Let's dig deeper into the world of companion planting, focusing on the best allies for our cherished tomatoes. Choosing the right companions can supercharge growth, enhance flavor, and ward off pests. But beware—there are a few plants that just don't play nice with tomatoes. Let’s explore the top tomato companions and the ones you might want to keep at arm’s length.

Good Companions for Tomatoes

1. Asparagus

These tall, fern-like perennials make great neighbors for tomatoes. Asparagus plants are low maintenance and won't compete heavily for nutrients, making them ideal companions in the garden bed.

In the book, Carrots Loves Tomatoes, author Louise Riotte explains how she grows asparagus in a long row at one side and plants tomatoes on either side once the spears are harvested in early spring. The tomato plants not only protect asparagus against asparagus beetles and reduces weeds around the asparagus, but the juice of the asparagus reduces the number of nematodes in the soil.

2. Chives

Besides adding zing to your dishes, chives are fantastic for deterring pests like aphids and spider mites, making them great tomato companion plants. Their strong scent can confuse pests looking for their favorite tomato treats. They also have complementary growth habits since chives grow low to the ground with shallow roots systems and tomato plants are taller with deeper root systems. Some say that chives improve the taste of tomatoes, but there is no evidence to support this.

In addition to the benefit of the aromatic leaves, chives produce small, purple flowers that attract beneficial insects like hoverflies and predatory wasps. These beneficials are natural enemies to many insects like whiteflies, aphids, and mealybugs that may attack your tomato plant.

3. Onions

Like chives, onions provide many of the same benefits. It will also repel certain beetles. In addition to insects, you can plant onions to keep away mammals like voles, rabbits, squirrels, chipmunks, and deer that don’t like the smell. Do you want to know how to get this to work? You need to create an impenetrable barrier by planting the bulbs closer (like an inch apart) in a line around the garden.

Did you know that onions can prevent diseases? And I’m not talking about putting an onion in your sock when you are sick (although that is done). Based on an article in the Journal of Fungi, onions produce toxic molecules that can affect soil-based fungal diseases, such as those causing damping off in tomato seedlings and Fusarium wilt.

If you have already harvested your onions but still want their repellent benefits, you can steep onions in your watering can by placing sliced onions in them and leaving the can in the sun for a few hours. Water the plants, especially the leaves, to get the repelling effect. You have to reapply after a rain or if you wet the leaves watering them.

4. Parsley

Planting parsley between tomato plants serves several benefits.  They are mutually beneficial in that parsley provides ground cover from weeds and tomato plants help parsley by providing shade during the heat of summer. Although the real benefit is when it flowers.

The small, fragrant flowers of parsley attract beneficial insects like hoverflies and parasitic wasps, which prey on tomato pests such as aphids, mealybugs, and caterpillars. This is a long-term game since parsley is a biennial plant that flowers in its second year and the leaves are no longer eaten for culinary purposes. To remedy this dilemma, plant new parsley each year to eat and leave the previous crop to flower. Keep in mind that you may get caterpillars, such as Eastern black swallowtails, munching on your foliage since parsley is a host plant.

5. Marigold

Known for their vibrant colors, marigolds are champions at repelling nematodes in the soil, which can be harmful to tomatoes. To get the most benefit, plant French or African marigolds densely as a cover crop then place tomatoes in the same spot as some of the marigolds.

Additionally, their strong scent can deter other pests like aphids, whiteflies and beetles while attracting beneficial insects such as ladybugs and hoverflies, as well as pollinators. They also trap spider mites and slugs.

6. Nasturtium

These pretty, edible flowers not only attract pollinators like bees but also repel aphids and whiteflies that can trouble tomato plants. Nasturtiums act as a sacrificial trap for pests, especially aphids, drawing them away from your precious tomatoes.

Nasturtiums can act as a living mulch, reducing the amount of evaporation around your tomato plants especially in the hot summer when tomatoes are super thirsty.

7. Carrot

Beneath the soil, carrots and tomatoes make great companions. Carrots help loosen the soil with their root growth, making it easier for tomatoes to establish deep, healthy roots. Carrots tend to be light nutrient feeders compared to the heavy nutrient feeders of tomatoes, so the carrots don’t steal nutrients. The foliage of carrots will suppress weed growth while the foliage of tomatoes shade carrots that are more sensitive to heat.

8. Garlic

A natural pest deterrent, garlic is excellent for keeping common tomato pests like aphids, spider mites, and even slugs at bay. Planting garlic around tomatoes can create a protective barrier against these unwanted visitors. Keep in mind that garlic requires a long growing period and needs to be started in the fall and harvested in the spring.

9. Basil

These herbs are classic companions for tomatoes. Basil not only enhances the flavor of tomatoes but also repels tomato hornworms. Their lower growth complements the upward growth of tomatoes. Since basil commonly gets downy mildew, I’ve been planting ‘Prospera’, a downy mildew-resistant variety. It can get quite large if given the space and flower excessively, attracting many bees. I also like using African blue basil, mainly to attract pollinators, rather than harvesting the foliage for dishes.

10. Borage

Borage, with its beautiful blue flowers, attracts bees and other pollinators while deterring tomato hornworms. It also serves as a trap crop for aphids. This year I saw aphids all over the plant, but they were all eliminated naturally and never went to my nearby tomato. The flowers attract the parasitic wasps which laid eggs in the aphids, ultimately killing them.

These flowers produce more ethylene gas which triggers fruit ripening, so it can decrease the time it takes for tomatoes to ripen. Another benefit is that the shed leaves break down to release calcium and potassium into the soil, decreasing the amount of blossom end rot (as long as give your tomato adequate water to absorb the calcium).

By planting these alongside your tomatoes, you create a diverse ecosystem that supports healthier plants and boosts your harvest.

Companions to Avoid with Tomatoes

1. Brassicas (Cabbage, Broccoli, Cauliflower)

While brassicas are great garden vegetables, they can compete for nutrients and space, potentially stunting tomato growth. Keep them separate in your garden beds.

2. Fennel

Fennel excretes chemicals that can inhibit tomato growth, so it's best to keep these plants apart. Fennel's expansive root system can also compete with tomatoes for water and nutrients.

3. Potatoes

Both tomatoes and potatoes belong to the nightshade family. Planting them together can increase the risk of diseases like blight spreading between the crops. Rotate their positions yearly to reduce disease pressure.

4. Corn

Corn plants can cast too much shade and outcompete tomatoes for sunlight and nutrients, leading to reduced yields for both plants. Keep these two crops in separate areas to optimize their growth. Corn and tomato also have a shared enemy - tomato fruitworm if on tomato or corn earworm if on corn. This caterpillar bores into the fruit and causes a mess.

Conclusion

So are you totally confused on what to plant next to your tomato? Remember, companion planting is a fascinating way to work with nature and boost the health of your garden, but you don't have to do them all at the same time. Observing how different plants interact and support each other is all part of the joyful journey of gardening! You can try one or two of the plants close to your tomato plants and others in the same garden bed. 

Do you have any favorite tomato companions or tips for successful gardening? Share them below—I’d love to hear from you! Happy gardening! 🍅🌱