10 Multipurpose Plants for Companion Planting

These companion crops are mutually beneficial, promoting overall plant and garden health.

field of alfalfa

Alfalfa's tender leaves are surprisingly nutritious, containing the entire spectrum of B vitamins.

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Usually when we talk about companion planting, we’re talking about planting flowers among our vegetables for their benefits—for example, planting marigolds among the vegetables to help deter aphids. On our farm, we’ve used this concept in our vegetable garden for years with varying levels of success. And while I love the beauty of flowers among my vegetables, a few years in I began to feel like I was missing something.

Companion planting is a crucial part of understanding how plants work, but our understanding of it is usually limited to which insect pests are repelled and which beneficial predators are attracted. In truth, the plant world is much like an iceberg—what we see above the ground is only a tiny portion of the immensity going on below our feet. Once we understand this fact of plant life, there is another aspect of companion planting we can harness.

Uses for Companion Crops

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Beneath the soil plants trade not only nutrients but also phytochemicals (the same plant chemicals we use for medicine). While trying to repopulate our forests with threatened native ginseng and goldenseal, growers with United Plant Savers quickly learned that, for success, they had to plant both together. Without their below-ground partnership, one plant was continually attacked by fungus, the other by animals. By sharing their chemical constituents in the surrounding soil, these plants are able to mutually protect one another. This is a relationship that is harnessed in permaculture, a garden design technique that makes use of the many complex and symbiotic relationships among plants, insects and animals.

Making use of all aspects of companion planting gives us the most vibrant plants and soils. Yet in our current model of companion planting, we often consider one plant the “main crop” (such as a tomato) and the other plant a supporting player (such as cosmos), whose sole purpose is to protect the main crop. The secondary plant is almost a throw-away. What a shame! Why not plant mutually beneficial crops together and give them equal attention in our kitchens or medicine cabinets? I love to grow multitaskers; especially in limited garden space, it’s important to choose only plants we can use in many ways. What follows are a few good examples to get you started.

1. Yarrow (Achillea millefolium)

In the Garden: The leaves of yarrow are used in biodynamic agriculture as a compost activator (the English herb writer Lesley Bremness wrote that even a single leaf will speed decomposition). It will also help draw beneficial insects to your garden—when planted in the neighborhood of your favorite plants, yarrow increases the aromatics of everything nearby and attracts predatory wasps, hoverflies and ladybugs. In the fall when the leaves decompose, they become a superb natural fertilizer.

In the Kitchen: While the leaves of this plant are bitter, I have seen a few recipes that make use of yarrow. This is a good candidate for salads, as it adds bitter flavors—believed to aid digestion and be beneficial to the liver—to the diet. Yarrow is somewhat similar to tarragon, and can be used where tarragon is called for. You might also mix yarrow with other delicately flavored herbs such as tarragon, chervil or parsley. Its flavor is destroyed by heat, so add it at the end of cooking or use it fresh.

In the Medicine Cabinet: Yarrow is an anti-inflammatory, as well as a fluid mover and a styptic (stops bleeding). While we can use it both topically and internally, I like it best as an external poultice to help reduce the swelling of sprains and strains. It’s commonly used as first aid for minor cuts and scrapes to reduce bleeding and for its antibacterial properties. The German Commission E recommends baths with yarrow to help relieve pelvic cramps; a strong yarrow tea can also be added to the bath to help reduce fever.

2. Borage (Borago officinalis)

In the Garden: Borage is my favorite companion for strawberries, squash and tomatoes, and in our orchard. An annual that hardily self-seeds, borage is said to strengthen any nearby plants. Perhaps this is because they tend to concentrate trace minerals in the soil. I love that they repel tomato hornworms and give my bees much to eat from early spring all the way through the first few frosts. Borage is also an excellent addition to the compost pile, as its leaves and stems contain calcium and potassium.

In the Kitchen: Borage is the highest known plant source of gamma-linolenic acid (an omega-6 fatty acid, also known as GLA, that is believed to be anti-inflammatory, unlike many other omega-6s). The leaves of borage taste a bit like a cucumber. They are wonderful in a salad, although some people are put off by their slightly prickly texture. You can also make a tasty, springy spread for veggies or bread by chopping the young leaves and combining them with a soft cheese (such as cream cheese, chevre or ricotta), green onions or chives, and diced onion or shallot. The striking blue flowers add a decorative touch in the ice cubes of a summer cocktail or when sugared and used to garnish a cake. Borage flowers can also add delicate flavor to herbal vinegars (and this is the only effective method of preserving them).

In the Medicine Cabinet: The leaves of this plant are said to lift the spirits and support the health of our endocrine systems. I like them in tea throughout the winter when I get starved for cheery sunshine. Simply pick the leaves and dry them in a dehydrator on the lowest setting or between old window screens. Store the dried leaves whole. To make tea, cover with boiling water, let steep for 10 minutes, strain and enjoy. Use caution if using borage internally long-term, or if using supplements. Regular consumption of the whole plant is safe, but in frequent, high doses (greater than 2 grams a day), some liver concerns exist.

3. Oats (Avena sativa)

In the Garden: The oat plant is beloved the world over as a food, and it’s a wonder in the garden. As a cover crop, it suppresses weeds, prevents erosion in soils that would otherwise be bare over winter, and increases the soil’s nitrogen content—its deep roots suck nitrogen into shallower earth so it’s accessible to the next planting. When the whole plant is tilled back into the soil it provides so much bulk that the tilth, or soil structure, is improved. If you plan to eat your oats, grow hulless ones, which require less processing after harvest. Harvest oats in the “dough” stage: after the “milk” stage, when kernels still contain milky fluid, but before the “dead ripe” stage, when they are hard. In the dough stage, the kernels should be soft and dentable with a fingernail.

In the Kitchen: Oats are a good source of important nutrients including calcium, magnesium, phosphorus, potassium and folate. Whole oats are known as oat groats, and they make a nutritious food for baking and cooking.

In the Medicine Cabinet: All parts of the oat plant have traditionally been used as a nervous system tonic, primarily because of its nutritional make-up. Milky oats (the immature oat seed) and oat straw make a relaxing tea that contains calcium and bone-nourishing vitamins. To make it, pick a tender green oat stalk, cut it into pieces, cover with 2 cups boiling water and steep for 15 minutes or as long as overnight. Strain and drink, reheated or cold.

4. Red Clover (Trifolium pratense)

In the Garden: Red clover excels in the apple orchard, where it attracts the predator of the wooly aphid, and it’s also popular to grow under grapevines, which require well-drained soil to grow well. This member of the bean family fixes nitrogen in nodules around its roots, improving soil fertility. Red clover is also a specialist at making soils less compacted and less acidic. In the process its presence usually means improved soil drainage and lots of beneficial insects.

In the Kitchen: As a child, did you ever sit in a meadow and sip the nectar out of the white segment of the red clover flower? You were doing your body a favor: Red clover is a source of nutrients including calcium, chromium, magnesium, potassium, thiamin and vitamin C. To enjoy this same treat as an adult, add a handful of the red flowerettes, plucked from a flower head, to your rice along with a bit of butter. Delicious!

In the Medicine Cabinet: Red clover flowers are traditionally enjoyed in the spring as they’re blooming. The flower is rich in vitamins and minerals and is a well-known blood thinner, which can help prevent blood clots from forming. It is often used in a tea as a gentle way to improve the condition of our liver and blood. Preliminary evidence also suggests that the isoflavones in red clover may help stop cancer cells from growing or kill cancer cells in test tubes, according to the University of Maryland Medical Center.

5. Elderberry (Sambucus nigra ssp. canadensis)

In the Garden: Plant this perennial shrub near your compost pile and stand back to watch the magic. The soil underneath the shrub will become much better aerated, and elderberry tends to work as a compost activator, assisting you in breaking down yard and kitchen refuse. The leaves can be made into a tea and sprayed to control aphids, carrot root fly, cucumber beetles and peach tree borers.

In the Kitchen: This plant is one of the next hot cash crops. The foodie world has caught on to how delicious the berries are in syrups, jellies and jams, wines and more. They may be a lot of work to harvest, but they are delicious!

In the Medicine Cabinet: Elder is one of our most beloved plants for cold and flu season. It is known to combat eight various strains of the influenza virus. The berry is used for this purpose and, while it can be tinctured, it’s so delicious that it’s better in teas and syrups.

6. Alfalfa (Medicago sativa)

In the Garden: While it’s commonly used as a “green manure” crop, alfalfa has more to offer in the garden. Alfalfa accumulates calcium, nitrogen, iron, magnesium, phosphorus and potassium in its amazingly extensive root system. Extending on average 20 to 30 feet deep, alfalfa breaks up hard clay, improves soil drainage and holds water content for neighboring plants. It is a beneficial insect attractor with a special interest for bees. It can even be used as a compost activator.

In the Kitchen: Alfalfa sprouts are well known, but the tender leaves tend to be underused. They are surprisingly nutritious, containing the entire spectrum of B vitamins, as well as vitamins A, D, E and K. The leaves are also a good source of iron, niacin, biotin, folic acid, calcium, magnesium, phosphorous and potassium, as well as chlorophyll. The edible leaves are best in soups, broths, casseroles and smoothies. You can also use the dried leaves in tea blends.

In the Medicine Cabinet: The leaves of alfalfa are often used in teas and tinctures as a nutritional supplement. Alfalfa is considered useful for kidney, bladder and prostate conditions, and it’s often used to treat arthritis and during pregnancy, as it can help ease morning sickness and is a good source of vitamin K. You can find alfalfa in tablet form, as well.

7. Burdock (Arctium lappa)

In the Garden: You may have cursed burdock at some point as you’ve picked its burs—said to have inspired the invention of Velcro—out of clothing in autumn, but this deep tap-rooted weed is extremely useful in the garden. It is the perfect soil conditioner for the first year of a garden plot that needs help. The deep taproot breaks up hard clay and brings up minerals that have leached out of the topsoil and dropped out of reach for most other plants.

In the Kitchen: Also called gobo root in Asian markets, this root is delicious chopped and used in recipes as you would a carrot. It’s tasty added to vegetable soups or stews. Or try a veggie saute with sliced onions, garlic, kale, burdock root and carrots (both sliced into matchsticks), topped with tamari. You can also make the root into a tea by simmering 2 tablespoons fresh root (or 2 to 3 teaspoons dried root) in a cup of water for 30 minutes.

In the Medicine Cabinet: Burdock is popular in both Western and Chinese herbal medicine for its detoxifying effects—the root is traditionally used in teas and tinctures to ease symptoms of skin ailments such as acne, eczema and psoriasis. It’s also an effective liver tonic. Although eating the food might be the most tasty and useful way to use it, you can also make burdock root into tinctures or find it in capsules. Burdock can reduce blood sugar levels; use it with caution when taking insulin.

8. Garlic (Allium sativum)

In the Garden: If you’ve got roses or fruit trees, garlic should be your go-to garden superstar. Garlic is repellant to aphids, codling moths, Japanese beetles, root maggots, snails, carrot root fly, borers and even deer. A mix of garlic oil diluted with water can be used as an effective spray to repel whiteflies, aphids and fungus gnats and to deter brown rot in stone fruits and late blight in tomatoes and potatoes.

In the Kitchen: In my kitchen, cooking just doesn’t happen without garlic. Garlic makes a savory and flavorful addition to just about any meal. You can oven-roast garlic by chopping the top off a whole head (so cloves are just visible), covering with olive oil and roasting in a 300-degree oven until soft and brown. Then squeeze the garlic out of the papery skins and save the paste in the fridge or freezer. Make sure to leave some garlic in the ground to protect next year’s plants.

In the Medicine Cabinet: Fresh garlic is known as one of the world’s superfoods for its antioxidant, antibacterial, anticarcinogenic, antifungal and antiviral properties. Garlic stimulates the immune system, and it’s used therapeutically for high blood pressure and cholesterol management. You can employ garlic to fight colds and flus, sore throats, earaches, intestinal bugs and to help ward off cancer. Eating it raw is the best way to use the herb for its immune-stimulating properties. To help cooked garlic retain its maximum immune-boosting properties, crush or chop to expose it to air for 10 minutes before cooking.

9. Comfrey (Symphytum officinale)

In the Garden: The tough roots of comfrey pull up calcium, phosphorus and potassium from deep in the ground, and they can also break up hard clay. The large leaves act as a trap crop for slugs, and they can help shade smaller plants. They have a nitrogen-carbon ratio similar to manure and are helpful in the compost pile. I like them best as mulch for my tomatoes, where their high calcium level helps prevent blossom end rot.

In the Kitchen: Little used today in the kitchen due to concerns over pyrrolizidine alkaloids—which are potentially damaging to the liver—this was once a popular potherb.

In the Medicine Cabinet: Although it’s not recommended for internal use, comfrey is an excellent topical medicinal plant. The leaf and root of the plant can be used as a tea soak for rashes or in salves to heal cuts and wounds. A comfrey poultice can help ease sprains and bruises. It’s also an effective skin-soother, useful for dry skin, puffy eyes and dark undereye circles. To make comfrey oil, combine the chopped roots and leaves with olive, sunflower or almond oil in the top of a double boiler. Boil water in bottom pot for 40 minutes. Strain, let cool, then use externally.

10. Beets (Beta vulgaris)

In the Garden: What a surprise! Beets aren’t just for eating, they can also be used for soil remediation. These bleeding wonders add minerals such as magnesium to the soil and are great added to the compost pile.

In the Kitchen: Beets offer a world of nutrition, and they’re delicious pickled, added to salads, roasted or as the star of the show in a nourishing bowl of borscht.

In the Medicine Cabinet: High in antioxidants and strongly anti-inflammatory, beets are food medicine for the heart and brain, and they’re helpful for diabetics and arthritics. Like all richly hued vegetables, beets are high in phytonutrients.

As Always, Caution

Although the herbs in this article are quite safe, we always recommend consulting a medical professional before using therapeutic levels of natural medicine. This is especially important when combining herbal medicines with pharmaceuticals, in children, and in nursing and pregnant women.

Dawn Combs is the owner of Mockingbird Meadows Herbal Health Farm and director of its Eclectic Herbal Institute. She is the author of Conceiving Healthy Babies: An Herbal Guide to Support Preconception, Pregnancy and Lactation.