Here's some suggestions for Companion Planting; plants that will enhance each other and plants that can't stand each other.

Plant Name Friend Foe Notes ASPARAGUS Basil, Parsley, Tomato None Parsley and asparagus are mutually beneficial in promoting one another's health and vigor; Tomatoes contain a substance called solanine, which protects against asparagus beetles, but tomatoes also attract the natural predators of the asparagus beetle.
Asparagus Rust, Fusarium, Needle Blight, Purple Spot.
Pests: Asparagus Aphid, Asparagus Beetles.
BASIL Bell Pepper, Carrots, Marigold, Parsley, Tomato Rue Rue and basil are natural enemies BEANS, BUSH
(Butter, Green, Snap, String, & Wax)
Beets, Cabbage Family, Carrot, Celery(plant sparingly), Corn, Cucumber, Eggplant, Lettuce, Pea, Marigold, Potato, Radish, Rosemary, Savory, Strawberry, Tansy, Tomato Fennel, Gladiolus, Onions and Other Alliums Only scented Marigolds will work, but not the Mexican variety: they act as a herbicide on beans and cabbage; Carrots help beans, but beans don't help carrots; Strawberries and bush beans grow much better together than separately. BEANS, POLE Carrots, Corn, Cucumber, Eggplant, Lettuce, Pea, Radish, Savory, Tansy Beets, Cabbage, Gladiolus, Kohlrabi, Fennel, Onion and other Alliums, Sunflower Carrots help beans, but beans don't help carr BEETS Bush Beans, Cabbage, Carrots, Kohlrabi, Lettuce, Onions, Sage Mustard, Pole beans These plants grow at different levels in the soil, so they do not compete for nutrients and maximize planting space; Mustard inhibits growth. BLACKBERRIES and other cane fruit Tansy Raspberries Raspberries and Blackberries should be kept apart because of virus disease; Tansy repels harmful insects. CABBAGE FAMILY (Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Collards, Kale, Kohlrabi, Rutabaga, Turnip) Beets, Bush Beans, Celery, Chamomile, Cucumber, Dill, Garlic, Geranium, Hyssop, Marigolds, Mint, Nasturtiums, Onions, Potatoes, Rosemary, Rue, Sage, Tansy, Thyme. Grapes, Mexican marigolds, Pole Beans, Rue, Strawberries, Tomato. Mint is very invasive, but it enhances growth and health and discourages aphids, ants, flea beetles, white cabbage moths and even bunnies and other rodents; Marigolds must be scented to ward off insects, but not the Mexican variety, which acts as a herbicide on cabbage and beans; Rosemary and Sage deter cabbage moths; Thyme deters the cabbageworm; Garlic wards off pests; Chamomile improves the flavor of cabbage and enriches the soil with calcium, potassium and sulfur; Cabbage and grapes are ‘natural enemies' - chemical warfare may be involved. CARROTS Chives, Flax, Leeks, Leaf Lettuce, Onions, Parsley, Peas, Radish, Rosemary, Sage, Tomato Dill, Anise Dill and anise will reduce carrot crop; Parsley and sage protect against carrot flies by masking the carrot odor that attracts the flies; Leeks improve growth and repel carrot flies. CELERY Bush Beans, Bush Beans, Cabbage Family, Leeks, Tomatoes None Leeks improve its growth and repel carrot flies CORN Amaranth, Beans, Cucumber, Geranium, Marigolds (any), Melon, Peas, Pumpkin, Potatoes, Squash, Sunflower Tomatoes Sunflower increases corn yield and relieves fall army worm/corn protects sunflower from insects; Ground vine plants shade the soil, aiding in moisture retention and their prickly vines may discourage raccoons and other corn predators; Climbing vine plants help anchor the corn stalk and make it less vulnerable to wind damage; Geranium repels Japanese beetles and cabbage worms; Peas and beans replenish nitrogen in the soil; Tomatoes and corn are subject to the same pest, the tomato fruit worm/corn earworm. CUCUMBER Beans, Chamomile, Corn, Peas, Carrot, Nasturtium, Radish, Sunflower, Cabbage Aromatic Herbs - esp. sage, Potatoes Nasturtium deters cucumber beetles, aphids, squash bugs and other pests. Flowers are edible; Chamomile improves the flavor of cucumbers and enriches the soil with calcium, potassium and sulfur. EGGPLANT Bush Beans, Pole Beans, Spinach None Growing among bush beans protects from attacks of the Colorado potato beetle. DILL Cabbage, Cucumbers, Lettuce, Onions Carrot, Tomato Protects tomatoes against red spider infestation; Garlic inhibits the growth of peas and beans. GARLIC Roses, Tomatoes Aromatic Herbs, Beans, Peas, Aromatic Herbs, Beans, Peas, Potatoes Protects tomatoes against red spider infestation; Garlic inhibits the growth of peas and beans. FENNEL None Disliked by most vegetables and herbs, inhibited by coriander and wormwood Plant by itself, away from any other plants GRAPES Elm trees, Geranium, Hyssop, Mulberry trees, Roses Cabbage Cabbage and grapes are ‘natural enemies'- chemical warfare may be involved; Grapes growing on elm or mulberry trees have been found to be mildew and brown-rot free; Hyssop increases yield. LETTUCE Beans(all varieties), Beets, Carrots, Cucumbers, Onions, Radishes, Strawberries None Lettuce grows well with its companions; Onions may repel rabbits and other pests. LEEK Beets, Carrots, Celeriac, Celery, Onions Beans, Peas Carrots benefit leeks and they in turn repel the carrot fly. MELONS Corn, Morning Corn, Morning Glory, Nasturtium, Radish, Sunflower Potato Morning Glory thought to assist in melon seed germination.
ONION Beets, Cabbage, Carrots, Celery, Chamomile, Cucumbers, Leeks, Lettuce, Pepper, Rosemary, Squash, Strawberries, Tomato Beans, Peas, Sage Leeks improve onion growth and repel carrot flies; Chamomile improves the flavor of onions and enriches the soil with calcium, potassium and sulfur; Beets improve production of onions. PEAS Carrots, Cucumbers, Corn, Turnips, Radishes, Beans, Potatoes, Aromatic Herbs Garlic, Onions, Leeks, Shallots Carrots produce a compound that greatly enhances pod production and quality PEPPER Asparagus, Basil, Beets, Eggplant, Lettuce, Parsley, Rhubarb, Spinach, Tomato Fennel Growing requirements similar to basil; Peppers are brittle plants, so they benefit from being next to the taller plants for wind-protection. POTATO Bush Beans, Cabbage Family, Corn, Eggplant, Flax, Pea Cucumber, Melons, Pumpkin, Raspberry, Squash, Sunflower, Tomato Bush beans protect against the Colorado potato beetle; the potato protects the bean against the Mexican bean beetle; Flax contains tannin that repels the Colorado Potato Bug; Tomatoes make potatoes more susceptible to potato blight; Raspberries make potatoes susceptible to blight; Flax enhances growth and repels the Colorado potato beetle. PUMPKIN Corn, Radish Potato Potato and Pumpkins inhibit one another's growth. RADISH Beans, Beets, Carrots, Corn, Cucumbers, Lettuce, Nasturtium, Squash, Spinach, Parsnips Cabbage, Cauliflower, Brussels Sprouts, Broccoli, Hyssop, Kohlrabi, Turnips Nearby lettuce may make radishes more tender; Beans increase nitrogen in the soil. RASPBERRY(Red) Garlic, Tansy Blackberries, Black Raspberry, Potato Garlic and tansy repel insects; Blackberries and black and purple raspberries should be planted at least 600 feet away from the red varieties because of virus disease susceptibility. ROSE Chives, Garlic, Geranium, Hyssop, Lupine, Onion, Shallots, Tansy, Tomato Boxwood and other woody plants with prolific root systems Garlic causes roses to produce a stronger perfume; Parsley protects against rose beetles; Onions repel rose chaffers; Lupines increase soil nitrogen and invite earthworms; Tomatoes protect from black spot disease; Hyssop deters flea beetles and cabbage moths; Woody plants with large root systems will compete for soil nutrients.
Taste of cabbage and beans is improved by Rosemary; Grows well with sage.
ROSEMARY Beans, Cabbage, Carrot, Sage None Taste of cabbage and beans is improved by Rosemary; Grows well with sage. SAGE Cabbage, Carrot, Rosemary Rue Sage improves the taste of cabbages. SHALLOTS Beets, Cabbage, Carrot, Chamomile, Mint, Sage, Thyme Beans, Peas The herbs improve the flavor of shallots; Beets and carrots grow at different levels in the soil, so they do not compete for nutrients. SPINACH Cauliflower, Celery, Eggplant None Spinach is rich in saponin, a soil-beneficial compound. SQUASH Corn Potato Potato STRAWBERRY Borage, Bush Beans, Lettuce, Onion, Spinach Cabbage and family members Borage increases beneficial natural minerals in the soil. It also controls insects. SUNFLOWER Corn, Cucumber Pole Bean, Potato Corn and cucumber yield is increased by nearby sunflowers; Sunflowers are also useful in aphid control. TOMATO Asparagus, Basil, Borage, Carrots, Celery, Chives, Bell Pepper, Horehound, Mint, Monarda (Bee Balm), Nasturtium, Onion, Parsley Corn, Dill, Kohlrabi, Potato, Fennel Basil improves flavor and protects against insects; Horehound encourages fruiting; Bee Balm aids in both growth and flavor (caution: Bee Balm is a mint and is invasive!); Potatoes inhibit the growth of tomatoes. THYME Cabbage family, Eggplant, Onion, Potato, Sage, Tomato None May be planted with all plants. It enhances the fragrance of other herbs, protects against insects, improved taste of companion vegetables, and is an all-around nice and useful plant.