Tool — Form GL-2

Companion Plant Checker

Tick two or more crops and the checker returns a verdict for every pair — good, bad, or no record — with the strength of the evidence behind it. Of the 542 pairings on file, 129 are backed by published research, 379 are traditional practice nobody has tested, and 34 are widely repeated but not supported.

Check a pairing

Form GL‑2

Tick the crops you want to grow together. Every pair is checked against the ledger and returned with the strength of the evidence behind it — including the pairings where the honest answer is "no one has actually tested this."

Crops
Vegetables
Fruits
Herbs
Flowers

How to read a verdict

The stamp matters more than the verdict. A pairing marked research-backed has been measured in a controlled trial and is worth planning around. Traditional means the advice is old and plausible but untested — try it if you like, but don't rearrange a bed for it. Not supported means someone did test it and it didn't hold up.

Where nothing is recorded at all, the honest answer is that the combination simply hasn't been studied — which is true of the overwhelming majority of plant pairs. In that case fall back on the things that reliably matter: matching sun and water needs, giving each plant its recommended spacing, and keeping tall crops from shading short ones.

Planning a whole bed rather than checking a pair? The garden planner runs this same check on every square as you place crops.

Common questions

What does it mean when no pairing is recorded?
That the combination is neutral as far as the literature goes — nobody has recorded it as either beneficial or harmful. Most plant combinations are like this. Grow them together if their spacing, sun, and water needs line up, which is a far better guide than a companion chart.
Why does the checker disagree with the chart I found elsewhere?
Because most charts online copy each other without checking. Of the 542 pairings recorded here, only 129 have been tested in controlled research and 34 are repeated widely despite being tested and not supported. We publish the grade and the source for each one so you can judge it yourself.
Can I plant tomatoes and peppers together?
Yes — they want the same conditions and are not recorded as antagonists. The real caution is that they share a family (nightshades) and therefore share diseases like early blight, so keep them in the same rotation group and move that whole group each year rather than following tomatoes with peppers in the same soil.