When I first heard about companion planting – the idea that certain plants grow better together while others should be kept apart – I was skeptical. It seemed like garden folklore, the kind of thing people repeated without real evidence. So I planted my garden however it made sense visually, mixing vegetables and flowers without much thought to what went next to what.
Then a gardening mentor convinced me to try a few proven combinations. I planted basil next to my tomatoes, marigolds throughout my vegetable beds, and beans near my corn. The difference was noticeable – fewer pest problems, healthier plants, and better yields than I’d gotten planting everything randomly.
That experience converted me. While not every companion planting claim holds up under scientific scrutiny, many combinations genuinely work. Some plants repel pests that attack their neighbors. Others attract beneficial insects. Some improve soil for nearby plants or provide physical support.
Understanding companion planting isn’t about memorizing complicated charts of what can and can’t be planted together. It’s about learning a few key principles and proven combinations that make your garden more productive and require less intervention. This guide covers the combinations that actually work based on both research and generations of gardening experience.
The Science Behind Companion Planting
Companion planting works through several mechanisms, some well-documented and others still somewhat mysterious.
Pest confusion happens when aromatic plants mask the scent of their neighbors. Pests that find host plants by smell get confused and move on. This is why strongly scented herbs planted near vegetables can reduce pest damage.
Cabbage moths looking for plants to lay eggs on follow scent cues. Planting aromatic herbs nearby disrupts this, reducing caterpillar problems on brassicas.
Trap cropping uses sacrificial plants that pests prefer to valuable crops. Nasturtiums attract aphids so strongly that they’ll choose nasturtiums over nearby vegetables. You can then remove the infested nasturtiums, eliminating the aphid population.
I plant nasturtiums specifically for this purpose now. They become aphid magnets, protecting my roses and vegetables. When they’re covered with aphids, I pull them up and throw them away – pests and all.
Beneficial insect attraction is one of the most reliable benefits. Flowering plants throughout vegetable gardens provide nectar and pollen for predatory insects and parasitic wasps that control pests.
My gardens have far fewer pest problems since I started interplanting flowers with vegetables. Ladybugs, lacewings, and tiny wasps patrol constantly, eating aphids and other pests before populations explode.
Allelopathy involves plants releasing chemicals that affect nearby plants – sometimes beneficially, sometimes harmfully. Black walnut trees are famous for releasing juglone, which inhibits many plants. But some plants release beneficial compounds that suppress weeds or improve soil.
Physical benefits include plants providing shade, wind protection, or structural support for neighbors. The classic “Three Sisters” combination (corn, beans, squash) exemplifies this – corn provides structure for beans to climb, beans fix nitrogen, and squash shades soil to retain moisture and suppress weeds.
Spatial efficiency comes from combining plants with different growth patterns. Deep-rooted plants paired with shallow-rooted ones don’t compete as directly. Fast-growing crops harvest before slow-growing neighbors need the space.
Classic Companion Planting Combinations
These tried-and-true partnerships have proven themselves over generations of gardening.
Tomatoes and Basil
This is probably the most famous companion planting combination, and it genuinely works. Basil planted near tomatoes may repel certain pests (though research on this is mixed) but definitely attracts beneficial insects with its flowers.
More importantly, basil and tomatoes have similar water and nutrient needs, making them easy to care for together. And harvesting them together for cooking is wonderfully convenient.
I plant basil transplants around my tomato plants every year – at least three to four basil plants per tomato. They fill in nicely between tomato plants, and I harvest basil continuously all summer.
The Three Sisters
Native Americans developed this ingenious combination of corn, beans, and squash planted together. Corn provides a living trellis for beans to climb. Beans fix atmospheric nitrogen, enriching soil for all three plants. Squash spreads across the ground, shading soil to retain moisture and suppress weeds while its prickly leaves deter pests.
This works best with varieties suited to the technique – tall, sturdy corn; pole beans rather than bush beans; and vining squash. Modern hybrid sweet corn isn’t ideal as it’s often too short and weak to support beans well.
I’ve grown Three Sisters in a dedicated bed for several years. It’s more about enjoying the tradition and the self-sufficient beauty of the system than maximizing production – you can grow more of each crop separately – but it’s incredibly satisfying.
Carrots and Onions
Companion planting lore says these two repel each other’s pests – onion flies avoid carrots while carrot flies avoid onions. Scientific evidence for this is limited, but many gardeners swear by the combination.
What definitely works is spatial efficiency – onions are upright with minimal foliage while carrots grow underground. They don’t compete much and make good use of limited space.
I alternate rows of carrots and onions in spring. Whether it reduces pest problems or not, it certainly doesn’t hurt and uses space efficiently.
Marigolds Everywhere
Marigolds are the gateway companion plant – most gardeners start here. French marigolds (Tagetes patula) are said to repel various pests and suppress certain soil nematodes.
Research supports some claims. Marigolds do reduce certain nematode populations when planted densely. Their scent may repel some pests, though probably not as dramatically as folklore suggests.
What’s certain is that marigolds attract beneficial insects, add cheerful color, and don’t hurt anything. I plant them throughout my vegetable garden not because I think they’re miracle pest repellents but because they’re attractive, easy, and attract beneficials.
Nasturtiums as Trap Crops
I mentioned this earlier but it deserves emphasis. Nasturtiums attract aphids so strongly that they protect nearby plants. They also attract beneficial insects with their flowers and add edible flowers and leaves to salads.
Plant nasturtiums near aphid-susceptible plants like roses, beans, and brassicas. Check them regularly and remove heavily infested plants before aphids spread.
Herbs with Brassicas
Brassicas (cabbage family plants) suffer from various pests including cabbage moths, aphids, and flea beetles. Aromatic herbs planted nearby – especially dill, rosemary, sage, and thyme – may confuse pests through scent masking.
I interplant herbs throughout my brassica beds now. It looks beautiful, provides herbs for cooking, and my cabbage and broccoli definitely have fewer pest problems than when planted alone.
Plants That Support Each Other
Beyond pest control, some plants actively help their neighbors grow better.
Nitrogen Fixers
Legumes (peas, beans, clover) have root nodules containing bacteria that convert atmospheric nitrogen into forms plants can use. While the nitrogen primarily benefits the legumes themselves, some becomes available to neighbors, especially after legume roots decompose.
Plant nitrogen-fixing cover crops before heavy feeders like corn or tomatoes. Or interplant beans with nitrogen-hungry crops.
Dynamic Accumulators
Some plants have deep roots that mine nutrients from subsoil, bringing them up where shallow-rooted plants can access them. When these deep-rooted plants are cut and left to decompose, nutrients become available to neighbors.
Comfrey is the classic example – its roots reach deep to access minerals, and its leaves make excellent mulch or compost material. Dandelions (yes, the weeds) also accumulate nutrients from deep soil.
I grow comfrey specifically to harvest leaves for mulch around other plants. It’s ugly but incredibly useful.
Shade Providers
Tall plants providing afternoon shade help heat-sensitive crops extend their season. Lettuce planted in the shade of tomatoes or trellised beans lasts weeks longer before bolting.
I plant lettuce, spinach, and other greens on the east side of tall plants where they receive morning sun but afternoon shade. This extends my harvest by a month or more in summer.
Combinations to Avoid
Some plants genuinely inhibit each other’s growth through allelopathy, competition, or disease spread.
Fennel
Fennel is allelopathic and inhibits most plants near it. Plant fennel alone, well away from vegetable gardens. I learned this the hard way when fennel stunted nearby vegetables.
Brassicas and Strawberries
These share some diseases and pests, so planting them together increases problems for both. Keep them separated in your garden plan.
Beans and Alliums
Beans and onion-family plants (onions, garlic, leeks) don’t grow well together. The growth inhibition is documented though the mechanism isn’t entirely clear.
I avoid planting beans near onions now. It’s easy enough to keep them in different beds.
Potatoes and Tomatoes
Both are in the nightshade family and share many diseases. Planting them together increases disease pressure on both. This also applies to crop rotation – don’t follow tomatoes with potatoes or vice versa.
Designing a Companion-Planted Garden
Incorporating companion planting doesn’t require complicated plans. Start with these principles:
Interplant flowers throughout vegetable beds to attract beneficial insects. This is the single most effective companion planting strategy. I use calendula, cosmos, zinnias, and alyssum throughout my gardens.
Edge beds with herbs – thyme, oregano, sage, and other aromatic herbs create a scent barrier while providing kitchen herbs. They’re attractive, functional, and require minimal maintenance.
Vertical layering combines plants of different heights. Tall corn or tomatoes in back, medium-height peppers or beans in the middle, low-growing lettuce or herbs in front. This maximizes space and light while creating beneficial microclimates.
Succession plant to maintain continuous beneficial insect populations. As early crops finish, replace them with something flowering. I follow spring peas with summer basil, keeping flowers continuously available.
Create permanent flowering strips or islands within vegetable gardens. I have a small bed of perennial flowers (yarrow, catmint, coneflowers) in the middle of my vegetable garden specifically to support beneficials year after year.
Herbs as Universal Companions
Most culinary herbs make excellent companion plants throughout gardens. They’re aromatic (potentially confusing pests), attract beneficial insects when flowering, and add beauty and function.
Basil goes with almost everything, especially tomatoes and peppers. It attracts pollinators and beneficial insects while providing leaves for cooking.
Dill attracts beneficial insects in huge numbers when flowering – ladybugs, lacewings, and tiny parasitic wasps swarm to dill flowers. Plant it near vegetables with aphid problems.
Oregano and thyme are perennial herbs that create permanent beneficial insect habitat while adding cooking herbs and attractive flowers.
Cilantro (coriander) attracts beneficials and provides culinary leaves and seeds. Let some plants flower for the beneficial insects.
Mint is too aggressive to plant directly in beds (it spreads aggressively), but potted mint placed near gardens may repel some pests while providing leaves for tea and cooking.
I have herbs scattered everywhere in my garden now – they’ve become essential rather than optional. The combination of beauty, function, and culinary use makes them perfect companions.
Flowers That Earn Their Space
These flowers provide serious benefits beyond beauty:
Alyssum – This low-growing annual attracts hoverflies whose larvae devour aphids. Planted densely at bed edges, it creates a carpet of flowers and beneficial insect habitat.
Calendula – Attracts beneficial insects, repels some pests, and has edible petals. It self-seeds readily, coming back year after year.
Zinnias – Attract butterflies and other beneficials, provide cut flowers, and tolerate heat beautifully. I plant zinnias throughout my vegetable garden now.
Cosmos – Tall, airy flowers that don’t shade nearby plants but attract numerous beneficials. They bloom prolifically with zero maintenance.
Sunflowers – Attract pollinators and beneficial insects, provide structure for climbing plants, and produce seeds for birds and people.
The Bottom Line on Companion Planting
Not every companion planting claim is scientifically proven, and that’s okay. What matters is that many combinations genuinely help while none actively hurt (except the few known antagonistic pairs to avoid).
Start simple – add marigolds and flowers throughout your vegetable garden. Plant basil near tomatoes. Include aromatic herbs at bed edges. These basics will improve your garden noticeably.
As you gain experience, experiment with other combinations. Keep notes about what works in your specific conditions. Every garden is different, and discovering what works for you is part of the journey.
The goal isn’t creating a garden according to a rigid companion planting chart. It’s building a diverse, balanced ecosystem where plants, insects, and soil life work together to create abundance with less intervention from you.
That’s what companion planting is really about – working with nature’s relationships rather than fighting against them.
