The short version: of the 542 companion planting pairings recorded here, 129 are supported by published research, 379 are traditional practice with no controlled evidence behind them, and 34 are repeated constantly despite being tested and not supported. Companion planting is real, but a lot less of it is proven than the charts suggest.
What to plant with…
All 56 records →Tomato
8 companions, 4 to avoid · 2 research-backed
Entry No. 024Pepper (sweet/bell)
8 companions, 3 to avoid · 0 research-backed
Entry No. 013Cucumber
8 companions, 3 to avoid · 2 research-backed
Entry No. 039Strawberry
7 companions, 2 to avoid · 1 research-backed
Entry No. 026Potato
7 companions, 4 to avoid · 0 research-backed
Entry No. 041Basil
6 companions, 4 to avoid · 1 research-backed
Entry No. 009Carrot
8 companions, 3 to avoid · 1 research-backed
Entry No. 019Lettuce
8 companions, 3 to avoid · 1 research-backed
When to plant it where you live
Zone-accurateEnter a ZIP code and every date on this site re-derives from your zone's median frost dates — no more converting someone else's calendar to your climate.
Your planting calendar
Form GL‑6| Crop | Start indoors | Plant outside | Fall sowing | Harvest from |
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Tip: print this page for a calendar you can pin up in the shed.
Tools
Garden Planner
Lay out a raised bed square by square. Bad pairings turn red as you place them.
Form GL-2Companion Plant Checker
Tick the crops you want together and get a verdict on every pair.
Form GL-3Frost Date Lookup
Your zone, your first and last frost, your growing season length.
Form GL-4Raised Bed Soil Calculator
Bed size to cubic feet, bags, yards, and a mix recipe.
Form GL-5Plant Spacing Calculator
How many plants fit your bed, three different ways.
Form GL-6Planting Calendar
Every crop's sow, transplant, and harvest window for your zone.
Guides
All guides →Does companion planting actually work?
What the research supports, what it doesn't, and why the charts all disagree.
Starting seeds indoors
Counting back from your last frost, and the mistakes that cost you a month.
The best soil for raised beds
What to fill a new bed with, what it costs, and what to skip.
Square foot gardening
The spacing system, per-square plant counts, and where it breaks down.
Crop rotation made simple
Four groups, four beds, and why rotation beats most companion planting.
Garden layout plans
Ready-made bed plans with spacing and companion conflicts already resolved.
Why a ledger
A ledger is a record of what actually happened, entry by entry, with the source of each figure written next to it. That is the whole idea here. Gardening advice online is copied from chart to chart until nobody can say where a claim started or whether anyone ever checked it.
So every pairing on this site carries a stamp and a link. Where a university trial measured the effect, we say so and cite it. Where the only support is that everyone repeats it, we say that too — Traditional is the most common stamp on the site, and that is an honest description of the field rather than a failure of research. Read the grading method →