Companion Planting: Cracking the Code

Have you ever looked at lists of companion plants and wondered why? Why are these certain plants good companions? What makes them go well together? And most importantly, is there a way to implement companion planting without cross referencing lists in multiple books and websites? The answer is yes, you can gain a deeper understanding of companion planting, and this will make it easier and quicker for you to plan vegetable garden layouts.

Companion planting in the vegetable garden is essentially a way of mimicking nature on a small scale. Every cultivated variety of fruit and vegetable has a wild ancestry and at one point, grew happily with no interference from humans. Each plant has different preferences when it comes to habitat.

To master the art of companion planting, you will need to understand why certain plants grow well together and others don’t. To simplify this concept to its core, companion plants:

  1. Have similar preferences in growing conditions. Or,
  2. Provide for the needs of other plants. And,
  3. Don’t compete with one another for light, nutrients, etc.

How can plants help one another?

Permaculture principles teach us to “integrate rather than segregate”. Intensive gardening with companion plants is a great way to achieve this goal. There are several benefits certain plants provide that can be advantageous to their neighbors.

The Vegetable Gardener’s Guide to Permaculture has some great charts that explain exactly which “dynamic accumulators” (plants that draw up and collect soil nutrients from deep within the soil) catch which nutrients (nitrogen, calcium, potassium, etc). I highly recommended this book for anyone wishing to understand companion planting and permaculture design in a more profound way.

The most important aspects of a plant’s productivity are soil, water, light, nutrients, shelter, pollination and pest/disease resistance. Certain plant families (learn 11 plant families here) are known for their ability to enhance these aspects for other plants.

Borage is a wonderful companion plant but self-seeds profusely. It has a mild cucumber-like flavor and it’s edible flowers attract pollinators. As a cover crop it can be used for green manure to add nitrogen to the soil.

Accumulate Soil Nutrients

Healthy soil is key to productive plants. Some plants such as beans, chives, collards, marigolds, borage, comfrey, clover, lamb’s quarters, licorice, chamomile, yarrow, sunflower, and primrose help to build healthy soil and fix nutrient deficiencies from plants that are heavy feeders.

You must first determine what kind of soil you have before determining how to improve it. You can use a soil test meter or get a test kit to gain a deeper understanding of your soil composition.

Soil Composition

The type of soil present can be a factor to consider as well. Some plants grow best in sandy soil – root vegetables, lettuce/greens, the nightshade family, squash and strawberries to name a few. If you were to plant carrots in rocky soil, for example, you would end up with deformed roots that were forced to grow around the obstructions.

Potatoes prefer loose soil with good drainage. Rocky soil can damage the root crops and waterlogged soil can cause the potatoes to rot and mold.

Vegetables in the cabbage family, as well as beans and peas, perform well in clay soil due to its ability to hold water and nutrients. However, this sometimes waterlogged soil can cause root rot on more sensitive plants like berry bushes and spring vegetables. So now it is clear why plants like cabbage and strawberries jus don’t go well together. They thrive in different soil conditions.

There is also soil PH to take into account. Certain plants like blueberries, carrots, cauliflower, celery, cucumbers, garlic, sweet peppers, pumpkins, winter squash and tomatoes prefer more acidic soil. These plants do well planted in the same area since they have the same needs. Plants that prefer alkaline soil may not perform as well when planted together with acid loving crops.


Some plants can act as a ground cover to help retain moisture in the soil, suppress weeds and prevent soil from being washed away. These are known as “living mulch” or “cover crops”. Sprawling vine plants like squash, sweet potatoes, strawberries, or gourds can cover the earth and slow the process of water evaporation. Low growing herbs like thyme can be planted between taller plants to keep weeds from growing there.

Zucchini and other squash have broad leaves that shade the soil to prevent water from evaporating and suppress weed growth.

There is also the “chop and drop” mulch method where plants such as comfrey, borage, legumes or clover are cut down and left in place to mulch the area. This is often referred to as “green manure”. The decomposing plant material continues to boost the soil by leeching nutrients just as it would in a compost pile.

Pest Control and Pollination

Produce can be decimated by pest insects, but with the proper employment of companion plants, the insect population can be controlled. The same techniques can be used to deter animal pests.

Plants in the onion family are great for camouflaging the scent of more savory garden plants. Flowering herbs attract predatory pollinators which in turn reduces the pest insect population. The aster, mustard, and carrot plant families are all stars when it comes to attracting beneficial insects.

Nasturtiums come in different colors and sizes including both bush and vine varieties

Calendula (pot marigold) and nasturtium are great companions for most garden veggies. They repel pests and attract pollinators with their beautiful flowers that are both edible and medicinal. I use them to create borders around my raised beds which adds both beauty and function.


It benefits plants to be grouped according to water requirements. How quickly the soil drains has a lot of impact here too. Some plants like melons, squash, corn, green beans, sweet potatoes, okra, peppers and eggplant like growing conditions that are hot and dry. Even though they need plenty of water, they like to dry out in between and enjoy full sun.

You wouldn’t want to pair these plants with those that like moist conditions such as celery, lettuce, cabbage, broccoli, cauliflower, brussel sprouts or asparagus.

Sun, Shade and Shelter

When designing your companion garden, analyze your site’s sun path and weather conditions. Take note of how many hours of light different locations receive. Use tall, bushy plants to protect tender shade loving greens from being scorched by the sun or ravaged by strong winds.

Plants with thorns or irritating hairs can be placed around more defenseless neighbors to protect them from hungry animals. Raspberries, blackberries, squash vines, and stinging nettles are great options for sheltering plants that are plagued by critters like corn, carrots, leafy greens, strawberries, peas, and broccoli.

Living Trellis

Pair vine plants with fast growing tall annuals to create living trellises. Just be sure your trellis plants are strong enough to support the weight of the fruit produced on the vines. Corn, okra, sunflowers, Jerusalem artichokes, amaranth, orach and sorghum are great options to use as living trellises. When these plants begin to grow, plant climbing vines such as peas, pole beans, malabar spinach, nasturtiums, small squash/melons and hops next to them.

Okra grows tall very quickly and is a great living trellis for vine plants like green beans.

Spacing and Size

Some plants may get along if it weren’t for their size. Large bushy plants like tomatoes or sprawling vines like watermelon grow quickly and can overshadow or choke out neighboring plants. Check out my post Unlock the Secrets to a Perfect Garden Layout for a helpful plant spacing guide.

You wouldn’t want to plant vine cucumbers around peppers, for example, the slower growing pepper plants need full sun and would be climbed and overtaken by the cucumbers. Sunflowers, however, would be a great companion for the cucumbers because they grow tall very quickly and could act as a living trellis.

Perennials vs Annuals

When designing your planting layout, consider grouping perennial fruits and vegetables together for a “no work” garden. This will help preserve the root systems of the perennial plants and continue to build healthy soil.

Take into account perennial vegetables like Jerusalem artichokes or sweet potatoes which require digging to harvest the tubers or roots. These types of plants should be planted with annuals that won’t suffer from root disturbances.

Companion Planting: Wild raised beds

Some annuals like cilantro, dill, radishes, parsnips, borage and lettuce will reseed themselves vigorously and come back like weeds, so I usually treat these types of plants as perennials and let them come back on their own every season. For this reason, reseeding annuals do well in perennial beds or forest gardens.

Practical Knowledge

Until you get comfortable assessing these factors of compatibility in your garden plants, it is helpful to cross reference a comprehensive list of companion plants. But as you practice companion planting in your garden, the designs will quickly become like second nature.

To see examples of plants that work well together, check out my Raised Bed Vegetable Garden Plan. I have more than 15 beds with multiple combinations of companion plants already designed.

To help you layout your vegetable garden design, I have created this Garden Design and Planning Tool. You may also want to learn How to Make a Succession Garden Schedule to go hand and hand with your companion planting designs.

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