. A 25 mm NFC sticker on each pot. Tapping it logs the watering, with an undo in case it was the wrong pot, and a warning if the plant was watered too recently. A photo of a new plant fills in the species, the pot size (the sticker is the ruler), the light and a watering plan. Outdoor plants skip a watering when it already rained. One reminder a day, and a plant list for whoever waters while we are away.
A model choice with a real cost. Before adding more users I tested the photo reading on my seven plants. The larger model named six of seven correctly and the smaller one named four, and one of its misses called a rose a sunflower. A reading costs about one cent with the larger model and a wrong species costs the plant, so I kept the larger one and put a daily cap per person instead.
Result. Seven plants on stickers since September 2026, used by the household.