Like humans and animals, plants love harmonious companionship! There are many plants (flowers, vegetables, herbs) which possess the ability to encourage or inhibit the growth of neighboring plants.
One way they accomplish this is by attracting or repelling harmful or beneficial insects (sort of like a garden soap opera). Some plants, especially herbs, act as natural insect repellents. They confuse insects with strong odors that mask the scent of the intended host plants. Dill and basil planted among tomatoes can protect from tomato hornworms. They can also regulate sun/shade, provide structural support, alter soil structure, and nutrient content, and inhibit weed growth ¹.
“Natural plant associations” are groups of plants that occur and live together in nature, mutually complementing each other. This could mean that a shade loving plant lives happily underneath a taller sun-lover, or that a deep rooted plant resides contentedly alongside a shallow-rooted friend. These plants don’t usually flower and fruit at the same times and often mature at different rates to maximize their light source.
Herbs may enhance or hinder the growth of their neighbors. For example, dandelion exhales ethylene gas, a hormone that promotes the premature ripening of fruits and fruiting of plants, inhibiting neighboring plant growth. Some herbs repel harmful insects by emitting aromas from their leaves or roots or aid fruit and vegetable plants by attracting otherwise harmful pest insects to themselves. Aromatic herbs like chamomile, chives, lavender, marjoram, parsley, sage, tarragon, thyme and yarrow enhance neighboring growth, repel pest insects, and attract butterflies and bees to your garden!
The active constituents and essential oil content can be increased in herbs by planting stinging nettle and yarrow in your herb garden. Peppermint’s essential oil is almost doubled when grown with stinging nettle! I think that is just amazing.
The following is a partial list of companion herbs/plants and short descriptions of their uses. Remember, when I say a plant “likes” another, it simply means it helps or is beneficial to its growth. This is a very broad subject and I am only brushing the surface! I hope that you will dive deeper on your own. If you are interested, Cornell University offers an extensive list online that you should see, found here.
I will also add that many herbs (mint family in particular) are invasive and will spread out pretty rapidly. Certainly do not let this prevent you from planting them. They are such a joy! I either plant them where I don’t mind them spreading, grow them in containers (you can still set them out near plants they will help), or create a strong, deep soil barrier (like a plastic underground corral) around their roots. Where there is a will, there is a way (for plants AND humans).
Alfalfa: Protects shallow rooting plants and is one of the few plants that actually grows well with Dandelion.
Anise: Seeds germinate and grow better alongside Coriander.
Basil: Really doesn’t like to grow near Rue! Likes tomatoes, peppers, oregano and asparagus.
Borage: Attracts lovely pollinating bees. Likes just about all plants; specifically aids strawberry, tomato and cucurbit growth. Borage flowers are just magical, really
Chamomile: Increases essential oil content of Peppermint when grown nearby. Likes Basil, onions, cucumbers and cabbage.
Celery: Mutually beneficial grown with tomatoes.
Chervil: Helps broccoli, lettuces and radishes.
Chives: Great under apple trees. It prevents apple scab! I have a sign under my apple tree so that my husband doesn’t forget and trim the chives. Also likes carrots, tomatoes, broccoli and cabbage.
Cilantro: Helps spinach.
Coriander: Hinders fennel seed formation. Attracts bees.
Dandelion: Exhales ethylene gas, inhibiting neighboring plant growth. I have another post on Dandelion. It’s one of my all time favorite and most beloved herbal allies!
Dill: Mature dill inhibits carrots. Likes cabbage, broccoli, corn, lettuces and asparagus.
Fennel: Inhibits dwarf beans and tomatoes.
French Marigold: Roots excrete a substance which kills nematodes. Likes tomatoes.
Garlic: Great companion for roses. Helps control potato and tomato blight. Garlic spray treats brown rot of stone fruit like peaches, plums, nectarines, apricots and cherries. Along with onions and shallots inhibits growth of peas and beans. Also likes cucumbers, peas, lettuces and celery.
Hyssop: Inhibits radish growth. Likes cabbage and increases grape yields when planted near grapevines.
Lavender: Attracts beneficial insects and aids general plant growth. Helps repel the codling moth which is major pests to agricultural crops (mainly fruits such as apples and pears), and the clothes moth, whose larvae feed on wool, feathers, fur, hair, leather, lint, dust, paper, and occasionally cotton, linen, silk, and synthetic fibers.
Lemon Balm: An all around beneficial herb, and is said to promote milk flow in cows when planted in their pasture/meadows. I’ve never tried that. For centuries Lemon Balm leaves have been crushed and rubbed inside a new bee hive to attract a swarm or encourage an existing swarm to stay. We do this and I can vouch for its efficacy. The smell of crushed Lemon Balm leaves is heavenly. It is an invasive mint family member but that does not deter me, as I have it planted in my yard and nothing would make me happier than for it to spread far and wide.
Marjoram: Likes peppers.
Mint: Repels cabbage butterfly caterpillars. Invasive.
Nasturtium: Helps to keep broccoli free from aphids. Great planted under apple trees to keep away woolly aphids.
Parsley: Great for roses and tomatoes.
Pennyroyal: Repels ants and protects against mosquitoes.
Peppermint: Protects cabbage from the white cabbage butterfly. Invasive.
Rosemary: Repels the carrot fly. Rosemary and Sage have a stimulating affect on each other. Also likes beans.
Roses: Aided by Garlic and Parsley.
Rue: Inhibits most neighboring plants, especially Basil. But it repels houseflies, so I keep some close to my house!
Sage: Also protects cabbages from the white cabbage butterfly and tends to make cabbages more tender.
Summer Savory: Beneficial to onions and green beans.
Spearmint: Repels ants and controls aphids on vegetables. Invasive.
Stinging Nettle: Very beneficial to neighboring plants by increasing essential oil yields and medicinal constituent contents. Just keep the little ones out of your nettle patch. It bites! Also invasive.
Tansy: Repels ants and flies. Tansy is also perfectly gorgeous. Invasive.
Tarragon: Generally beneficial for the whole garden.
Thyme: Repels the cabbage root fly.
Valerian: Attracts one of my favorite garden visitors, the earthworm!
Winter Savory: General insect repellent.
Wormwood: I haven’t personally had any trouble with it, but it’s known to inhibit the growth of neighboring plants. It also repels moths and helps protect cabbages from the .. you guessed it .. white cabbage butterfly.
Yarrow: Increases the aromatic quality of all herbs and enhances growth of neighboring plants.
This isn’t all of them, by any stretch, but it’s a good starting point. There are lots of books out there on companion planting and Amazon.com is a great place to find good, used (a.k.a. cheap) books, and they have plenty to choose from on this subject. The best way to utilize companion planting is to start with a general guide and experiment in your own garden. This method is invaluable for the organic garden and for defense against the 300+ insects in the world that are now resistant to an increasingly wide array of pesticides. More on natural pest control later…
References: ¹The Old Farmers Almanac, “Companion Planting Guide,” George and Becky Lohmiller,
Jackson County Master Gardener Manual and Entomology Guide (2008),
Alabama Cooperative Extension System Online,
Cornell Cooperative Extension Online, “Companion Planting” (1999)