How to Choose, Plant, and Grow Companion Plants (6 Steps)

Some of my friends and family want to get into companion planting, and they weren’t quite sure where to start. I’ve been learning about and experimenting with companion plants for over two years now, and I’m still just as excited as I was when I started. So, I put together a guide for my friends and family. Here’s the complete resource I provided them.

Start companion planting by first checking your climate and soil. From there, select your plant pairings and identify the best location and spacing. After planting, build the soil with compost and mulch, and apply fertilizer if you’d like. Aim to grow more annuals until the perennials come into maturity.

So, to recap, here are the six steps of companion planting:

1. Consider your climate
2. Check your soil type
3. Select plant pairings
4. Identify the ideal location (and plant)
5. Build soil with compost and mulch
6. Apply fertilizer (optional)

Now, to help you start and grow a thriving companion planting garden, let’s take a look at each one of these steps in more detail.

1. Consider Your Climate

Before you choose the companion plants you’d like to grow, I’ve learned from past experience it’s best to first check your climate and soil type. So, if you’re on board, let’s start with climate.

When addressing your garden’s climate, we’re looking at three main aspects: sunlight, rainfall, and temperature.

Sunlight

Similar to how sunlight is essential for us to obtain vitamin D, it’s also essential for plants. Without sufficient sunlight, plants have a difficult time absorbing nutrients, maintaining their immune system, and producing leaves, flowers, and fruit.

According to professional forester Peter Wohlleben in his book The Hidden Life of Trees, the majority of plants process sunlight by using the top side of their leaves similar to a solar panel, while the bottom side is used to transpire and respirate—breathing in carbon dioxide and exhaling moisture and oxygen (the reverse of how most animals breathe).

Normally, most plants require at least six hours of direct sunlight daily to reach the top side of their leaves. This amount is necessary for plants to properly photosynthesize, which is their main form of obtaining energy in the form of sugars.

These sugars are also partly secreted through their roots to feed beneficial soil life such as mycorrhizal fungi in exchange for extra nutrients.

Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.

Department of Biology, University of Fribourg, Switzerland

However, too much sunlight or heat can also be a bad thing—it can result in scorched leaves and drought stress. Sensitive plants like avocado trees are especially susceptible to drought stress, commonly resulting in leaves drooping and browning.

Fortunately, drought stress can be mostly minimized by providing partial shade, compost, and mulch (more on these practices later).

Since every plant has its own sunlight requirements (full shade, partial shade, or full sun), there’s no golden rule of sunlight to provide your entire garden. Six hours of daily sunlight is the best general “rule”, but this also depends on the plant’s heat tolerance.

Once you know how much sunlight and heat each plant prefers, position them in the garden or pasture in a way to provide it to them. Also consider using other, taller plants as partial shade for the smaller, more heat-sensitive ones.

Keep in mind that the position and duration of sunlight change with the seasons, so plan accordingly.

Action Step: Check your garden’s sun exposure as well as the amount suggested for the plants you’re considering. After planting, observe the plant over time to see if you need to adjust its sunlight levels.

Rainfall

One benefit of selecting plants that are native to your area is that they’ve already been proven to survive fairly well on their own. While sunlight and temperature are two parts of this, rainfall is another important component.

The average rainfall in the US in 2020 was 30.28 inches (source), which is enough for many established plants.

However, plants that are not yet mature or not native to dry regions typically require supplemental water.

If you find that you do need to provide supplemental water, the best way to do so is by first checking the soil’s moisture. This is also the most optimal way to prevent both over and under-watering. A good trick to check your soil’s moisture is by pushing a finger into the top 2-4 inches of soil.

Simply put, if the soil is dry, water it. If it’s wet, wait for the soil to dry before watering.

However, watering becomes more complex if the soil has poor drainage (more on this soon).

Action Step: Before selecting your companion plants, compare what your average rainfall is in your region to the needs of the plants you’re considering. Also, think about how you’d provide supplemental water if needed (using a garden hose, providing drip irrigation, capturing rainfall, etc.)

Temperature

When I first got into gardening, I kept hearing things like 7b and 9a and I had absolutely no idea what people were talking about.

I later found out that these hardiness zones were created by the USDA in 1960, which conveys the average minimum temperature in any given area (source). Because of this resource, it became easier for gardeners to know if citrus trees or other frost-sensitive plants would survive in their region.

For example, at the time of this writing, I’m living in Austin, Texas. The hardiness zone here is 8b, which means our winters are an average low of 15 to 20ºF, which is just below the cut-off for growing citrus trees (typically requiring zones 9-11). 

However, no matter your hardiness zone, there are methods to stretch it. These methods commonly include moving potted plants indoors during the winter, growing in greenhouses, and establishing microclimates.

Action Step: If you haven’t already, find out what your region’s hardiness zone is and identify 10 plants that work best in that zone and that you’d be interested in growing. Oftentimes, you can find these plants by searching for plants native to your area.

2. Check Your Soil Type

Moving onto soil, there are three types, all with different advantages and disadvantages.

Soil Type	Pros	Cons
Sand	Good drainage	Does not hold nutrients well
Silt	Holds nutrients well	Poor drainage
Clay	Holds the most nutrients	Even worse drainage than silt

Ideally, the soil should have a mix of sand, clay, and silt, also called loam. Properly balanced soil provides plants with sufficient nutrients, drainage, pH, and root space.

Most plants require their soil to be:

• Rich in organic matter
• Loose
• Well-draining
• 5.5-7.0 pH

Generally, hitting all of these markers means providing slightly sandy, loam soil.

The reason behind this is that while clay has an alkaline pH, sand is acidic and dissolves the solid nutrients in the soil, making them more accessible to be absorbed by the plant’s finer roots (source).

However, too little or too much of any soil type can pose problems including poor drainage or leaching nutrients. This is why purchasing reputable brands of potting soil or making your own is helpful (I personally like to mix equal parts of sand, peat moss, perlite, and compost).

You can find out if your garden’s soil drains well by digging a 1-foot by 1-foot hole and filling it with water. If the hole drains slower than 2 inches per hour, it has poor drainage.

Typically, it’s difficult to amend garden soil due to the volume of amendments needed. This is why building a mound of soil on top of the ground is useful when planting in poor soils. Over the long run, you can also provide layers of compost and mulch on top of your garden’s soil, which break down into smaller pieces, working their way into it. With enough time, the soil will amend itself.

If you have livestock, using manure or pasture rotation are two more ways to accelerate amending soil.

Action Step: Use a pH strip or meter to test your soil’s pH. Test drainage by using the hole test mentioned above. If your soil has either poor pH or drainage, consider planting in mounds of soil or raised beds until the amendments naturally build the soil over time. You can see which pH meter I use by visiting my recommended tools page.

3. Select Plant Pairings

Healthy forests have different vertical layers and sizes of plants. Trees, shrubs, grass, weeds, vines, and more all contribute as parts of a whole.

While each of these plants competes for sunlight, the end result is that the sun rarely touches the forest floor. This is a huge benefit as the more sunlight captured by the plants, the more biomass, food, and life the forest can sustain. And this is also true for companion plants and food forests.

In a food forest, each companion plant should not only be chosen on what it provides you and its adjacent plants but where it sits in the overall system.

Along with maximizing the capture of sunlight, other functions of a food forest include holding groundwater via roots, adding nutrients to the soil from fallen leaves and branches, and promoting transpiration and shade from canopies.

By growing in this layered system, these plants create their own microclimate—partially independent of the climate of the surrounding area.

This practice of companion planting has long been proven by nature but now it’s recently proven by gardeners and other plant professionals. As a result, this layered approach is being widely adopted, and WAVES of backyard gardeners are creating their own food forests in their backyards.

James Prigeroni, Marisha Auerbach, and Andrew Millison are just a few examples of those who have completely transformed their backyards to provide an abundance of habitat, food, and more.

However, you can of course plant companion plants in your backyard without making a food forest. You’ll likely find it’s still more than worth the time and investment. In this case, aim for only one connection to be made between plants. For example, planting wildflowers to boost your apple tree’s pollination.

To see more companion flowers, check out my other post: The Top 10 Companion Flowers for Gardens, Vegetables, & More.

The rest of this section is focused on the different vertical layers of food forests, so feel free to skip to section 4-Ideal Location and Planting.

For those who are looking to grow a food forest, let’s take a closer look at the six different layers.

• Overstory
• Midstory
• Understory
• Ground Cover
• Vines
• Swale

Overstory plants are the tallest and provide benefits such as partial shade, windbreaks, and mulch. They also have some of the largest root systems which allow for better drainage as well as holding more groundwater. 

Midstory plants are the next level and provide similar benefits, just at a smaller scale. 

Understory plants are typically more sensitive to the elements than the mid and overstory plants and grow well from their protection. 

Ground covers spread along the ground, shielding the soil and reducing evaporation. 

Vines fill in the gaps between the other plants, capturing the remaining sunlight before it reaches the ground. 

Swales are channels of still water that are designed to collect rainwater and promote groundwater seepage—growing the water table. Companion plants that are planted along swales protect the surface and groundwater, aid with ground penetration, and invite beneficial life such as frogs.

For a good resource on effective swale plants, check out this resource by Minnesota Pollution Control Agency.

So what do these different layers of plants look like in practice?

In tropical or subtropical climates such as Florida (zones 9-11), one could grow a collection of palm trees (overstory), banana plants (midstory), citrus trees (understory), sweet potatoes (ground cover), kiwi (vines), and comfrey (in swale).

In more temperate climates (zones 8 and below), grow oak (overstory), apples (midstory), blueberries (understory), strawberries (ground cover), grapes (vines), and vetch (in swale) together.

So, not only does each individual plant benefit its direct neighbor, but they also contribute to the others in the larger system.

Action Step: Identify three companion plants of each type (overstory, midstory, understory, etc.) that interest you. Feel free to borrow from the examples above. Don’t worry yet if they’re viable for your garden or not, we’ll get to that in the next chapter.

4. Identify the Ideal Location (and Plant)

Once you’ve checked your climate and soil, and selected your ideal companion plants, it’s time to look at spacing. Generally, herbs require about 4-6 inches each, shrubs 2-7 feet, and trees 15-25 feet (15 for dwarf and 25 for full-size trees).

However, spacing largely depends on the amount of sunlight and root space the plant needs. This is why checking your plant’s sunlight was the first step in this post.

For example, while citrus trees and banana plants are companion plants to each other, citrus trees require full sun and won’t grow well when planted directly under the shade of banana plants. Instead, plant citrus trees just outside of the drip line of the banana plant. This way both plants get full sun.

So, stagger your companion plants based on their desired amount of sunlight. But what about their roots—will they compete with each other?

Most plants don’t have invasive roots and typically don’t grow past their drip line, or canopy. However, some plants such as fig trees and avocado trees have invasive roots.

Because it’s difficult to tell which plants will have invasive roots, consider following these two methods:

1. Use SelecTree by Cal Poly
2. Observe the plants over time

SelecTree is an online tool made by California Polytechnic University that gives you a profile on many plants. One of the most helpful data points in the profile is the invasiveness of the plant’s roots. You can check out SelecTree by going to selectree.calpoly.edu.

The other step is to simply observe your garden over time. Even the most seasoned gardeners and permaculture designers don’t get their gardens right on the first try. Growing successful companion plant gardens and food forests requires repeated observation and iteration.

Once you’re ready to plant or move your plants, there are a few steps I like to keep in mind to make the move easier and reduce the chance of transplant shock.

1. Have the new ground (or pot) prepared
2. Remove as much of the plant’s current topsoil as possible, without damaging the shallow roots
3. Grab the base of the plant’s stem or trunk and lightly wiggle to free up some soil space
4. Using your other hand, scoop up and support the rootball
5. Lightly place the plant in the new ground (or pot) and fill it in with soil
6. Make sure the soil is at the same level on the stem or trunk as before
7. Water generously and add more soil as it compacts

If you’re growing your plants in pots or containers, repot them with fresh soil every 3-5 years. Typically, keep one companion plant per pot to avoid root competition and adequate sunlight. For growing multiple types of plants, larger containers such as raised beds are more suitable.

5. Build Soil With Compost and Mulch

After you’ve planted your companion plants, we’ll use the two best practices to provide them with nutrients while also keeping them protected from the elements.

Composting

Composting is the process of decomposing organic matter from beneficial bacteria, earthworms, and other soil life. Because compost recycles nutrients from other plants and organisms, it often has an abundant and complete nutrient profile required by most plants.

Compost also greatly improves the retention of soil moisture—with every 1% increase in soil richness holding 20,000 more gallons of water per acre (source). 

You can either choose to buy or make compost. Typically, compost that’s bought works well, but it can sometimes be older and the nutrients degrade over time. For this reason, fresh compost is best for most gardens.

When making your own compost, the three main methods are hot, cold, and vermicomposting. 

Hot composting is when the compost pile’s heat from decomposition is maintained between 135-160ºF. Cold composting is what it sounds like—composting at a cooler temperature. Lastly, vermicomposting is composting with a type of composting worm such as red wigglers.

While hot composting is the quickest to decompose, cold composting is the easiest. All you have to do to cold compost is throw food scraps and yard waste into a pile and let it decompose. That’s it! However, I would suggest putting at least a two-inch layer of dry dirt or carbon such as leaves, straw, or sawdust on top to prevent smells, mold, and flies.

Vermicomposting is in-between hot and cold composting as it’s faster than cold composting, but you don’t need to turn or maintain a high temperature as with hot composting. And you can even have a vermicompost bin in an apartment.

When I lived in an apartment, I got some red wigglers from the pet store, a bin from Target, and leaves from outside. After drilling holes in the bin’s lid for air, and placing leaves for the bedding, I simply added organic material like kitchen scraps to the bin and the worms did the rest! Every now and then I’d apply this compost to my garden and the plants absolutely LOVED it. After using it, new growth on the plants started almost immediately.

For more about making a worm bin in under 10-minutes and for under $50, see our video below.

Keep in mind that the nitrogen materials such as greens, coffee grounds, and yard waste needs to be balanced with carbon materials such as leaves, wood chips, or hay. This is called the carbon-nitrogen ratio. Too much or too little carbon or nitrogen results in problems with the compost. And this is true for all forms of compost.

According to Cornell University, the ideal carbon-nitrogen ratio of compost is 30:1 (source).

Normally, compost works well enough on its own, but it can be difficult to get in larger volumes. So, if you’re working with larger pastures, fresher manure might be the better option. There are some exceptions such as if you’re doing the deep litter method for your livestock and you have large deposits of compost (which includes decomposed manure and carbon materials).

Mulching

While compost adds valuable nutrients to the soil, mulch protects it. Without protection, the soil quickly dries out in the sun and wind, which is similar to holding a blow dryer to it. This is also a swift way to drought stress and kill plants.

When the soil does dry out, beneficial soil life such as earthworms and mycorrhizal fungi die off, further reducing the water and nutrient retaining qualities of healthy soil. This is why tilling is such a harmful practice—digging up the soil exposes the beneficial soil life to the elements, turning the living soil into dead dirt.

However, soil management practices such as composting and mulching promote healthy soils and revive dirt.

Mulch provides a sufficient ground cover for the soil, reducing evaporation and providing habitats and nutrients for beneficial insects and other small organisms. Mulching also reduces soil erosion—a larger issue than it seems and is affecting much of the US.

If you think about it, no one rakes leaves in the forest. The forest floor is almost always covered in layers of fallen leaves and branches. These materials build over time, providing quality compost and mulch in abundant quantities. So, don’t throw away your yard’s leaves or garden waste! The same can be said for kitchen scraps.

In my backyard, I collect fallen leaves and place them on top of the other plant’s soil as a mulch. This practice alone lowered my watering from once a day to about once a week. As mulch breaks down over time, it typically needs to be reapplied every 3-6 months.

6. Apply Fertilizer (Optional)

Synthetic vs Organic Fertilizers

While chemical fertilizers are helpful in the short term, they often have long term consequences such as killing beneficial soil life as well as pollinators. As a result, the nutrients, immune system, and natural yields of the plants are often affected.

Luckily, there are effective ways to fertilize gardens and pastures without the consequences.

According to the University of Massachusetts Amherst, both compost and manure contain all of the nutrients required by crops and pastures and are suitable to replace fertilizers (source).

This is why integrating livestock with cropland is becoming so popular. Not only does it fertilize the land incredibly well, but there are ZERO downsides when it’s properly managed.

But what about the smell of the manure? Isn’t it unsanitary to use on gardens or pastures?

In pastures, as long as you rotate your livestock’s pasture, the manure won’t build up and smell. Many permaculturists even recommended running chickens three days after the other, larger livestock. This way the chickens till the manure, eat the pests attracted to the manure, and add a bit of their own manure. It’s a win-win-win.

For more pest-repelling companion plants, visit my other post: 7 Companion Plants That Repel Pests

In gardens, you can buy compost with some manure in it, which is heat processed, leading to little to no smell. However, this can depend on the brand, so make sure to ask your local nursery to confirm if it smells or not. You can also use cold manure from rabbits or goats, although this should have some rest period as well.

Manure is the potent product of many plants and nutrients compacted into one nice little present of fertilizer.

Also, if you’d like to see more about synthetic vs organic fertilizers, check out my post: Is Manure Good for Fruit Trees (And Which Kinds Are Best)?.

In nature, a quick fix to one element usually means the decline of another. This is why we’re now at a tipping point with chemical fertilizers.

The good news is that building soil and changing the landscape compounds over time and usually begins to take off within 2-3 years.

If you’d still prefer to use store-bought fertilizers, there are a few tricks you can use to weed out the good from the bad fertilizers. You can see my fertilizer recommendations on my recommended fertilizer page.

To recap this post, when choosing plants for your companion plant garden or food forest, identify:

1. Your climate (and the plants’ preferred climate)
2. Your soil type (and the plants’ preferred soil)
3. Plant pairings (both individual and groups)
4. Ideal locations
5. Ways to naturally build soil
6. Proper fertilizers

For a bit of inspiration, I’ll leave you with one of my favorite companion planting and food forest videos.