How often should you water that?
Forget vague "water when the top inch is dry" advice. Get exact day intervals by plant, pot, light, and season — computed from RHS 2025 baselines.
Baseline watering intervals.
| Plant | Summer (days) | Winter (days) | Light need |
|---|---|---|---|
| Fiddle-leaf fig | 8 | 14 | bright indirect |
| Monstera | 7 | 12 | bright indirect |
| Pothos | 9 | 14 | medium |
| ZZ plant | 18 | 28 | low to medium |
| Snake plant | 21 | 35 | low to medium |
| Peace lily | 6 | 10 | medium |
| Philodendron | 8 | 13 | medium |
| Rubber plant | 9 | 15 | bright indirect |
| Spider plant | 8 | 13 | medium |
| Moth orchid | 7 | 11 | medium |
| Calathea orbifolia | 5 | 9 | medium |
| Chinese money plant | 7 | 12 | medium |
| Hoya carnosa | 12 | 21 | bright indirect |
| Anthurium | 6 | 10 | medium |
| Bird of paradise | 7 | 14 | bright indirect |
How to adjust for your setup.
- Pot materialTerracotta dries 20–30% faster than plastic or glazed ceramic. Reduce days accordingly.
- Pot sizePots under 4 in dry ~25% faster. Pots over 10 in dry ~20% slower.
- HumidityIf your room sits under 40% (heated/AC winter rooms), reduce intervals by 15%.
- LightPlants in lower light than their preference water slower — up to 30% longer intervals.
- Still check the soilThis is a baseline, not scripture. Stick a finger 1–2 in into the soil before watering.
How the math works
Start: RHS species baseline. The Royal Horticultural Society publishes a default watering interval per species in temperate indoor conditions. For Snake Plant: 14-21 days. For Pothos: 7-9 days. For Fiddle Leaf Fig: 8-10 days. We use the midpoint of each range as the starting number.
Light multiplier. Brighter light increases transpiration. AoB Plants 2024 measurements show roughly 1.4-1.8x water uptake in bright indirect vs medium light. We apply a 0.7x to 1.4x multiplier across light tiers. Plants in low light dry out 30% slower; plants in bright light dry out 40% faster.
Season multiplier. Winter dormancy cuts metabolic water use 30-50%. We use a 0.6x multiplier in winter for tropical houseplants and 0.7x for desert-origin succulents. Hard rule we've learned the expensive way: never run a single year-round schedule.
What we exclude: humidity (it shifts intervals by less than a day in most homes — see the humidity calculator), plant size relative to pot (a root-bound plant dries 25% faster), and air movement from fans or open windows. Add 10-15% buffer if you keep a fan on the plant.
Worked examples
- 2L Pothos in a north-facing Sydney apartment, summer: RHS baseline 8 days, low-light multiplier 0.7x = 11-12 days between thorough waterings. If you set a calendar reminder for "every 2 weeks" you're ~15% under-watered, which Pothos tolerates fine.
- 5L Snake Plant in a west-facing London room, winter: RHS baseline 17 days, bright-light 1.4x but winter 0.6x = ~14 days. Counterintuitive: more light AND winter cancel out, so the schedule is close to baseline. Most schedule errors here come from people watering on summer cadence in winter.
- Fiddle Leaf Fig in a Toronto south window, summer: RHS baseline 9 days, bright-light 1.4x = ~6-7 days. Watch the leaves for early droop as your local cue. Fiddle leaves go from firm to slightly soft about 24h before serious wilt.
FAQ.
Why is watering frequency different in winter?
Most houseplants enter a semi-dormant state in winter due to reduced light and lower temperatures. Metabolism slows, so water uptake drops 30-50%. Over-watering in winter is the single biggest cause of root rot — more than over-watering itself, the seasonal mismatch is what kills plants. The schedule values shown here are split by summer / winter precisely for this reason.
Should I bottom-water or top-water?
Bottom-watering (soaking the pot in a tray for 15-20 min) reduces salt buildup and encourages deeper roots. Top-water once a month to flush minerals. Either is fine; what matters more is the interval (drying out between waterings) than the delivery method. African Violets and other fuzzy-leaf plants prefer bottom-watering because wet leaves spot.
How do I know my plant is over-watered?
Yellow lower leaves, soggy soil three or more days after watering, mushy stems at the base, and a sour smell from the soil all indicate over-watering. Let the soil dry 70-80% between waterings as a default. The wet-finger or weight method (see our watering methodology guide) is more reliable than calendar-based scheduling.
Does pot size really change the schedule that much?
Yes. A 6 inch pot holds roughly half the water of a 10 inch pot for the same plant, so it dries out in about half the time. The intervals shown here assume a standard well-draining potting mix in a pot with drainage holes. Decorative pots without drainage need ~30% less water and longer intervals because the bottom layer of soil stays saturated.
What about humidity — does that change watering frequency?
Yes, but less than people expect. High humidity (60%+) slows transpiration so a plant uses ~10-20% less water through its leaves. But the soil still dries from evaporation through the pot surface. Net effect on watering frequency: maybe a one-day stretch on a 10-day cycle. See the houseplant humidity calculator for plant-specific humidity targets.
How were these intervals calculated?
We started with the Royal Horticultural Society 2025 baseline watering frequencies for each species, then adjusted for two variables: (1) light level, because brighter light increases transpiration roughly 1.4-1.8x; (2) season, because winter dormancy reduces water uptake by 30-50% as documented in AoB Plants 2024. The numbers reflect a typical 6-8 inch pot in a temperate climate (Sydney, Melbourne, London, Toronto). For arid or tropical climates, expect ±30% drift.