In What's Wrong with My Marijuana Plant?: A Cannabis Grower's Visual Guide to Easy Diagnosis and Organic Remedies (Ten Speed Press, 2017) authors David Deardorff and Kathryn Wadsworth guide cannabis growers through questions and concerns they may have about growing healthy plants. Readers can use the images, graphs, and diagnoses in this guide to understand their marijuana plants better. Here, Deardorff and Wadsworth encourage gardeners to grow a polyculture environment, comprised of companion plants, to create a stronger and more diverse plant community for marijuana to thrive within.
Marijuana is an annual weed. In a single growing season, a seed-grown plant can grow to 12 feet (4 meters) tall before flowering, setting seeds, and dying. It’s a tough plant that grows in many parts of the world as feral hemp, where no humans provide it with sprays, fertilizers, supplemental water, or extra light. The specially bred modern strains with maximum THC and/or CBD may be somewhat more finicky than their wild cousins, but even these new varieties are hardy plants.
That said, if your plants are beset with problems and failing to thrive, a poor growing environment could be to blame. By giving plants the best growing conditions, you minimize stress and maximize yield. It’s good for cannabis, good for your pocketbook, and good for the planet.
Wild marijuana does so well on its own because of its inherent strength and its natural community. These communities are polycultures that feature high species diversity, structural complexity, and healthy, biologically active soil. These characteristics provide food, shelter, and reproductive sites for countless beneficial critters that help control pests and pathogens that may harm your plants. Mimicking healthy plant communities creates the best growing conditions and proves to be the best preventative measure and the most cost-effective way to keep plants healthy.
In a polyculture, lots of different kinds of plants grow adjacent to each other; in a monoculture, plants are all the same. In this case, that monoculture would consist of cannabis and nothing else, like a typical field of corn. By planting polycultures, you immediately create two important characteristics of natural plant communities: species diversity and complex structure. Choose plants from different families to establish species diversity. Choose plants that differ in height, width, rooting depth, flower color, and season of bloom to build complex structure.
Flowers and herbs are more than pretty faces and tasty treats. This diverse community, with varying structure, provides food and habitat for beneficial organisms. In addition, this community of plants lures useful predators, such as lady beetles, green lacewings, minute pirate bugs, and trichogramma wasps, to your crop. These predators seek out and destroy threatening pests. The habitat you create also offers a safe haven for beneficial fungi and bacteria, such as Trichoderma harzianum, Bacillus subtilis, and Pseudomonas fluorescens, that help protect your crop from pathogenic fungi and bacteria that cause diseases.
Best Companion Plants for a Polyculture
Several plants do the best job of attracting beneficial insects and creating a healthy polyculture environment. Choose those that work best in your climate and circumstances.
Asteraceae (sunflower family)
• Achillea millefolium, yarrow
• Aster species and hybrids, aster
• Baccharis species, baccharis
• Boltonia asteroides, boltonia
• Coreopsis species, tickseed
• Cosmos bipinnatus, cosmos
• Echinacea purpurea, purple coneflower
• Eupatorium perfoliatum, boneset
• Gaillardia aristata, blanketflower
• Helianthus annuus, sunflower
• Leucanthemum × superbum, Shasta daisy
• Ratibida pinnata, prairie coneflower
• Rudbeckia species, black-eyed Susan
• Solidago species, goldenrod
• Symphyotrichum species, hardy aster
• Tagetes species and hybrids, marigold
• Zinnia elegans and hybrids, zinnia
Apiaceae (carrot family)
• Ammi majus, laceflower or bishop’s weed
• Anethum graveolens, dill
• Angelica species, angelica
• Coriandrum sativum, cilantro or coriander
• Daucus carota, Queen Anne’s lace
• Foeniculum species, fennel
• Petroselinum crispum, parsley
• Zizia aptera, heartleaf Alexanders
• Zizia aurea, golden Alexanders
Lamiaceae (mint family)
• Nepeta × faassenii, catmint
• Ocimum basilicum, basil
• Origanum species, oregano
• Pycnanthemum species, mountain mint
• Rosmarinus officinalis, rosemary
• Salvia officinalis, culinary sage
• Thymus species, thyme
Other plant families
• Eriogonum species, native buckwheat
• Lobularia maritima, sweet alyssum
• Phacelia tanacetifolia, lacy phacelia
• Spiraea alba, meadowsweet
• Veronicastrum virginicum, Culver’s root
Create polycultures outdoors in the ground
To create polycultures outdoors in the ground, you can add one extra row of companion flowers and herbs per about five rows of marijuana and/or surround your patch with a border of beneficial flowers and herbs. Put beneficial flowers and herbs in the same row as your marijuana plants. In this case, select small, shallow-rooted plants (such as thyme, oregano, marigold, tickseed, Queen Anne’s lace, or cilantro) so that your marijuana does not have to compete for nutrients, sunlight, and water.
Create polycultures outdoors in containers
Do not plant flowers or herbs in the same pot as your marijuana. Cannabis is a heavy feeder and wants all the nutrients, sunlight, and water it can get. It will not be as productive if it has to compete with another plant for those resources in the restricted environment of a container. Instead, plant some extra pots with beneficial flowers and herbs, and place them next to your pots of marijuana plants. Shift pots around to find the best environment for each kind of plant.
Create polycultures indoors in containers
Indoors, you avoid many of the pests and pathogens that plague outdoor plots. However, even indoors your plants might be hosts to spider mites, aphids, scale, powdery mildew, gray mold, and other pests and diseases. Pests hitchhike into your grow room or greenhouse on your clothing or on your pets. They can also ride the breeze and float or fly through windows, vents, and doors. If you release any of the beneficial insects and mites covered in chapter eight to deal with these problems, put pots of flowers in the grow room or greenhouse to provide extra food and habitat for these beneficial creatures.
Reprinted from WHAT’S WRONG WITH MY MARIJUANA PLANT? Copyright (c) 2017 by David Deardorff and Kathryn Wadsworth. Published by Ten Speed Press, an imprint of Penguin Random House LLC.