Plant Watering Calculator

Commonly around 10 to 25% of the pot's soil volume per watering, enough to wet the whole root ball and produce a little runoff. The exact share depends on the plant and the medium.

It confirms the whole root ball is wetted rather than just the surface, and it flushes accumulated fertiliser salts. Watering that never produces runoff lets salts build up until they burn the roots.

No. Shallow frequent watering keeps roots near the surface where they dry out fastest. Thorough watering less often drives roots deeper and makes the plant more resilient.

Test the soil rather than the calendar — a finger a few centimetres in, or the weight of the pot, both work better than a schedule. Requirements change enormously between summer and winter.

Considerably. Terracotta is porous and dries far faster than glazed ceramic or plastic, so the same plant in the same conditions needs watering more often in a clay pot.

Because pots narrow towards the base, so the cylinder implied by the rim diameter overstates the soil inside. The reduction keeps the water quantity proportionate to the actual root zone.

Both cause wilting, which is why they are confused. Over-watered soil is wet and the roots are dark and soft; under-watered soil is dry and pulls away from the pot edge.

Yes, without exception for most plants. A decorative pot without them should hold an inner pot that does, so the plant is never standing in water.

Standing the pot in water and letting it wick up. It wets the root ball evenly and avoids compacting the surface, though it does not flush salts — so an occasional top water is still needed.

Chlorine dissipates if water is left standing, and hard water leaves mineral deposits over time. Sensitive plants such as carnivorous species genuinely need rain or distilled water.

Substantially less. Lower light and cooler temperatures slow growth, so the same plant may need a third of its summer water. Winter over-watering is the most common houseplant killer.

It raises humidity only momentarily and does little for most plants. A humidity tray or grouping plants together works far better if dry air is the actual problem.