Ask growers why they plant marigolds, nettles or garlic around their cannabis and you will hear about fewer pests, more ladybugs and, sometimes, better-smelling flowers. Some of those claims rest on solid agronomy. Others come from careful observation, and a few mostly from hope. This guide to companion plants for cannabis sorts them.
Our main practitioner source is Karla Avila of Flowerdaze Farm, a three-acre regenerative farm in Northern California’s Emerald Triangle. She described her companion planting in our interview with Flowerdaze Farm, and her quotations below come from it. What she reports is on-farm experience, not controlled trials.
At a Glance
| Plant | Claim or use | What the research shows |
|---|---|---|
| Marigold | Borders, against nematodes | Suppresses root-knot and lesion nematodes when grown densely before the crop; interplanting generally does not appear effective |
| Stinging nettle | Habitat for beneficial insects; ferment or tea as fertilizer | Nettle strips host aphid predators that also occur in nearby crops; fertilizer value not measured |
| Comfrey | A row a few feet from the cannabis | Avila’s on-farm observation only |
| Garlic and onions | Borders, as general pest deterrents | Pest-specific benefits in other crops |
| Basil, yarrow | Often named for better terpenes | No controlled terpene studies found |
What Is the Difference Between Cover Crops and Companion Plants?
The categories overlap. Cover crops can be grown before a cash crop, between cash crops or alongside one as a living mulch.[1] At Flowerdaze, Avila distinguishes them by timing and purpose: “Cover crops come before companion plants when ‘setting the stage’ in soil and fixing the elements that you want, especially nitrogen. Companion plants are planted alongside or in the vicinity of our commercial cannabis.”
In her system, cover crops build the soil (the subject of our guide to living soil), and companion plants share the season with the cannabis.
Where Does Flowerdaze Put Them?
Flowerdaze grows more than a hundred plant species around and between its cannabis, but keeps the important ones off the root zone: “Those that are really important we plant near the vicinity—not right at the base to give the cannabis root ball room to expand—but along the edges of the bed rows.” Marigolds, garlic and onions go on the borders; comfrey goes in its own row “a few feet away.” That is Avila’s approach, not a universal rule.
Which Companion Plants Work?
Marigold
“Marigolds pull nematodes towards their own roots and deter them away from cannabis roots,” Avila says. Marigold has the strongest research behind it of any companion plant, with one important qualifier.
Marigold roots release alpha-terthienyl, a compound that can reduce root-knot nematodes, but only while the roots are alive. French marigolds (Tagetes patula) work against the widest range of nematodes, mainly root-knot and lesion nematodes; Some marigold varieties can act as hosts for particular nematode species. University of Florida extension guidance states that intercropping marigolds with other crops does not appear to be effective. What works is growing them densely, where the crop will go, for at least two months before planting, every season, after testing which nematodes are present.[2] Border marigolds may earn their place for other reasons, but protecting the cannabis root zone from there is not what the research shows.
Stinging nettle
If Avila could keep only one companion, it would be nettle: “It deters pests and provides habitat for beneficial insects.” She also makes it into fertilizer: “If you have only one plant to make ferment/tea to feed cannabis all year round, it would be stinging nettle.”
The habitat claim has field support. Nettle strips beside pea, rapeseed and wheat fields held more aphid-eating predators than the crops, especially ladybirds.[3] A 2009 follow-up found that nettles and crops shared several of these species, including a ladybird, a hoverfly and a parasitic wasp, and that they usually appeared on the nettles first. The researchers concluded that the timing lets predators move between the two, though they did not track individual insects doing so.[4] The fertilizer claim is Avila’s practice, not a measured result; any ferment’s nutrient content depends on how it is made.
Comfrey
“We’ve done tests where the cannabis planted next to comfrey is the brightest green and the richest in chlorophyll,” Avila says. It is a farmer’s comparison without trial controls, but a testable one: compare leaf chlorophyll, growth and yield in otherwise similar rows with and without nearby comfrey.
Garlic and onions
Avila calls alliums “excellent pest management tools that deter all kinds of pests.” Research in other crops shows pest-specific benefits: in a two-season trial, canola grown in strips with garlic had the lowest cabbage aphid numbers of the intercrops tested.[5] No study establishes that alliums deter “all kinds of pests” in cannabis.
Do Companion Plants Bring in Beneficial Insects?
This is the heart of Avila’s pest control. “Our version of integrative pest management is this biodiverse ecosystem where when you build it, they will come,” she says. When hemp aphids arrived on the wind a few seasons back, “we saw insane amounts of ladybugs. They had habitat.”
The research leans her way. A 2020 global synthesis found that flower strips increased pest control in adjacent fields by 16% on average; hedgerows did not, and effects on yield were more variable.[6] Those studies are mostly beside food crops, not cannabis. They support habitat planting as a general principle, not guaranteed control of a particular cannabis pest.
Can Companion Plants Change Cannabis Terpenes?
This was the question the original version of this article asked, and nobody has shown it yet. Avila finds “that certain plants near cannabis help with terpene profiles,” and basil and yarrow are often named too. We found no controlled studies measuring cannabis terpenes with and without companion plants.
The idea is plausible: plants release terpenes and other volatile compounds that insects and neighboring plants can detect. But proving that a neighbor changes the terpenes in harvested flower would take a side-by-side trial with lab testing. A related but different experiment found no detectable hemp terpenes in grapes or wine from vines grown 68.5 feet away. That study addressed volatile transfer, not whether neighboring plants can change terpene production inside cannabis, and it was not peer reviewed.[7] For now, better terpenes are a reason to experiment, not an expected result.
How Should a Grower Try It?
- Build habitat first. Flowering borders have the strongest general evidence for improving biological pest control, while nettle strips have specific evidence that they host aphid predators.
- Treat nematodes before planting. Test the soil, then grow dense French marigolds where the crop will go for at least two months.
- Mind the root zone. Avila keeps companions off it.
- Test the rest. For comfrey or basil, compare similar plants with and without the companion, and keep the same notes on color, pests, yield and, if you can, terpenes tested at the same lab.
Companion planting is not cost-free. Poorly chosen plants can compete for water, nutrients and light; shelter unwanted pests; spread aggressively; or complicate sanitation and harvest. Stinging nettle is especially worth containing because it spreads through rhizomes and can interfere with workers.
As the original version of this article advised, keep a grow journal, and if a companion plant works in your grow, tell us. For the whole-farm picture, see our guide to regenerative cannabis farming and Karla Avila’s column on natural farming traditions.
References
- Kaspar TC, Singer JW. The use of cover crops to manage soil. In: Soil Management: Building a Stable Base for Agriculture. 2011:321–337.
- Krueger R, Dover KE, McSorley R, Wang K-H. Marigolds (Tagetes spp.) for nematode management. ENY-056. UF/IFAS Extension. Published 2007; revised 2016; reviewed 2024.
- Alhmedi A, Haubruge E, Bodson B, Francis F. Aphidophagous guilds on nettle (Urtica dioica) strips close to fields of green pea, rape and wheat. Insect Science. 2007;14:419–424.
- Alhmedi A, Haubruge E, Francis F. Effect of stinging nettle habitats on aphidophagous predators and parasitoids in wheat and green pea fields with special attention to the invader Harmonia axyridis Pallas (Coleoptera: Coccinellidae). Entomological Science. 2009;12(4):349–358.
- Mollaei M, Fathi SAA, Nouri-Ganbalani G, Hassanpour M, Golizadeh A. Effects of strip intercropping of canola with faba bean, field pea, garlic, or wheat on control of cabbage aphid and crop yield. Plant Protection Science. 2021;57(1):59–65.
- Albrecht M, Kleijn D, Williams NM, et al. The effectiveness of flower strips and hedgerows on pest control, pollination services and crop yield: a quantitative synthesis. Ecology Letters. 2020;23(10):1488–1498.
- Lupoi JS. Can cannabis terpenes alter wine grape chemistry? Terpenes and Testing Magazine. July 31, 2021. Reporting Sellu G, Kane M, Prendergast J, et al., Santa Rosa Junior College (not peer reviewed).
Editor’s note: This article was originally published on November 7, 2021, by Derek Johnson, as a short piece asking whether companion plants can enhance cannabis terpene profiles. In October 2026 the editors rebuilt it around Karla Avila’s companion-planting practice at Flowerdaze Farm and the research on marigolds, beneficial-insect habitat and terpenes. Quotations from Karla Avila are taken from our 2021 interview with Flowerdaze Farm.
Last updated October 2026 · Originally published November 7, 2021.
