Planting two or more crops or other plants together in the hopes that they will help each other grow and thrive is known as companion planting.

Companion planting works because plants can have all manner of effects on their surrounding environment - they may beneficially change the soil's chemistry, for example, and prevent other plants or animals from encroaching on their territory. Many provide benefits that encourage other plants to grow. for loads more tips on growing your own

Companion planting can help establish a healthy, lush garden, and the best argument for the technique is that of variety; instead of having blocks of a single plant in your garden, a variety of plants mixed together can help attract a year-round range of helpful pollinators and deter unhelpful pests.
It's important to first investigate what and how much you should plant together, and some of your plantings may end up being be trial and error. Traditionally basil is supposed to help protect tomatoes from flies - but in practice you may need to plant an enormous amount of basil to have any real effect.

Make sure that if you are planting any toxin-releasing species, you aren't doing it near something vulnerable to natural chemical warfare! Planting cabbages near tomatoes or potatoes near pumpkin may reduce growth in the latter crops, for example.
Strong-smelling herbs, such as mint, chives and dill can help to keep away insects from the garden, and caterpillars can be lured away from your lettuces by planting a 'trap crop' of nasturtiums close by.

Asparagus -----Parsley, capsicum, basil, lettuce and tomato

Basil----- Tomato, most vegetables and herbs

Beans----- Potato, corn, lettuce,  cucumber, strawberry, celery, carrots, cauliflower, radish, spinach,

Beetroot----- Onion, lettuce, spinach and silver beet

Broccoli----- Onions, leeks and celery

Brussells Sprout -----Potato

Cabbage----- Onion

Carrot----- Peas, leeks, lettuce and chives

Cauliflower----- Onions and leeks

Celery -----Tomato, leeks and beans.

Corn----- Lettuce, peppers, cucumber, beans and peas

Cucumber----- Radish, lettuce, beans, peas and artichokes

Leeks----- Cabbage, celery, onion and celeriac

Lettuce----- Beetroot, strawberry, radish and corn

Mint----- Cabbage and tomato

Onion----- Lettuce, cabbage and carrots

Parsley----- Tomato, asparagus, carrot and peppermint

Parsnip----- Shallots, chives and lettuce

Peas----- Cucumber, radish, turnips, corn, carrots and beans

Pepper Chili----- Cucumber, squash and lettuce

Potato----- Tomato, cucumber, sunflower, green beans, peas and broad beans

Pumpkin----- Corn

Radish----- Peas, lettuce and nasturtium

Shallots----- Carrots, beetroot and mint

Spinach----- Strawberry and most plant

Strawberry-----  lettuce and bush beans

Tomato----- Asparagus, peppers and basil

Zucchini Courgette----- Parsley, tomato, silver beet, spinach, squash, corn and capsicum