Best Companions are Garlic - Turnip - Tansy and Rue
"Companion Planting is the growing together of all those elements and beings that encourage life and growth; the creation of a microcosm that includes vegetables, fruits, trees, bushes, wheat, flowers, weeds, birds, soil, microorganisms, water, nutrients, insects, toads, spiders, and chickens." - John Jeavons - How to Grow More Vegetables Than You Ever Thought Possible
Raspberries are bad companion plants for eggplant, tomatoes, potatoes, peppers and related crops. Strawberries, although not related to the nightshade family, should be kept away from raspberry family plants for the same reason. These crops are susceptible to, and transmit verticillium wilt, to which most raspberries are highly susceptible.
Raspberries also attract potato phytophthora blight so should also not follow potatoes, or related crops in the rotation.
They should not be mixed with other raspberry or blackberry varieties If you are growing two or more varieties, or growing blackberries and any variety of raspberry they should be kept as far apart as possible, at least 500 feet. This applies to boysenberries and loganberries as well.
Never start a new raspberry patch where one has been in the past 4-5 years. Fungal diseases, pathogens and nematodes that favor raspberry will still be festering in the soil.
Good Neighbors are Garlic, Turnip, Rue, Tansy, Marigold. All of which repel harmful insects such as ants, flies, moths and assorted flying insects that are harmful to fruits and berries.
Garlic discourages Aphids,Flea beetle,Japanese beetle, and spider mites as well as vampires and members of the opposite sex. Garlic accumulates sulfur, a natural fungicide which will help in the garden with disease prevention.
Tansy, a fern-like flowering plant that produces bright yellow flowers is a general insect repellent. It also increases Potassium levels in the soil and is beneficial to most other garden plants. Its leaves are toxic to people, pets and livestock.
Rue is somewhat toxic and contrary to what some herbalists suggest - it should not be applied it to your skin as it may invoke allergic reactions. It is known to repel the Japanese Beetle which feeds heavily on Raspberry in all stages of its life cycle.
Turnips help to deter Harlequin Bugs and related stinkbugs. Yarrow,also helps to deter Harlequin bugs. Wormwood serves as an insect repellent.
Planting Raspberries near pine trees is helpful. Pine Trees and Evergreens will add to the acidity of the soil. The pine needles break down and add essential nutrients as well as increasing the acidity of soil. Raspberries thrive on a pH 5.5 - 6.5.
Other berries, blueberries in particular, will also benefit from the acidic conditions created by pine needle mulch. Raspberries, require well-drained soil and partial to full sun, so don't plant them in the full shade of the pine tree, just partial shade. Also don't plant them in conjunction with the other berries.
Avoid Fennel which is allelopathic to most garden plants. It exudes compounds designed by nature to eliminate competing plants from its immediate area. Dill is one of the few garden crops that can be grown with it.