Basil Companion Plants
Ocimum basilicum · mint family · rotation group: other
The best companion plants for basil are Tomato, Pepper, Lettuce, Marigold, and Nasturtium. Avoid planting basil near Rue, Fennel, Rosemary, Oregano. Of the 10 pairings recorded here, 1 is supported by published research and 9 are traditional practice with no controlled evidence behind them.
What to plant with basil
| Plant | Claimed benefit | Evidence | What the evidence actually shows |
|---|---|---|---|
| Tomato | Basil grown with tomatoes reduces thrips and may promote tomato growth. | Research-backed | Extension cites field and greenhouse studies showing reduced thrips; the mechanism is most likely volatile masking by linalool and eucalyptol. The flavor-improvement claim remains untested. |
| Borage | Borage improves basil vigour and draws pollinators to the bed. | Traditional | Borage is a proven pollinator magnet, but basil is harvested for leaf and gains nothing measurable from pollination. |
| Lettuce | Basil and lettuce share a bed well, with basil taking over as lettuce bolts. | Traditional | A succession and space convention rather than a tested interaction. |
| Marigold | Marigold alongside basil deters pests from the herb bed. | Traditional | The marigold results that hold up are whitefly protection of tomato and nematode suppression as a pre-crop; neither applies to basil. |
| Nasturtium | Nasturtium traps aphids away from basil. | Traditional | Nasturtium's proven trap-crop record is against squash bugs and cabbage caterpillars, not aphids on basil. |
| Pepper | Basil shelters peppers and deters their pests. | Traditional | Extrapolated from the tomato work; no pepper trial exists. |
What not to plant with basil
| Plant | Claimed problem | Evidence | What the evidence actually shows |
|---|---|---|---|
| Fennel | Fennel inhibits basil growth. | Traditional | Fennel essential oil suppresses seed germination in laboratory bioassays; no garden trial has tested it against basil. |
| Oregano | Basil's need for steady moisture conflicts with oregano's demand for dry, sharply drained soil. | Traditional | A cultural conflict rather than a chemical one: watering to suit basil will eventually rot oregano's roots and crown. Grow both, but in separate containers or at opposite ends of a bed. The older claim that pairing aromatic herbs reinforces pest 'masking' does not hold up — Finch et al. (2003) found the effect attributed to herb scent is largely visual interference with insect landing, not odour. |
| Rosemary | Rosemary and basil are poor bedfellows. | Traditional | This is a cultural mismatch rather than an antagonism: rosemary wants dry lean soil while basil wants steady moisture and feeding. |
| Rue | Rue planted near basil stunts it. | Traditional | A very old prohibition with no supporting data; rue does produce phototoxic furanocoumarins, but no allelopathic effect on basil has been measured. |
The honest verdict
Of everything gardeners recommend planting alongside basil, 1 pairing has been tested properly: Tomato. Those are the ones worth planning your bed around.
The remaining 5 pairings on this page are traditional practice. They circulate on every companion planting chart online, but we could not find controlled evidence testing them. They are not wrong so much as unverified — most cost nothing to try, and interplanting flowers and herbs has its own well-documented benefit of pulling pollinators and predatory insects into the garden.
Every row above links to the publication it came from. See how we grade evidence.
Growing basil: the numbers
| Sun | Full sun (6+ hours) |
|---|---|
| Water | Moderate |
| Spacing | 12 in apart · 18 in between rows · 1 per square foot |
| Mature size | about 24 in tall |
| Soil pH | 6–7.5 |
| Days to maturity | 60–90 days |
| Frost tolerance | Tender — killed by frost |
| Containers | Yes — 2 gallon minimum |
| Typical yield | cut-and-come-again; repeated harvests all season |
| Common pests | Japanese beetle, aphids, slugs, spider mites |
| Common diseases | basil downy mildew, Fusarium wilt, root rot, gray mold |
When to plant basil
Zone 6b shownStart seeds indoors: Feb 13 – Feb 27 — 6–8 weeks before your last frost
Direct sow outdoors: Apr 17 – Apr 30 — 1 week after last frost
Transplant outdoors: Apr 24 – May 7 — 2 weeks after last frost
Expected harvest: Jun 23 – Jul 23 — 60–90 days from planting
Those dates are for zone 6b. Get your own dates by ZIP code →
Varieties worth knowing
seeds- Genovese — classic sweet Italian pesto type
- Spicy Globe — dwarf bush type, small leaves, best basil for containers
- Dark Opal — purple-leaved ornamental and culinary type
- Siam Queen — Thai basil, anise-clove flavor
Variety names link to seeds on Amazon. As an Amazon Associate we earn from qualifying purchases. These are the varieties named in the extension sources for this crop, not a paid placement — where a source recommended a variety for a specific reason, that reason is the note beside it.
Put it in a bed
The garden planner checks every square against this ledger as you place crops — if you drop basil next to something recorded as a bad neighbour, the square turns red and tells you why.
Records for the plants named above:
Same rotation group (other) — don't follow one with another:
Basil companion planting questions
What should not be planted next to basil?
How far apart should basil be planted?
Does companion planting with basil actually work?
When should I plant basil?
Sources for this record
- Growing basil in home gardens, University of Minnesota Extension
- Herb Garden Plants: Basil, Penn State Extension
- Basil, Herbs, University of Illinois Extension
- Cultural Tips for Growing Basil, UC IPM
Record compiled 2026-07. Spot an error or a study we missed? Tell us and we'll correct the entry.