The most common watering mistake
The most common houseplant mistake is watering a little bit every few days. This approach keeps the surface of the soil damp while the deeper soil — where the roots actually live — stays dry or gets inconsistently wet. It's a pattern that leads to shallow root systems and stressed plants.
Most houseplants do better with deep, infrequent watering: water thoroughly until it drains from the bottom of the pot, then wait until the soil has partially or fully dried before watering again.
How to water thoroughly
Water slowly and evenly across the surface of the soil until you see water draining from the drainage hole at the bottom of the pot. This ensures that the entire root zone gets wet, not just the top layer. Allow the excess to drain completely — don't let your pot sit in standing water.
For very dry or hydrophobic soil (soil that's been dry for a long time often repels water), you may need to water twice in quick succession, or bottom water by placing the pot in a basin of water and letting the soil absorb moisture from below.
How to know when to water
Rather than watering on a fixed schedule, check the soil. Push your finger an inch or two into the soil — for most tropical foliage plants, water when this depth feels dry. For succulents and cacti, wait until the soil is dry all the way through.
You can also lift the pot. A dry pot is noticeably lighter than a wet one. With practice, this becomes a quick and reliable method.
Light changes everything
A plant in bright light will dry out faster than the same plant in low light. The same plant in summer will dry out faster than in winter, when growth slows. Watering frequency should shift with the seasons and with changes in light. There's no single schedule that works year-round.
Bottom watering
Bottom watering — placing a pot in a shallow basin of water and letting the plant absorb what it needs from below — is a useful technique for plants that prefer not to have wet foliage or for very dry soil that repels water from the top. Leave the pot in the water for 20–30 minutes, then let it drain before returning it to its spot.