Companion Planting for Cannabis: What to Grow With (and What to Avoid)

Companion planting is the practice of planting a diverse range of crops together for a multifaceted approach to enhancing your garden’s resilience. When it comes to companion planting with cannabis, there are a few key things to be aware of. Various plants serve different purposes in your garden, from pest control by repelling insects or attracting beneficial predatory insects, to enhancing soil health and increasing terpenes, ultimately improving overall plant health.

Benefits of Companion Planting for Cannabis

Companion planting works by leveraging the interactions between plants above and below ground. For cannabis growers, the benefits of companion planting include:

• Natural pest control
• Plants that repel pests and deter pests
• Increased populations of beneficial insects
• Improved soil structure and biology
• Nitrogen-fixing plants that feed the soil
• Reduced water loss through living ground cover
• Increased terpene synthesis through microbial and plant communication

When done correctly, cannabis companion plants support the entire garden ecosystem, not just the cannabis plants themselves.

How Companion Plants Support Cannabis

In nature, biodiversity is the key to a thriving ecosystem, and your garden is no different. Each plant contributes its own benefits and serves the garden in various ways, from root system interactions to volatile compounds that repel pests and improve plant health, to providing habitat and food for beneficial insects, living mulch that reduces water evaporation, and enhanced soil health.

Volatile Organic Compounds

Every plant produces different terpenes and root exudates that communicate with one another and with various microorganisms. These microbes are your plants’ first line of defense when it comes to fighting off pathogens like powdery mildew, fusarium, or septoria. These terpenes are just one type of volatile organic compound (VOC) produced by plants, serving multiple purposes.

Some VOCs produced by plants can enhance the levels of terpenes and plant hormones in neighboring plants, simply by their presence. While some scents actively repel pests, others attract beneficial insects.

Attracting Beneficial Insects

One of the best services that companion plants provide is attracting beneficial insects. As previously mentioned, certain plants attract these types of predatory insects that feed on pests simply by their scent. However, the main reason beneficials are attracted is that they provide nectar as food and a breeding habitat. Instead of buying ladybugs or praying mantises, you can build them a home and keep them around long-term.

Cover Crop (aka Living Mulch) and Reducing Water Evaporation

Cover crop, also known as living mulch, reduces evaporation by altering the interaction between heat, light, and air at the soil surface. Bare, dark soil absorbs sunlight, heats up quickly, and loses water rapidly through evaporation. When the soil is covered with living plants, the green canopy reflects and diffuses sunlight, shading the soil and keeping it cooler.

Living mulch also slows wind at ground level, trapping humid air near the soil surface and further reducing moisture loss. Together, cooler temperatures, reduced direct sunlight, and limited airflow help retain more water in the soil for longer.

Enhanced Soil Health

Companion planting improves soil health by increasing microbial diversity and improving soil structure. The more root exudates present in the soil, the greater the microbial diversity and activity. This means that nutrients are cycling more effectively and become more available to plants, while the soil structure also improves.

These same microbes that are enhancing your plant’s health are feeding your plants and, while doing so, creating microbial slime that produces aggregates within the soil. Soil aggregates enhance structure by improving porosity and water flow, which in turn facilitates nutrient uptake and effective water management.

Certain plants increase nutrient availability by either extracting them from the soil or drawing nitrogen from the air. These plants can be utilized in compost, fermented plant extracts, or tilled back into the soil.

Best Companion Plants for Cannabis

1. Companion Plants That Attract Beneficial Insects

Beneficial insects are one of the most effective forms of biological pest control for cannabis. These plants provide nectar, pollen, and habitat for predators that feed on common cannabis pests.

Great companion plants include:

• Yarrow
• Dill
• Fennel
• Calendula
• Alyssum
• Buckwheat

Why they work:

• Each plant attracts a different beneficial insect
• Supports lacewings, lady beetles, hover flies, and parasitic wasps
• Reduces the need for sprays, especially during the flower phase

Calendula flowers

These are some of the most reliable marijuana companion plants for outdoor and greenhouse grows.

2. Companion Plants That Repel Pests

Some plants release aromatic compounds that naturally repel pests or disrupt their ability to locate cannabis.

Best options:

• Basil
• Chives
• Garlic
• Onions
• Lemon balm

Lemon balm is a particularly great companion plant because it is fast-growing, highly aromatic, and helps deter cabbage moths while improving garden biodiversity.

Tip: Use aromatic plants as borders or nearby companions, not overcrowded in containers.

3. Companion Plants That Improve Soil & Root Health

Healthy soil is the foundation of healthy cannabis plants. These companion plants improve soil structure, feed microbes, and support nutrient cycling.

Top soil-building companions:

• • Clover (white or crimson)
  • Alfalfa
  • Vetch
  • Lupine

• Comfrey

• Buckwheat

Buckwheat serves as a natural hydrometer on many outdoor commercial farms in Northern California.

Many of these species are nitrogen-fixing, meaning they convert atmospheric nitrogen into forms that are plant-available, a significant benefit for long-term soil fertility. They also create fibrous root systems that protect soil structure and prevent erosion. Clover should be planted as a cover crop, as it can attract spider mites.

Comfrey and buckwheat are not nitrogen-fixing, but are known for pulling nutrients out of the soil that other plants can’t. When you chop and drop these plants, meaning you cut them and leave them to decay on the soil surface, they feed microbes and release those nutrients, making them available for your cannabis plants to consume.

4. Companion Plants With Deep Root Systems

Plants with a deep root or taproot help break compacted soil layers and bring minerals closer to the surface. These plants are best suited for use around borders and walkways with heavy traffic, as they help reduce compaction and improve water flow.

Best choices:

• Comfrey
• Chicory
• Dandelion
• Daikon or Tillage Radish

Comfrey is a favorite plant for cannabis gardens because it:

• Mines potassium and calcium
• Improves soil tilth
• Can be chopped and dropped as mulch
• Turned into fermented plant extract

Be careful when planting comfrey, as it is nearly impossible to remove once it is established. For this reason, consider using the Bocking 14 variety, which is sterile but can reproduce through root cuttings.

5. Companion Plants That Reduce Water Usage

Cover crops help reduce evaporation, buffer soil temperature, and improve water infiltration. It’s especially valuable for outdoor cannabis.

Best cover crop options:

• White clover
• Creeping thyme
• Strawberries (in some systems)

A low-growing cover crop can significantly reduce watering needs while supporting beneficial soil microbes.

Companion Plants That Can Support Terpene Production (JA Signaling)

Some companion plants don’t add terpenes directly, but they can influence jasmonic acid (JA) signaling, a plant defense pathway involved in terpene and secondary metabolite production. Aromatic plants and certain soil companions can release volatile compounds or create mild, beneficial stress that primes cannabis for stronger terpene expression.

Companion plants that may support JA signaling include:

• Basil
• Rosemary
• Sage
• Lemon balm
• Yarrow
• Clover (via root-mediated signaling and competition)
• Comfrey (Bocking 14)

Yarrow flowers

These plants are best used as borders or nearby companions, where they can influence plant signaling without competing heavily in the cannabis root zone.

Bad Companion Plants for Cannabis (Plants to Avoid)

Not all plants play well with cannabis. Some compete aggressively, attract pests, or interfere with nutrient availability.

Worst Companion Plants for Cannabis

Brassicas (cabbage, broccoli, kale)

• Heavy feeders
• Compete for nitrogen
• Can attract aphids and caterpillars

Corn

• Tall and competitive
• Attracts pests like corn borers and aphids
• Creates airflow issues

Sunflowers

• Aggressive root system
• Allelopathic compounds may inhibit nearby growth
• Heavy nutrient demand

Mint (in-ground)

• Extremely aggressive spreader
• Competes for water and nutrients
• Better kept in containers only

Large woody perennials

• Shade cannabis plants
• Compete heavily for water
• Disrupt spacing and airflow

Understanding the worst companion plants for cannabis is just as important as knowing the best.

Companion Planting Tips for Cannabis Growers

• Choose fast-growing companions for early protection
• Avoid overcrowding (airflow matters)
• Use companions as borders, not replacements for spacing
• Match water needs between cannabis plants and companions
• Observe and adjust (every garden is different)

The best companion plants for weed are those that complement your growing style, climate, and soil.

Choosing the Right Cannabis Companion Plants

Companion planting isn’t about perfection. It’s about stacking small advantages that add up to healthier plants and fewer problems. When chosen intentionally, companion plants can enhance soil health, mitigate pest pressure, attract beneficial insects, and foster resilient cannabis gardens. Start simple, focus on soil health, and let observation guide your choices.

FAQ

What are the best companion plants for cannabis?

The best companion plants for cannabis include buckwheat, lemon balm, comfrey (Bocking 14), daikon radish, and sweet alyssum. These plants improve soil, attract beneficial insects, repel pests, and can support terpene production in your cannabis garden.

What companion plants are best pest control?

To help with pest management, grow aromatic herbs like basil, lemon balm, sage, and flowering plants like buckwheat near your cannabis. They attract beneficial insects such as ladybugs and lacewings and can naturally deter pests like aphids and spider mites.

Can companion plants improve soil or nutrient availability?

Yes. Deep-rooted, nitrogen-fixing companion plants like comfrey and clover enhance soil structure, increase nutrient availability, and improve water retention, thereby creating a healthier environment for cannabis growth.

What are the worst companion plants for cannabis?

Avoid aggressive or nutrient-heavy plants, such as brassicas (cabbage, broccoli), sunflowers, and mint (in-ground), as well as large woody perennials. These plants compete for water, nutrients, and light and may attract unwanted pests.