"Water once a week" kills more houseplants than any pest. Watering frequency belongs to the plant plus its pot, its soil, its light and the season. One pothos drinks every four days on a bright summer windowsill and every two weeks in a dim winter corner.
Stop watering on a schedule. Start watering on a signal.
Gardeners have used the same signal forever: push a finger 2-3 cm into the soil. Dry at that depth means water it. Damp means wait a day or two and check again. That habit prevents the anxious daily splash that suffocates roots, and it prevents the forgotten pot that turns to dust.
What changes how fast soil dries out
Light. More light drives more photosynthesis and moves more water through the plant. A plant in a south-facing window drinks twice as fast as the same plant three metres away.
Pot size and material. Small pots dry fast. Big pots stay wet for weeks, which is why overpotting leads to root rot. Terracotta breathes and dries quicker than plastic or glazed ceramic.
Season. Most houseplants slow down as light drops in autumn. Keep your summer rhythm going into November and you will overwater.
Soil mix. Airy mixes with perlite or bark dry faster than dense, peaty soil. Water sitting on the surface before it soaks in points to compacted mix.
How to water when you do water
Water until the excess runs out of the drainage hole, then empty the saucer after ten minutes. A deep, occasional soak beats a frequent shallow sprinkle, which keeps the top wet enough to invite fungus gnats while the root ball below stays dry.
The signs you are getting it wrong
Yellowing lower leaves, a musty smell and constantly damp soil point to overwatering. Crispy brown tips, drooping that perks up after a drink, and soil pulling away from the pot walls point to underwatering. If you cannot tell which side you are on, a photo settles it.