Have a look at part one to find out more about what companion planting is and why you would do it.
The first aspect of plant companionship is simply about plants being together in close spacing. The spacing is especially important when the plants are small.
The second aspect is whether, and if so to what extent, different plants prefer the company of other plants.
In terms of plants liking other plants, it’s about whether their respective growth habits complement each other. A classic combination is dwarf French marigolds growing low between tall cordon tomatoes - they look stunning together. It also turns out that marigolds release limonene which deters aphids.
One companionship myth pertains to fennel, which is said not to grow well with other plants. This is simply not true. In fact, I find the opposite after I pop in Florence fennel between other plants like lettuce and spinach. When the older plants come to their final harvests, the fennel establishes a root system. Then after a month or so, I twist out the lettuce or spinach, and the fennel swells nicely.
Fennel as a companion to spinach and lettuce
Flavour as your guide
I love how plants that grow well as companions often taste good together as well. For example, basil grows happily close to tomato plants. This won't make a huge harvest because the tomatoes take a lot of light and moisture, but the basil keeps cropping slowly and healthily.
Sweet basil companion to a tomato plant and a marigold nearby too
Other classics along this vein include spring onions and celeriac, carrots and onions, lettuce and coriander, and garlic with almost anything including beetroot.
Have fun trying a few combinations. And remember to keep your small seedlings together.