Tomatoes grow brilliantly in pots on a sunny balcony or windowsill — but they’re hungrier and thirstier than herbs, so they need a bit more attention. Nail five things — a big enough pot, lots of sun, consistent watering, regular feeding, and some support — and you’ll be picking your own tomatoes all season. Here’s how to care for them.
Start with a big enough pot
This is the most common beginner mistake: too small a pot. Tomatoes have big root systems and drink a lot, so a small pot dries out and stresses the plant. Use at least a 20–30 litre pot (around 30 cm wide and deep) per plant, with drainage holes. Fill it with a good-quality potting mix, not heavy garden soil. Cherry and dwarf varieties are by far the easiest in containers.
Sun: as much as you can give
Tomatoes are sun-worshippers. They want 6–8 hours of direct sunlight a day to produce well. A bright, south-facing balcony or windowsill is ideal. In too little light you’ll get a leggy plant with few flowers and fewer fruit.
Watering: consistency is everything
More than anything, tomatoes want steady, even moisture. Potted tomatoes dry out fast — often needing water once or even twice a day in peak summer. Check daily: push a finger into the soil and water deeply whenever the top few centimetres are dry, until it drains from the bottom.
Feeding: tomatoes are hungry
Tomatoes need far more feeding than herbs. Once the plant starts flowering, feed it every 1–2 weeks with a feed higher in potassium (a “tomato feed,” or organic options like compost tea and diluted seaweed). Regular feeding is the difference between a few tomatoes and a heavy crop.
Support and pruning
Most tomato plants get tall and heavy with fruit, so give them support early — a stake, a cage, or ties to a balcony rail — before they flop over.
If you’re growing a tall “indeterminate” variety, pinch out the side shoots (the small stems that appear in the “armpit” between the main stem and a leaf branch). This channels energy into fruit instead of extra foliage. Compact “determinate” and dwarf types don’t need this — just let them bush out.
Common problems, quickly solved
- Flowers but no fruit → poor pollination (shake the plant) or temperatures that are too hot or too cold for fruit to set.
- Black patch on the bottom of the fruit → blossom-end rot from uneven watering. Water more consistently.
- Yellowing leaves → often overwatering or hunger. (See our guide on why plant leaves turn yellow.)
- Curling leaves in heat → usually the plant conserving water on a hot day; give afternoon shade and keep watering steady.
Harvesting
Pick tomatoes when they’re fully coloured and give slightly to a gentle squeeze. Harvest regularly — the more you pick, the more the plant produces. Near the end of the season, any green tomatoes will happily ripen indoors on a windowsill.
Want a plant that tells you exactly what to do each day — when to water, feed, and watch for problems, adapted to your local weather? That’s exactly what UrbanLeaf is built for. And if you’re growing herbs too, don’t miss our basil care guide. 🍅