More plants die drowned than dried out, and that's no accident: watering is the action you repeat most often, so it's also the one where mistakes come back most often. Here you're going to learn to read a pot rather than a calendar, to water thoroughly without ever letting the roots soak, then to automate the whole thing with a properly tuned drip system. By the end of this step, you'll know exactly when to water your tomatoes, chillies and peppers, why, and how to keep that rhythm even on the days you're not around.
Overwatering, the beginner's number one enemy
Roots need air as much as they need water. A permanently waterlogged substrate drives the oxygen out of the pores in the growing medium: starved of air, the roots turn brown, stop absorbing, and the whole plant stalls. The trap is that this shutdown looks exactly like a lack of water: the leaves grow heavy, droop, and sometimes yellow from the bottom up. The natural reflex, watering a little more "just to be sure", then makes everything worse: this is precisely the mechanism that kills the most beginner plants, far more than the drought everyone worries about.
There is, however, a simple test to tell thirst from excess water. Water your plant thoroughly, then watch:
It was thirst
If it perks back up within the hour or two that follow, it really was thirst.
It's excess water
If the substrate stays visibly damp and the foliage doesn't recover, or even keeps yellowing from the bottom up, it's excess water, and watering more will only dig the problem deeper.
Also look at the time of day before drawing a conclusion: a plant that wilts a little in the afternoon heat, with foliage still green and standing well in the morning, is simply reacting to the heat, not to a lack of water.
As for figures, the agronomic reference gives a clear benchmark: water again before you've used up 40 to 50 % of the available water in the substrate, never after. Past that threshold, the plant is already suffering, silently at first, then visibly. In practice, nobody measures that percentage of available water at home: the practical proxy is the weight of the pot, which comes close to that threshold without being strictly equal to it (we'll detail the method just below).
Collateral effect. A minor side effect of overwatering: fungus gnats, those little black flies that lay their eggs in a substrate that stays damp at the surface. Less surface moisture, fewer fungus gnats.
🌶️🍅 For chilli or tomato seedlings, water from below rather than from above: set the pot for a few minutes in a shallow dish of water, then let it drain. The whole root ball takes up moisture without soaking the surface, which discourages fungus gnats and limits damping off, the disease that flattens young plants at substrate level within a few days.
