30 studies, every one cited on the page where it is used. "Herbs" is not a crop. It is a shelf in a supermarket. The plants on it come from different genera and different climates, and they were grouped by what you do with them in a kitchen — which is why a single windowsill, a single watering can and a single grow light will always be wrong for some of them. How wrong: sweet basil's optimum temperature is 32.6–35.5 °C. Sage's is 23.5–27.5 °C. And as you give them more light those two optima move in *opposite directions* — basil's rises, sage's falls. Turn up the lamp for the whole rack and you push them further apart. Then there is the second target nobody separates from the first. Growing a herb and growing its flavour are not the same thing, and for several species they pull against each other: the conditions that build the most leaf are not the conditions that build the most essential oil. This book treats those as two dials, because that is what they are. What is in it - Where the smell actually lives, why the plant makes it, and what that means for how you grow and when you cut. - The temperature table that breaks the category. Measured optima per species, and how each one moves as light rises — sage falling 27.5 → 23.5 °C, spearmint 30.4 → 27.8 °C, sweet basil *rising* 32.6 → 35.5 °C. - Light, from scratch — the only number that matters, how to measure it when your eye adapts across three orders of magnitude and lies to you, what the glass takes out, how to choose and hang a lamp, and the hours question. - Purple basil as a thermometer. It is green at 35 °C whatever the light, and properly purple only near 25 °C with high light. The colour is a readable record of the conditions, not a labelling mistake. - Cold, and the windowsill trap. Basil takes chilling damage below 12 °C and severe damage below 10 °C; leaves blacken in one day at 0 °C and three days at 5 °C. A plant pressed against winter glass overnight goes below that while the room thermostat reads 19. - Why refrigerating cut basil strips the aroma — nine days at 4 °C measurably lowered volatiles, polyphenols and antioxidants against 12 °C. - Bolting, the stress dial, watering, dry air and moving air — four things that are all really one thing once you can see the mechanism. - Harvesting as farming, not picking. When to cut, how much, and how to keep a pot producing for months instead of killing it in three weeks. - The supermarket pot, and what to do with it — because it was grown to be sold, not to survive. - Drying, freezing and oil, with what each does to the compounds you grew it for. And the part that makes it usable Thirty-five short chapters. Ten herbs, by the numbers — a species-by-species table you can grow from. A fault finder arranged by what you can see. Two printable worksheets — a light survey and a cutting log. And every number in the book on one printable page. What it is not Not a cookery book and not a herbal medicine guide. No therapeutic claims are made anywhere in it. Where a figure comes from controlled-environment research rather than a windowsill, the book says so, because a number measured under constant light needs translating before you apply it to a north-facing kitchen in February. 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.