We do not invent trials, universities, scientists, statistics or quotations. Where the published evidence is thin, we say so rather than filling the gap.
Each note below states an answer, the strength of the evidence behind it, what remains unknown, the sources we relied on, and the date we last checked them. If a claim cannot be sourced, it does not appear here — and it is not published as news.
Evidence · Well established in horticultural guidance
Do bigger pots really grow better tomatoes?
Root volume matters up to a point. Standard guidance is a minimum of about 10 litres per plant for containers, with larger volumes making watering and feeding far more forgiving.
What the evidence says
The RHS advises growing tomatoes in large containers or growing bags, planting no more than two plants per standard bag, because restricted root volume dries out and starves plants quickly.
Container-grown plants need more frequent watering and a regular high-potassium feed once the first fruits set — the smaller the container, the less margin for error.
Erratic watering in small containers is associated with blossom end rot and fruit splitting, which is why volume behaves like a buffer rather than a growth stimulant on its own.
What we do not know
We are not aware of a public, controlled UK trial comparing yields across a range of pot sizes for named varieties under identical feeding. The Tomato Post has not run one. Any figures you see quoted as a precise yield gain should be treated sceptically.
Evidence · Reasonable published evidence
Why do some tomatoes taste so much better than others?
Flavour is sugars and acids plus a set of volatile aroma compounds. Peer-reviewed work found that modern commercial varieties have lost some of those volatiles, which is why sugar content alone does not predict taste.
What the evidence says
Tieman and colleagues, publishing in Science in 2017, identified chemical changes — including reduced levels of key flavour volatiles — associated with the decline in flavour of modern commercial tomatoes.
That work supports panel tasting that separates sweetness, acidity and aroma rather than reporting a single score or a Brix reading.
Ripeness at picking and post-harvest chilling also affect aroma, which is a handling question as much as a genetics one.
What we do not know
Published chemistry does not translate neatly into a ranking of garden varieties. Our own Taste Lab records are reader observations, not laboratory measurements, and are labelled as such.
Evidence · Well established in horticultural guidance
Should you pinch out side-shoots?
Yes for cordon (indeterminate) varieties grown up a support; no for bush (determinate) varieties, where removing shoots removes the crop.
What the evidence says
RHS guidance is to remove side-shoots from cordon tomatoes as they appear and to stop the main stem after a set number of trusses, so the plant ripens what it has.
Bush and trailing types are left unpruned; their fruit forms on the side growth.
Getting the type wrong is one of the most common reasons a healthy-looking plant produces very little.
What we do not know
How many trusses to stop at varies with site, season and heat. Published guidance offers ranges, not a single correct number.
Evidence · Reasonable published evidence
Can you prevent tomato blight?
You cannot stop the spores, but you can reduce risk: grow under cover, keep foliage dry, space plants, and choose varieties with published blight resistance.
What the evidence says
Late blight (Phytophthora infestans) spreads in warm, wet conditions; RHS guidance emphasises ventilation, avoiding overhead watering and removing affected material.
Fight Against Blight, run by the James Hutton Institute, tracks blight outbreaks and genotypes across Great Britain from samples submitted by growers.
Some varieties are sold as blight-resistant; resistance is partial and can be overcome by newer genotypes, so it reduces rather than removes risk.
What we do not know
Local risk in any given week depends on weather that we do not measure. We report outbreak monitoring published by others and do not issue our own forecasts.