As I’ve researched organic gardening techniques, one of the most powerful discoveries I’ve made is that a garden bed should be treated as a living community. The success of a single kale plant isn’t just about the sun it gets or the water you provide; it’s profoundly influenced by its neighbors.
In the world of agricultural science, this is known as companion planting. What truly fascinated me in my research was learning that this is far more than just folklore. As Utah State University explains, it’s the intentional practice of growing plants together to enhance their mutual productivity and create a balanced ecosystem. It’s a strategy with a surprisingly long history, used for centuries to naturally deter pests, attract beneficial insects, and even enrich the soil.
In my main guide, How to Grow Kale from Seed to Harvest, I briefly introduce this concept. This article is where I’ll share the full results of my research, sifting through university studies to bring you a definitive guide to the best friends—and worst enemies—for your kale patch. My goal is to show you how to move beyond simply planting vegetables and start designing a small, thriving ecosystem—one that helps you keep bugs off your kale naturally.
How Companion Planting Works: The Science in Your Garden
To effectively design your garden ecosystem, I find it’s helpful to understand the scientific principles that make companion planting work. My research into university extension findings, particularly from Utah State University, shows that good companions help kale in several key ways:
- Confusing Pests with Scent Masking: Many pests, like the cabbage moth, find your kale by its unique scent. By interplanting strongly aromatic herbs (like the onions, garlic, and chives mentioned in the USU research), you create a confusing “cloud” of smells that makes it much harder for pests to locate their target.
- Attracting Beneficial Insects: This is my favorite part of the strategy—recruiting allies. Some companions act like a beacon for predatory insects. The research notes, for example, that dill is excellent at attracting ladybugs, which are voracious aphid eaters. Other flowers, like rosemary and thyme, attract valuable pollinators that can improve the overall health and yield of your garden.
- Using Sacrificial “Trap Crops”: This is a clever technique where you plant something that pests love even more than your kale. The USU guide highlights nasturtiums as a classic example. Aphids are drawn to the nasturtiums, leaving your kale alone. This concentrates the pests in one area, making them easy to manage, a method formally known as “trap cropping.”
By using a combination of these strategies, you’re no longer just a gardener; you’re an ecosystem designer.
The Best Friends: 10+ Excellent Companion Plants for Kale
Through my research into university extension guides and horticultural studies, I’ve categorized the most effective and scientifically-backed companions for kale not just by name, but by the specific job they do in your garden ecosystem.
Aromatic Herbs to Confuse Pests
This is my number one defensive strategy for any kale patch. Pests like the Cabbage Moth find your kale by its distinct scent. By interplanting intensely fragrant herbs nearby, you create an aromatic “cloud” that masks the smell of kale, essentially making your plants invisible to them.
- Rosemary, Thyme, Sage, and Oregano: These potent Mediterranean herbs are classic examples of using strong scents for pest control, a principle noted in university guides like the one from Utah State University. Their powerful essential oils create a protective aromatic shield. As a fantastic secondary benefit, the USU research also highlights that their flowers are powerful magnets for the helpful pollinators that improve your whole garden’s health.
- Mint: This is another powerful aromatic deterrent. However, a word of caution is essential: mint is incredibly invasive. I always plant it in a separate pot placed near my kale bed, never directly in the ground.
- Dill and Cilantro: These are double-duty champions. They not only add to the confusing cloud of smells, but their small flowers are magnets for beneficial insects. This is confirmed in university studies, which note that dill is particularly effective at attracting aphid-eating ladybugs and other predatory insects like lacewings.
The Allium Family: Your Garden’s Bodyguards
Another group of powerfully scented plants consistently recommended as pest deterrents is the Allium family. Their effectiveness is one of the most well-documented facts in companion planting literature.
- Garlic and Chives: These are particularly effective against aphids. The strong sulfurous compounds they release are disliked by many pests. I often keep a pot of chives nearby my brassica (kale) container to help deter pests.
- Onions: Planting onions between your kale plants can help deter cabbage worms and other caterpillars.
Flowers That Attract Allies & Act as Traps
Some flowers do more than just look pretty; they are hardworking members of the garden community, acting as both lures and hosts for helpful insects.
- Nasturtiums: These are the ultimate sacrificial plant and a perfect example of “trap cropping.” Aphids often prefer nasturtiums over kale, so the flowers attract the pests, concentrating them in one place and keeping them off your main crop. The Utah State University guide highlights nasturtiums as a classic trap crop for brassicas like kale, while also noting their flowers attract helpful pollinators.
- Marigolds: French Marigolds release a substance that can repel root-knot nematodes in the soil, protecting the root systems of your kale and other vegetables.
Legumes for a Nutrient Boost
Kale is a heavy feeder, meaning it uses a lot of nitrogen from the soil to produce those big, beautiful leaves. Legumes are the perfect partners to help replenish this vital nutrient.
- Bush Beans and Peas: These plants have a remarkable ability to partner with soil bacteria to capture nitrogen directly from the air and convert it into a natural fertilizer in the soil—a process called nitrogen fixation. This is a time-tested agricultural principle; research materials I’ve reviewed even note a similar concept was used in ancient China with rice crops to improve fertility.
Plants to Avoid: 5 Foes for Your Kale Patch
Just as important as knowing what to plant is knowing what not to plant with kale. The importance of this is not a new idea; I was fascinated to read in a Utah State University article that even the ancient Romans had observed some plant pairings were detrimental. Planting these foes next to your kale can lead to stunted growth, increased pest pressure, and disease.
- Other Brassicas (e.g., Broccoli, Cabbage, Cauliflower) This is the most important rule, and it operates on two timelines. Firstly, don’t plant members of the same family together in the same season. This is like opening a massive, all-you-can-eat buffet for the same pests (like cabbage worms) and soil-borne diseases (like clubroot). Secondly, and just as critically, is the principle of crop rotation. Research from universities like Cornell and the University of Minnesota strongly advises that you do not plant any brassica crop in the same patch of soil more than once every three to four years. This is the single most effective way to break the life cycles of persistent pests and diseases.
- Strawberries This was a surprising discovery in my research. While they don’t directly compete for the same nutrients, strawberries are a major magnet for slugs. Since slugs also adore tender kale leaves, planting them near each other is asking for trouble.
- Tomatoes and Peppers These nightshades are very heavy feeders and can compete directly with kale for key nutrients in the soil, potentially stunting its growth. While some experienced gardeners have success separating them with other plants, I don’t recommend it for beginners.
- Fennel & Sunflowers I group these two together because they present a similar, hidden challenge. Both are known to be allelopathic, a scientific term for plants that release biochemicals into the environment that can inhibit the growth of their neighbors. Fennel is famously unfriendly to most garden plants, while sunflowers can cast excessive shade in addition to their allelopathic effects. It’s best to give both their own dedicated space, far from your kale patch.
Smart Layouts: Spacing Your Kale and Its Companions
As I emphasize in my main How to Grow Kale guide, even when you’re adding companions, it’s crucial to respect the proper spacing for your kale. Giving each kale plant about 18-24 inches of space ensures good airflow, which is key to preventing fungal diseases.
I recommend a strategy of “interplanting” where you place companion plants like onions or garlic in the spaces between your kale plants, and a strategy of “border planting” where you create a protective barrier of aromatic herbs or marigolds around the entire bed.
Frequently Asked Questions (FAQ)
Conclusion: Your Garden is an Ecosystem
Thinking about your garden as a community of interconnected plants completely changed my approach to gardening. By choosing the right companions for your kale, you can solve problems before they even start, leading to a healthier, more organic, and more abundant harvest.
You have now mastered the art of building a strong, supportive community around your kale plants. The final step is to ensure the kale itself is as healthy and productive as possible. For my complete, step-by-step guidance on perfect soil, watering schedules, and the “cut-and-come-again” harvesting method, it’s time to visit the main guide.
-> Read My Complete Guide: How to Grow Kale from Seed to Harvest
