5. Get watering and feeding on a system, not on memory
Containers live or die on water. A 15-litre pot in full sun in July can use two litres a day, and a single missed day at the wrong moment splits tomatoes, bolts lettuce and makes basil run to seed. Nothing else on this list goes wrong as fast.
Water in the early morning where you can, or the evening if mornings are impossible. Midday watering in hot sun wastes most of it to evaporation and scorches wet leaves. Water the compost, not the plant, and water until it runs from the drainage holes — a splash on the surface wets the top inch and encourages shallow roots that then cook in the first heatwave.
Check by weight and touch rather than by schedule. Push a finger two inches into the compost: damp means wait, dry means water. Lifting a pot slightly tells you more than looking at it. In peak summer most balcony pots need water daily; in spring and autumn, twice a week is often plenty, and overwatering in cool weather kills as many plants as drought does in hot weather.
For holidays or an unreliable memory, self-watering containers with a reservoir are worth the extra cost — they hold several days of water and even out the swings that cause splitting and bolting. A cheap alternative is a plastic bottle with two pinholes in the cap, inverted into the compost. Grouping pots together also helps, because they shade each other’s sides and raise humidity.
Feeding starts about six weeks after planting, when the compost’s built-in nutrition runs out. Use a balanced liquid feed fortnightly for leafy crops and herbs, and switch to a high-potassium tomato feed weekly once tomatoes, peppers, chillies or strawberries begin to flower. Potassium is what builds fruit; too much nitrogen gives you a magnificent green plant carrying four tomatoes. Follow the dilution on the bottle exactly, since doubling the dose scorches roots rather than doubling growth.