30 studies, every one cited on the page where it is used. A pot is not a small garden. It is a sealed vessel with a permanently saturated layer at the bottom, a root system that cannot go looking for water, and a temperature that swings further than the ground ever does. Five things make it different from a bed, and every beginner mistake is one of those five being forgotten. The one that surprises people most: drainage is a property of the mix, not of the pot. The same compost holds the same saturated depth whether you put it in a tall pot or a shallow bowl — which is why your seed trays rot and your deep pots are fine, and why it was never about how you water. This is a field manual to the vessel, with the study behind every number. What is in it - The perched water table, explained properly — what it is, why its height is set by the medium, and why a short wide pot is proportionally far wetter than a tall one holding exactly the same compost. - The gravel question, answered honestly. The famous myth-bust says a gravel layer lifts the water table into the roots. A 2025 experiment found a coarse layer usually *reduced* water retention. The book prints both, names the mechanism, and gives you the recommendation that holds either way. - The single biggest lever there is: size. A meta-analysis of 65 studies found that doubling pot volume increases plant biomass by 43% — and that the loss in a small pot comes mainly from a fall in *photosynthesis per unit leaf area*. A root-restricted plant is not just smaller; it is running its leaves slower. - The 1 gram per litre rule, from the same work — and the fact that about 65% of published experiments break it, which is to say most of the science is done in pots that are too small, and so is most gardening. - Colour and heat. Substrate in a black plastic pot runs about 17 °C above ambient air, with recorded peaks of 56 °C. Measured side by side: 36 °C in a white container against 50.3 °C in a black one. Roots are far less heat-tolerant than leaves, and the symptom — wilting in sun despite moist compost — gets read as underwatering nearly every time. - What is actually in a potting mix, what each component does to air and water, why garden soil fails in a pot, how to mix your own, and what to do when compost turns hydrophobic and water runs straight down the sides. - Watering as a method rather than a habit — how much, how to tell, leaching, sub-irrigation, and what to do when you are away. - Feeding, EC and lock-out — including why a great many "deficiencies" are a pH problem wearing a disguise. - Wind, walls, weight and moving pots, which is the part nobody writes down until they have hurt their back. And the part that makes it usable Thirty-five short chapters, so you can read the one you need. A fault finder arranged by what you can see rather than by disease name. A chapter on received wisdom, grading the repeated advice against what was measured. Two printable worksheets — your site, and a pot register. And every number in the book on one printable page. What it is not Not a plant encyclopedia and not a pest and disease manual. Where the evidence is genuinely split — and on the gravel question it is — the book says so rather than picking the more quotable side. Where a figure comes from nursery trials on commercial crops, it says so, because a number measured on a production bench needs translating before you apply it to a balcony. Formats: PDF (US Letter, laid out page by page) and reflowable EPUB for Kindle, Kobo, Apple Books and phones. Both included. Instant download, nothing ships. Plain English throughout. Metric first, imperial in brackets. International by default.