Companion planting means placing plants together that grow well together (and may even help each other out), while avoiding placing plants together where one inhibits the other.
The companion planting charts you can find online and books shouldn’t be treated as hard science, but can be very worthwhile as a starting point when you’re trying to figure out how to lay out your beds.
Related terms are ‘intercropping’ and ‘polycultures’.
This means planting a diversity of plants together to take up different heights above and below ground, provide you with more diverse sources of food, attract diverse beneficial insects, and so on.
While I always advocate planting many different plants in order to have more diversity, extend your harvest, and invite more beneficials, I do have a counter argument – it could be better to grow just a few plants really well than 50 plants only moderately well.
In Peru, they grow around 3000 varieties of potatoes. Potatoes still make up a huge part of the diet of certain tribes there, who may not eat any greens at all.
The bottom line is that if you can learn to grow something really well so that it’s highly nutritious, I’d rather see you eat a lot of that rather than 50 different mediocre things.
On the other hand, there are benefits to a varied diet as well, and there are many benefits to having variety in the garden, and of course, I’m not a nutritionist.
Crop rotation is related. That’s where you don’t plant the same plant family in the same place for usually at least 3 years.
If squash was in that spot last year, you don’t plant squash or cucumber or melon there this year or next year, primarily because you’d be making it easier for pests to find it, and also because rotating plants can improve soil fertility.
Although crop rotation probably is a best practice, if your soil is healthy, it isn’t necessary. Farmers have grown the same crops for hundreds of years on the same land, as long as they were taking care of that land.
But I still do it, and I still do companion planting to help give me some direction when planning my beds each year.
From The Smiling Gardener