This information again came via email, and is pretty useful, hence posting
ALFALFA: Perennial that roots deeply. Fixes the soil with nitrogen, accumulates iron, magnesium, phosphorous and potassium. Withstands droughts with it’s long taproot and can improve just about any soil! Alfalfa has the ability to break up hard clay soil and can even send its’ roots through rocks! Now that is a tenacious plant! Alfalfa is practically pest and disease free. It needs only natural rainfall to survive.
AMARANTH: A tropical annual that needs hot conditions to flourish. Good with sweet corn, it’s leaves provide shade giving the corm a rich, moist root run. Host to predatory ground beetles. Eat the young leaves in salads.
ANISE: Licorice flavored herb, good host for predatory wasps which prey on aphids and it is also said to repel aphids. Deters pests from brassicas by camouflaging their odor. Improves the vigor of any plants growing near it. Used in ointments to protect against bug stings and bites. Good to plant with coriander.
ARTEMISIAS: See Wormwood
BASIL: Plant with tomatoes to improve growth and flavor. Basil can be helpful in repelling thrips. Said to repel flies and mosquitoes. Do not plant near rue.
BAY LEAF: A fresh leaf bay leaf in each storage container of beans or grains will deter weevils and moths. Sprinkle dried leaves with other deterrent herbs in garden as natural insecticide dust. A good combo: Bay leaves, cayenne pepper, tansy and peppermint.
BEANS: All bean enrich the soil with nitrogen fixed form the air. In general they are good company for carrots, brassicas, beets, and cucumbers. Great for heavy nitrogen users like corn and grain plants. French Haricot beans, sweet corn and melons are a good combo. Keep beans away from the alliums.
BEE BALM (Oswego, Monarda): Plant with tomatoes to improve growth and flavor. Great for attracting beneficials and bees of course. Pretty perennial that tends to get powdery mildew.
BEET: Good for adding minerals to the soil. The leaves are composed of 25% magnesium. Companions are lettuce, onions and brassicas.
BORAGE: Companion plant for tomatoes, squash and strawberries. Deters tomato hornworms and cabbage worms. One of the best bee and wasp attracting plants. Adds trace minerals to the soil and a good addition the compost pile. Borage may benefit any plant it is growing next to via increasing resistance to pests and disease. After you have planned this annual once it will self seed.
BRASSICA: Benefit from chamomile, peppermint, dill, sage, and rosemary. They need rich soil with plenty of lime to flourish.
BUCKWHEAT: Accumulates calcium and can be grown as an excellent cover crop. Attracts hoverflies in droves. (Member of the brassica family.)
CARAWAY: Good for loosening compacted soil with it’s deep roots. Tricky to establish. The flowers attract a number of beneficial insects.
CATNIP: Deters flea beetles, aphids, Japanese beetles, squash bugs, ants and weevils. We have found it repels mice quite well: mice were wreaking havoc in our outbuildings, we spread sprigs of mint throughout and the mice split! Use sprigs of mint anywhere in the house you want deter mice and ants. Smells good and very safe.
CHAMOMILE, GERMAN: Annual. Improves flavor of cabbages, cucumbers and onions. Host to hoverflies and wasps. Accumulates calcium, potassium and sulfur, later returning them to the soil. Increases oil production from herbs. Leave some flowers unpicked and German chamomile will reseed itself. Roman chamomile is a low growing perennial that will tolerate almost any soil conditions. Both like full sun. Growing chamomile of any type is considered a tonic for anything you grow in the garden.
CHERVIL: Companion to radishes for improved growth and flavor. Keeps aphids off lettuce. Likes shade.
CHIVES: Improves growth and flavor of carrots and tomatoes . Chives may drive away Japanese beetles and carrot rust fly. Planted among apple trees it may help prevent scab. A tea of chives may be used on cucumbers to prevent downy mildew. See chive tea on disease page.
CHRYSANTHEMUMS: C. coccineum kills root nematodes. (the bad ones) It’s flowers along with those of C. cineraruaefolium have been used as botanical pesticides for centuries. (i.e. pyrethrum) White flowering chrysanthemums repel Japanese beetles.
CLOVER: Long used as a green manure and plant companion. Attracts many beneficials. Useful planted around apple trees to attract predators of the woolly aphid.
COMFREY: Accumulates calcium, phosphorous and potassium. Likes wet spots to grow in. Traditional medicinal plant. Good trap crop for slugs. More on comfrey.
CORIANDER: Repels aphids, spider mites and potato beetle. A tea from this can be used as a spray for spider mites. A partner for anise.
COSTMARY: This 2-3 foot tall perennial of the chrysanthemum family helps to repel moths.
DAHLIAS: These beautiful, tuberous annuals that can have up to dinner plate size flowers repels nematodes!
DILL: Improves growth and health of cabbage. Do not plant near carrots. Best friend for lettuce. Attracts hoverflies and predatory wasps. Repels aphids and spider mites to some degree. Also may repel the dreaded squash bug! (scatter some good size dill leaves on plants that are suspect to squash bugs, like squash plants, yeah that’s the ticket.) Dill goes well with onions and cucumbers. Dill does attract the tomato horn worm so it would be useful to plant it somewhere away from your tomato plants to keep the destructive horn worm away from them. We like to plant it for the swallowtail butterfly caterpillars to feed on. Even their caterpillars are beautiful.
ELDERBERRY: A spray (see insect treatments) made from the leaves can be used against aphids, carrot root fly, cuke beetles and peach tree borers. Put branches and leaves in mole runs to banish them. Yes, it works!
FLAX: Plant with carrots, and potatoes. Flax contains tannin and linseed oils which may offend the Colorado potato bug. Flax is an annual from 1-4 feet tall with blue or white flowers that readily self sows. We have quite a few flax plants return year after year here in zone 5.
FOUR-O’CLOCKS: Draw Japanese beetles like a magnet which then dine on the foliage. The foliage is pure poison to them and they won’t live to have dessert! It is important to mention that four-o”clocks are also poisonous to humans. Please be careful where you plant them if you have children. They are a beautiful annual plant growing from 2-3 feet high with a bushy growth form.
GARLIC: Plant near roses to repel aphids. Accumulates sulfur: a naturally occurring fungicide which will help in the garden. Has some value in offending codling moths, Japanese beetles, root maggots, snails, and carrot root fly. Researchers have observed that time-released garlic capsules planted at the bases of fruit trees actually kept deer away! Hey, worth a try! (see treatments: Garlic-oil spray)
GOPHER PURGE: Deters gophers, and moles.
HORSERADISH: Plant in containers in the potato patch to keep away Colorado potato bugs. There are some very effective insect sprays that can be made with the root. Use the bottomless pot method to keep horseradish contained. Also repels Blister beetles. We have observed that the root can yield antifungal properties when a tea is made from it. (See: Horseradish: Disease)
HOREHOUND: Stimulates and aids fruiting in tomatoes.
HYSSOP: Companion plant to cabbage and grapes, deters cabbage moths and flea beetles. Do not plant near radishes. Hyssop may be the number one preference among bees and some beekeepers rub the hive with it to encourage the bees to keep to their home. It is not as invasive as other members of the mint family making it safer for interplanting.
KELP: When used in a powder mixture or tea as a spray, this versatile sea herb will not only repel insects but feed the vegetables. In particular we have observed that kelp foliar sprays keep aphids and Japanese beetles away when used as a spray every 8 days before and during infestation times. If you have access to seaweed, use it as a mulch to keep slugs away.
LARKSPUR: An annual member of the Delphinium family, larkspur will attract Japanese beetles. They dine and die! Larkspur is poisonous to humans too!
LAVENDER: Repels fleas and moths. Prolific flowering lavender nourishes many nectar feeding and beneficial insects. Use dried sprigs of lavender to repel moths. Start plants in winter from cuttings, setting out in spring.
LEMON BALM: Sprinkle throughout the garden in an herbal powder mixture to deter many bugs. Lemon balm has citronella compounds that make this work: crush and rub the leaves on your skin to keep mosquitoes away! Use to ward off squash bugs!
LOVAGE: Improves flavor and health of most plants. Good habitat for ground beetles. A large plant, use one planted as a backdrop. Similar to celery in flavor.
MARIGOLDS: (Calendula): Given a lot of credit as a pest deterrent. Keeps soil free of bad nematodes; supposed to discourage many insects. Plant freely throughout the garden. The marigolds you choose must be a scented variety for them to work. One down side is that marigolds do attract spider mites and slugs.
French Marigold (T. Patula) has roots that exude a substance which spreads in their immediate vicinity killing nematodes. For nematode control you want to plant dense areas of them. There have been some studies done that proved this nematode killing effect lasted for several years after the plants were These marigolds also help to deter whiteflies when planted around tomatoes and can be used in greenhouses for the same purpose.
Mexican marigold (T. minuta) is the most powerful of the insect repelling marigolds and may also overwhelm weed roots such as bind weed! It is said to repel the Mexican bean beetle and wild bunnies! Be careful it can have an herbicidal effect on some plants like beans and cabbage.
MARJORAM: As a companion plant it improves the flavor of vegetables and herbs. Sweet marjoram is the most commonly grown type.
MINT: Deters white cabbage moths, ants, rodents, flea beetles, fleas, aphids and improves the health of cabbage and tomatoes. Use cuttings as a mulch around members of the brassica family. It attracts hoverflies and predatory wasps. Earthworms are quite attracted to mint plantings. Be careful where you plant it as mint is an incredibly invasive perennial. We have found that placing mint (fresh or dried) where mice are a problem is very effective in driving them off!
MOLE PLANTS: (castor bean plant) Deter moles and mice if planted here and there throughout the garden. Drop a seed of this in mole runs to drive them away. This is a poisonous plant. See Moles: Critter Trouble
MORNING GLORIES: They attract hoverflies. Plus if you want a fast growing annual vine to cover something up morning glory is an excellent choice.
OPAL BASIL: An annual herb that is pretty, tasty and said to repel hornworms!
NASTURTIUMS: Plant as a barrier around tomatoes, radishes, cabbage, cucumbers, and under fruit trees. Deters wooly aphids, whiteflies, squash bug, cucumber beetles and other pests of the curcurbit family. Great trap crop for aphids (in particular the black aphids) which it does attract, especially the yellow flowering varieties. Likes poor soil with low moisture and no fertilizer. It has been the practice of some fruit growers that planting nasturtiums every year in the root zone of fruit trees allow the trees to take up the pungent odor of the plants and repel bugs. It has no taste effect on the fruit. A nice variety to grow is Alaska which has attractive green and white variegated leaves. The leaves, flowers and seeds are all edible and wonderful in salads! Try our recipe for: Nasturtium Salad
NETTLES, STINGING: The flowers attract bees. Sprays made from these are rich in silica and calcium. Invigorating for plants and improves their disease resistance. Leaving the mixture to rot, it then makes an excellent liquid feed. Comfrey improves the liquid feed even more. Hairs on the nettles’ leaves contain formic acid which “stings” you.
PARSLEY: Plant among and sprinkle on tomatoes, and asparagus. Use as a tea to ward off asparagus beetles. Attracts hoverflies. Let some go to seed to attract the tiny parasitic wasps. Parsley increases the fragrance of roses when planted around their base. Rose problems? See: Rose
PEPPERMINT: Repels white cabbage moths, aphids and flea beetles. It is the menthol content in mints that acts as an insect repellant. Bees and other good guys love it.
PEPPERS, HOT: Chili peppers have root exudates that prevent root rot and other Fusarium diseases. Plant anywhere you have these problems. Teas made from hot peppers can be useful as insect sprays.
PENNYROYAL: Repels fleas. Many people are now using pennyroyal as an alternative lawn. The leaves when crushed and rubbed onto your skin will repel chiggers, flies, gnats, mosquitoes and ticks. Smells nice too!
PETUNIAS: They repel the asparagus beetle, leafhoppers, certain aphids, tomato worms, Mexican bean beetles and general garden pests. A good companion to tomatoes, but plant everywhere. The leaves can be used in a tea to make a potent bug spray.
PURSLANE: This edible weed makes good ground cover in the corn patch. Use the stems, leaves and seeds in stir-frys. Pickle the green seed pod for caper substitutes.
RADISH: Plant radishes with your squash plants. Radishes may protect them from squash borers! Anything that will help prevent this is worth a try. Planting them around corn and letting them go to seed will help fight corn borers.
ROSEMARY: Companion plant to cabbage, beans, carrots and sage. Deters cabbage moths, bean beetles, and carrot flies. Use cuttings to place by the crowns of carrots for carrot flies. Zones 6 and colder can overwinter rosemary as houseplants or take cuttings.
RUE: Deters Japanese beetles in roses and raspberries. To make it even more effective with Japanese beetles: crush a few leaves to release the smell. Repels flies and has helped repel cats for us. Some say you should not plant it near cabbage, basil or sage. A pretty perennial with bluish-gray leaves. May be grown indoors in a sunny window. Rue can cause skin irritation! Remedy: See cats and dogs: Rue spray.
SAGE: Use as a companion plant with broccoli, cauliflower, rosemary, cabbage, and carrots to deter cabbage moths, beetles, black flea beetles and carrot flies. Do not plant near cucumbers or rue. Sage repels cabbage moths and black flea beetles. Allowing sage to flower will also attract many beneficial insects and the flowers are pretty. There are some very striking varieties of sage with variegated foliage that can be used for their ornamental as well as practical qualities. More on sage.
SOUTHERNWOOD: Plant with cabbage, and here and there in the garden. Wonderful lemony scent when crushed or brushed in passing. Roots easily from cuttings. Does not like fertilizer! It is a perennial that can get quite bushy. We have started to cut it back every spring and it comes back in not time. A delightful plant that is virtually pest free.
SUMMER SAVORY: Plant with beans and onions to improve growth and flavor. Discourages cabbage moths. Honey bees love it.
SUNFLOWERS: Planting sunflowers with corn is said by some to increase the yield. Aphids a problem? Definitely plant a few sunflowers here and there in the garden. Step back and watch the ants herd the aphids onto them! We have been doing this for years and it is remarkable. The sunflowers are so tough that the aphids cause very little damage and we have nice seed heads for our birds to enjoy! Talk about a symbiotic relationship!
TANSY: Plant with fruit trees, roses and raspberries keeping in mind that it can be invasive and is not the most attractive of plants. Tansy which is often recommended as an ant repellant may only work on sugar type ants. These are the ones that you see on peonies and marching into the kitchen. At least for us placing tansy clippings by the greenhouse door has kept them out. Deters flying insects, Japanese beetles, striped cucumber beetles, squash bugs, ants and mice! Tie up and hang a bunch of tansy leaves indoors as a fly repellent. Use clippings as a mulch as needed. Don’t be afraid to cut the plant up as tansy will bounce back from any abuse heaped on it! It is also a helpful addition to the compost pile with its’ high potassium content.
TARRAGON: Plant throughout the garden, not many pests like this one. Recommended to enhance growth and flavor of vegetables.
THYME: Deters cabbage worms. Wooly thyme makes a wonderful groundcover. You may want to use the upright form of thyme in the garden rather than the groundcover types. Thyme is easy to grow from seeds or cuttings. Older woody plants should be divided in spring.
WHITE GERANIUMS: These members of the pelargonum family draw Japanese beetles to feast on the foliage which in turn kills them.
WORMWOOD: Keeps animals out of the garden when planted as a border. An excellent deterrent to most insects. A tea made from wormwood will repel cabbage moths, slugs, snails, black flea beetles and fleas effectively. The two best varieties for making insect spray are Silver King and Powis Castle. Adversely Powis castle attracts ladybugs which in turn breed directly on the plant. Silver Mound is great as a border plant and the most toxic wormwood. Note: As wormwood actually produces a botanical poison do not use it directly on food crops. We personally have seen no evidence of artemisias suppressing the growth of plants other than seedlings though many say it does.
YARROW: Yarrow has insect repelling qualities and is an excellent natural fertilizer. A handful of yarrow leaves added to the compost pile really speeds things up. Try it! It also attracts predatory wasps and ladybugs to name just two. It may increase the essential oil content of herbs when planted among them.