Sources for the general advice on this page: UConn Home and Garden Education Center, Houseplant Watering Recommendations (homegarden.cahnr.uconn.edu), checked 2026-10-13; University of Vermont Extension, Houseplant Care During the Winter Months (uvm.edu/extension), checked 2026-10-13. Details of how PotPal calculates its estimate are PotPal's own approach and are labelled as such.
Do not water on a calendar
UConn extension advises against a fixed schedule, because needs vary with species, light, temperature, humidity and growth stage. Its test: push a finger about an inch into the potting mix. If it feels dry, water thoroughly.
What changes how fast soil dries
| Factor | Effect, per extension guidance |
|---|---|
| Heat and heat sources | Plants dry faster in heat and near heat sources, which are common indoors in winter |
| Growth stage | Plants use less water when growing slowly, and more during active growth |
| Pot material | Unglazed clay dries faster than plastic or glazed pots |
| Pot size | Too small needs more frequent watering. Oversized pots hold extra moisture and encourage overwatering |
| Leaves | Plants with thick, waxy or few leaves need less water |
Winter
University of Vermont Extension advises that plants grow more slowly in winter, so wait until the mix is really dry. It suggests pushing a chopstick into the soil: if soil sticks to it, skip watering.
How to water
UConn recommends watering deeply, because frequent light watering encourages shallow roots. Water until it drains from the holes, and empty the saucer within about an hour.
How PotPal builds its estimate
PotPal's own approach: start from a seasonal baseline for the species, adjust for light, pot material and size, location, temperature, humidity and soil medium, fine-tune from your feedback, and keep the result inside a safe range for that species. It shows the result as a range, and the plant's detail page has a Why this interval view that shows the steps. Temperature and humidity come from the season by default, or from local weather if you switch on weather calibration. These factors are PotPal's engineering estimates, not published horticultural constants, so use them as a starting point and let the soil check decide.