How to Succeed with Companion Planting

Companion planting is a great tool to utilize in your dome greenhouse and your garden. The benefits are worth the time you invest in learning about this ancient method.

The companion planting method works by grouping plants together that will benefit each other, promote soil health, and enhance flavor. They also attract beneficial insects, provide shade and deter pests.

What are some examples of companion planting?

Tomato and basil are a great combination. Basil helps repel pests from your tomato plants.

It can also improve the taste of your tomatoes. It is interesting that plants we use together in recipes are wonderful companions in the garden.

Nasturtiums can act as a trap crop and lure pests away from your grapevine.

Did you know that borage will enhance the vigor and flavor of strawberries? Borage can also help keep those pesky cabbage worms away from kale!

Planting garlic around your potatoes will help protect them from pests with their pungent odor. Don’t forget it keeps vampires away!

What Is Companion Planting?

Companion planting is organizing your garden plan so that each plant has the greatest benefits. This is particularly important in a smaller greenhouse or garden space. Choose which plants are most important to you and then add companion plants that will help your chosen plants thrive. They can also improve the taste of some plants. This is an excellent method for a healthy garden.

How Does Companion Planting Work?

What this method does is help you use your space in the most efficient manner and enhance crop productivity. This ancient and organic technique is beneficial for your crops and your soil!

Let’s get into the science of why this works. Nature is diverse and that is why it works so well. Plants have a variety of needs and contribute in various ways to the habitat around them. Insects, wildlife and the soil all work together. In contrast, if we just grow one crop in our greenhouse, we are more susceptible to that crop failing due to predators or depleted soil.

Allelopathy

Allelopathy is a biological phenomenon where one organism produces biochemicals. These can impact germination, growth, and survival as well as reproduction of plants and other organisms. Known as allelochemicals, they can be beneficial (positive allelopathy) or detrimental (negative allelopathy) so it is wise to understand how they work in the garden.

For example, onions and carrots as companions. Onions have an issue with the maggots from the onion fly (Delia antigua). These maggots infest the bulbs and stems of onions and can destroy a whole crop. Carrots have problems with carrot flies (Chamaepsila rosae) that can attack the outer layers of carrots. However, onions have a chemical they give off that repels carrot flies and carrots have a chemical that onion flies don’t like. Such great companions for your garden!

Marigolds are another great example of an allelopathic plant. They release a chemical scent that actually reduces the reproduction capability of aphids (hooray!) which helps protect other plants from being destroyed by these pests.

Trap Crops

Trap crops are another method of integrated pest management. Insects are just like every other animal, they have food preferences. When their favorite food is not available, they will happily munch on whatever else they can find. So how does that help gardeners?

Add some attractive plants to lure pests away from your preferred crops. Once they fall for your trickery, simply remove the trap and dispose of it away from your dome!

Research by Lincoln University revealed that squash bugs, squash vine borers, spotted and striped cucumber beetles preferred Blue Hubbard squash. This helped farmers to control those four pests using Blue Hubbard as a trap crop. This also meant the farmers were using less fuel, labor and insecticides while protecting their cucurbits.

Nutrient Sharing

So what is nutrient sharing? Is it like a potluck? Does every plant bring something to the soil? Underneath your plants there is so much happening. And what is important to remember is that plants need a varied diet just like we do.

Before we discuss sharing nutrients, let’s look at what nutrients plants need. Plants need 17 different nutrients. Some of them come from water and air, but the other elements come from the soil. Plants send their roots down into the soil to tap into those nutrients, which are vital for growth. There are factors that play into plant growth, which include pH, temperature, organic matter and watering (or rainfall for outside gardening). This is why it’s important to test your soil to determine if it needs to be amended so your plants and their root system can thrive.

Nutrient sharing is when plants connect and share or transfer water, nitrogen, carbon and other minerals. The mycorrhizal network is made up of mycelium and that is how plants connect. They are tiny “threads” of the fungal organism that wrap around the roots of plants, connecting them and enabling them to share. This has been described as the “woodwide web” by German forester Peter Wohlleben.

When someone mentions fungus or fungi, most of us tend to think about mushrooms. Gardeners are happy when they see mushrooms because it indicates healthy plants. However, those mushrooms are the “fruit” of that fungus, so yes, be happy when you see them!

The Mycorrhizal Network

Nutrient sharing happens through these common mycorrhizal networks or CMNs. This happens through arbuscular mycorrhizal fungi. These wonderful networks are how plants can share nutrients and resources and contribute to the health of the ecosystem.

So another important consideration is which plants are placed in proximity with other plants. Will they be competing for nutrients or do they have similar needs? Basically, are they good companions? Do they have compatible soil, light and moisture needs?

History of Companion Planting

One of the earliest and best-known examples of companion planting is the Mohawk term “Kiohehkwen”, commonly known as the Three Sisters method. Kiohehkwen translates to “They give us life.”

Three Sisters companion planting was implemented by many Native American tribes. This method is to plant corn, beans and squash together. The Three Sisters work together as companions: beans fix the nitrogen in the soil and continuously supply it to the soil. Corn stalks provide a natural trellis for the beans to climb. Squash steps in to provide mulch as its broad leaves shade the soil. This reduces water evaporation and keeps the weeds down and helps to keep critters away.

The Three Sisters is not just a gardening method, it has a deep connection to Native American culture. Corn, beans, and squash were the staples in the Mohawk diet along with wild game, strawberries and maple sap. They literally were life to the Mohawk and were woven throughout mythology and have a spiritual connection.

Benefits of Companion Planting

1. Pest Control – Certain plants repel common garden pests. Some plants also act as “trap crops” to lure pests away from food crops.
2. Pollination –Herbs and flowers can attract pollinators to your greenhouse.
3. Improved Growth and Flavor – Some plant pairings enhance each other’s growth and flavor.
4. Efficient Space Utilization – Use vertical and intercropping methods to maximize your growing capacity. For example, tall vegetable crops can be used to protect smaller plants from harsh afternoon sun or as a natural trellis.
5. Soil Health and Nutrient Sharing – Nitrogen-fixing plants enrich the soil. It is also important to consider the positive impact of earthworms, fungi and good bacteria. Healthy soil produces healthy plants!
6. Weed Suppression – Ground covers such as oregano can help reduce weeds naturally.

Best Companion Planting Combinations

When inviting guests to your home or out to dinner, most of us consider personalities and how they get along so it’s an enjoyable time for all. Planning your garden is no different! Here are some favorite combinations to plant.

Vegetables

• Tomatoes and basil are a classic example of companion planting. Basil repels pests, but it also improves tomato flavor. Pasta anyone?
• Carrots and onions have a symphony of fragrance working together for each other. Onions have a chemical that repels carrot flies and carrots have a chemical that deters onion flies. This allows these two plants to grow together while their individual fragrances protect each other from insects.
• Beans and corn are one of the original companion plants. Beans fix nitrogen in the soil while corn provides a natural trellis for beans to climb.
• Garlic and potatoes also work well together due to garlic’s famous fragrance. While we may love the smell of garlic, it helps deter aphids, beetles and may also prevent blight.
• Carrots and tomatoes work well together because carrots need shade and tomatoes are heat loving. Since carrots prefer cool soil they will benefit from the shade the tall tomato plants provide. Carrots also act as an aerator in the soil, allowing tomato roots to drink deeply.

Flowers and Herbs for Pest Control

• Marigolds and tomatoes are always good together. Marigolds repel nematodes and other garden pests.
• Nasturtiums and cucumbers make good companions. Not only are nasturtiums beautiful, they are edible and deter aphids.
• Oregano and vegetables are another good combination. Oregano helps protect susceptible vegetables from sucking insects such as aphids. It also acts as a ground cover helping plants that prefer cooler soil
• Lavender helps cabbage thrive by repelling those horrid cabbage moths.
• Sage, Carrots and Cabbage are a winning combination as sage repels carrot flies and may repel cabbage moths.

Other companion planting methods are themed such as growing a “pizza” garden bed or growing a “salsa” garden bed! Have you grown either of these gardens? This year we have themed many of our on-site Growing Domes, we have a Salsa Dome, a Mediterranean Dome, an Asian themed dome, and even a rainbow dome (because you shouldn’t just taste the rainbow, you should eat it too!).

The Role of Pollinators in Greenhouse Gardening

Greenhouses can limit natural pollination— so how can you encourage it?

• One of our greenhouse options is the pollinator window for larger domes and our venting panels for smaller domes. This allows bees and butterflies to access the dome.
• Add a beehive to your outdoor garden. Honeybees need to be outside to experience temperature fluctuations so we do not recommend having a honeybee hive inside your dome.
• Grow flowers near your greenhouse and particularly near areas they can access the inside of your dome, such as doors and vents.
• It is also important to grow plants inside your greenhouse that are beneficial to pollinators. Some examples are catmint, peas, lemon balm, calendula, lavender, mint (best grown in a container), and echinacea.

Best Companion Plants for Attracting Pollinators

• Lavender and Borage – These plants draw bees and butterflies into the greenhouse. Plus they are edible as well as beautiful.
• Marigolds and Nasturtims – These plants attract pollinators and can also act as trap crops. Nasturtiums are also a nice addition to salads and can be used in other recipes.
• Cut Flowers – These are another option that attract pollinators, add beauty and may be an option for an agribusiness. There are so many options with cut flowers. Just remember to consider how much sunlight they need and soil moisture requirements when choosing which cut flowers to grow.

Tips for Pollination in a Greenhouse

• Keeping your dome vents open when possible will allow pollinators inside. If you have concerns about rodents or other intruders, you can add ¼” hardware cloth to allow beneficial insects access while keeping out larger critters. If you choose to install a pollinator window, paint the outside with flowers to attract them to the pollinator window. It’s a welcome sign in bee language! Plant flowers and pollinator-friendly plants both inside and outside near the pollinator window to guide pollinators in.
• Some plants may need help by hand-pollinating. For example, plants like cucumbers and squash may need help. Basically, any plants with different male and female flowers may need a bit of extra care.
• Consider adding some small bee-friendly habitats near the greenhouse entrance. Add small bee-friendly habitats near greenhouse entrances.

Plants That Should NOT Be Planted Together

Some plants do not work well together and should not be planted in close proximity. They may compete for nutrients, have different soil moisture needs, different light needs or impact the growth of other plants.

• Tomatoes and potatoes can be planted “near” each other, but planted too close to each other increases the risk of disease. They are in the same family and that means that they are susceptible to sharing the same diseases.
• Brassicas and tomatoes are both heavy feeders. This means that kale, cauliflower, broccoli and other brassicas will stunt your tomato plants growth with their voracious appetites.
• Onions and beans have issues with each other due to allelopathy. Onions release a chemical called allicin, which can inhibit the growth of neighboring plants, including beans.
• Mint and vegetables are not good companions for the simple reason that mint wants to take over the world and will conquer your vegetables.
• Blueberries and vegetables have different soil requirements which makes them poor companions. While blueberries need an acidic soil, vegetables prefer a more neutral pH. Blueberries, as long lived perennial plants, don’t like having their soil constantly disrupted.

Tips for Successful Companion Planting

• Crop rotation is important for nurturing healthy soil.
  • Crop rotation is planting crops in a different area of the garden rather than in the same location every year.
  • Planting the same crop in the same location every year can deplete the nutrients in the soil.
  • Rotating your crops to different locations helps maintain the soil’s health and helps prevent soilborne pests.
  • Alternating crops by choosing plants that fix nitrogen in the soil will improve the quality of the soil. Peas and other legumes are great options for fixing nitrogen.
  • Choose plants with shallow-roots one year and deep-roots another year. This will draw nutrients from varying depths of the soil.
• Plan your garden layout based on plant relationships and microclimates. It is important to know the microclimates in your greenhouse dome!
• Use companion planting charts as a reference. Here are a couple of options: Farmers Almanac Companion Planting Guide or The Spruce Companion Planting Chart.

Conclusion

Companion planting is a fun and creative way to experiment in your dome greenhouse. There are many varieties to try with plants so choose what you like the best. It’s a great way to let your creativity out with colors, textures and flavors!