Why Your Plants Aren’t Thriving (And How Companion Planting Can Fix It!)

Imagine throwing a dinner party. You carefully curate the guest list—some people just get along better than others. Plants are no different. Some thrive when planted together, boosting each other’s growth, repelling pests, and improving flavour. Others? Well, let’s just say they bring the drama. Welcome to the world of companion planting, where plant friendships (and feuds) can make or break your garden.

 

What Is Companion Planting?

Companion planting is the strategic placement of plants that benefit each other when grown side by side. Some plants provide shade for their neighbours, while others release natural compounds that repel pests or improve soil quality. There are even plants that help enhance the flavour of their companions, making them better both in the garden and on your plate. However, just like in any social setting, some plants do not get along. Certain pairings can lead to stunted growth, increased pest problems, or competition for nutrients, ultimately resulting in a lackluster garden. Understanding which plants are allies and which are rivals is the key to making companion planting work.

Why Should You Companion Plant?

Besides making your garden look more diverse and vibrant, companion planting offers numerous practical benefits. One of the biggest advantages is natural pest control. Some plants, like marigolds, produce chemicals that deter harmful insects, keeping their neighbouring crops safe. Other companions improve growth and flavour—for instance, basil planted near tomatoes not only repels pests but also enhances the tomatoes’ taste. Companion planting can also maximize space efficiency by pairing tall, sun-loving plants with shorter, shade-tolerant ones. Additionally, some plants, like peas and beans, are nitrogen-fixers, meaning they enrich the soil with nutrients that benefit nearby crops. Lastly, companion planting helps suppress weeds, as densely packed plants create natural ground cover, reducing the chances of unwanted intruders taking over.

 

How to Companion Plant

The first step in companion planting is to know which plants support each other and which ones should be kept apart. Pairing the right plants can make your garden healthier and more productive. Next, consider their growth habits—tall plants like corn can provide shade for delicate greens, while vining plants like cucumbers can benefit from natural trellises such as corn stalks. Mixing different plant types together also helps confuse pests, making it harder for them to zero in on their favourite food sources. Herbs like basil, dill, and parsley are excellent garden defenders, repelling unwanted insects while attracting beneficial pollinators.

Perfect Plant Partnerships

Some plants are natural allies and thrive when grown together.

Tomatoes do well when:

Planted near marigolds, parsley, basil, spinach, and garlic. Marigolds help deter pests, basil enhances tomato flavour, spinach benefits from the shade of the tomato plant, and garlic acts as a natural anti-fungal agent. 

Peas pair well with:

Beans, cucumbers, corn, and carrots. The nitrogen from peas enriches the soil for beans, cucumbers benefit from the vertical support of corn stalks, and carrots make good space-efficient neighbours. 

Peppers thrive alongside:

Basil, onions, eggplant, and carrots, as basil keeps pests away while onions and carrots improve overall soil conditions. 

Cucumbers flourish near:

Marigolds, peas, dill, and nasturtiums—marigolds and nasturtiums repel harmful insects, while dill attracts beneficial pollinators. 

Onions grow best when:

Paired with beets, carrots, parsnips, and nasturtiums, all of which contribute to balanced soil health and pest deterrence.

Carrots are great friends with:

Cabbage, leeks, radishes, peas, lettuce, sage, and rosemary. Peas and lettuce provide light shade, while sage and rosemary help deter carrot flies.

Potatoes thrive with:

Peas, beans, cilantro, lettuce, and marigolds—marigolds fend off nematodes, while peas and beans improve soil fertility.

Lettuce grows well alongside:

Beets, spinach, peas, cucumbers, and dill, with dill attracting pollinators and cucumbers offering shade to keep lettuce cool.

Beyond these common pairings, some classic companion plant groupings have been used for generations. One of the most famous is:

The Three Sisters (Indigenous) 

Corn, beans, and squash. In this trio, corn provides a natural trellis for the beans, beans fix nitrogen into the soil to nourish the corn and squash, and squash acts as a living mulch, shading the soil to retain moisture and prevent weeds. 

Carrots & Onions

Onions deter carrot flies, while carrots keep onion flies at bay. Lettuce and radishes also work well together; radishes grow quickly, breaking up the soil and making room for lettuce to establish itself. 

Cabbage & Dill 

Cabbage & Dill are a powerhouse combination, with dill attracting beneficial insects that keep cabbage worms under control.

Herb Companion Plants

Herbs are the quiet powerhouses of the companion planting world. They repel pests, enhance flavours, and even improve soil conditions.

Basil thrives next to:

Parsley, oregano, and thyme. These herbs create a microclimate that helps retain soil moisture while boosting each other’s flavours.

Dill pairs well with:

Lavender, fennel, and coriander. Lavender attracts pollinators, while fennel and coriander work together to deter aphids and other pests.

Mint loves growing with:

Cilantro, kale, and radishes. It acts as a natural pest repellent, keeping insects away from leafy greens and root vegetables. However, be cautious—mint spreads aggressively, so plant it in a container or an isolated area.

Oregano benefits from being planted alongside:

Basil, thyme, and sage. These Mediterranean herbs thrive in similar soil conditions and work together to repel pests like cabbage moths and aphids.

 

What Happens When Plants Don’t Get Along?

Not all plants are meant to be neighbours, and planting the wrong pairings together can cause serious issues. For example:

Tomatoes and potatoes:

They should never be grown side by side, as they both attract the same blight, which can quickly devastate your crops.

Beans and onions

Are another poor combination—onions release compounds that can stunt the growth of beans.

Carrots and dill

You'd think they should be friends, but dill can actually inhibit carrot growth and alter its flavour.

Cabbage and strawberries

They also make bad neighbours, as cabbage plants tend to overshadow and choke out strawberry plants, limiting their fruit production.

The Bottom Line

Companion planting is a mix of science, strategy, and a little bit of plant matchmaking. When done right, it leads to a healthier, more productive garden with fewer pests, richer soil, and better-tasting vegetables. With a little planning, you can create a thriving, low-maintenance garden where plants support each other and do some of the work for you. But be mindful—some plants just don’t get along, and pairing them together can spell disaster for your garden. Choose wisely, and your plants will thrive. Choose poorly, and you might find yourself dealing with a plant rivalry that makes your garden look like a battleground. 

 

So there you have it, plan your garden like you’d plan a great dinner party—invite the right guests, keep the troublemakers apart, and let nature take care of the rest! 

Happy gardening!