Companion and antagonistic plants: a practical table
Companion planting means putting together species that help one another: one draws pollinators, another fixes nitrogen, another covers the soil. Not every pair works — some actively harm each other. This is the short list worth knowing before you plant.
Companion planting is not magic: mostly it is space, light, water and roots. Two plants with identical needs compete; two with different needs share a bed happily. On top of that, some bring extra functions — scent that confuses pests, flowers that feed beneficial insects, roots that lift nutrients.
Pairings that work
| Plant | Goes with | Why |
|---|---|---|
| BasilOcimum basilicum | Tomato, pepper | Strong scent that confuses whitefly and aphids; occupies the ground layer without stealing light. |
| French marigoldTagetes patula | Root vegetables, tomato | Its roots release compounds that suppress soil nematodes. |
| NasturtiumTropaeolum majus | Brassicas, young fruit trees | A trap crop: aphids prefer it and leave the main crop alone. |
| GarlicAllium sativum | Roses, stone fruit | Sulphur compounds slow fungal disease and deter aphids. |
| White cloverTrifolium repens | Any fruit tree | Fixes nitrogen and covers the soil under the tree, cutting watering and weeding. |
| PhaceliaPhacelia tanacetifolia | The whole garden and orchard | One of the best flowers for bees and hoverflies — whose larvae eat aphids. |
| BorageBorago officinalis | Strawberry, squash | A long flowering season that secures pollination; leaves usable as mulch. |
| ComfreySymphytum officinale | Fruit trees | Deep roots lift potassium; cut leaves feed the surface as mulch. |
Pairings to avoid
| Plant | Keep away from | Why |
|---|---|---|
| FennelFoeniculum vulgare | Almost everything | Releases compounds that suppress germination and growth in its neighbours. Give it its own corner. |
| WalnutJuglans regia | Tomato, apple, many shrubs | Produces juglone, toxic to many species. Allow for the canopy area plus a few metres. |
| OnionAllium cepa | Beans, peas and other legumes | Alliums inhibit the bacteria that fix nitrogen on legume roots. |
| CabbageBrassica oleracea | Strawberry | They compete for the same nutrients at the same depth and share diseases. |
| SpearmintMentha spicata | Open beds | Not toxic, just invasive: it spreads by rhizome and takes the bed over. Plant it in a sunken pot. |
Think in layers, not in pairs
In a food forest the scale of the question changes: instead of two neighbours you design a group around one tree — a guild. The practical rule is to cover functions, not to fill space.
- A main tree, giving structure and shade.
- A nitrogen fixer, feeding the group.
- A flowering plant for pollinators and beneficial insects.
- A ground cover, holding back weeds and evaporation.
- A deep-rooted accumulator, lifting nutrients.
Five or six well-chosen plants do more than twenty picked at random — and they are far easier to actually find at a nursery near you.
Does companion planting really work?
Some relationships are well documented — nitrogen fixation, trap crops, flowers that attract beneficial insects. Others are garden tradition without solid evidence. Use the first group and treat the second as an experiment.
How far apart should companion plants be?
It depends on the mature size, not the size you buy. Allow for each plant's final canopy diameter and never leave the companion in permanent shade.
Can I plant everything at once?
Usually not. The tree goes in first, while dormant; herbaceous plants and ground covers follow once the tree has established.