Beets give nutrients back into the soil, which cabbage appreciates throughout the growing season. Also, both plants can be harvested around the same time, meaning there’s minimal root disturbance for either.
It’s never a good idea to keep crops from the same family near one another because they’re susceptible to the same pests and diseases.
Celery is one of the best companion plants for cabbage. Its aroma deters the white cabbage moth, which, shockingly, feeds on cabbages.
Tomatoes are heavy nitrogen feeders, as are cabbages. Gardening lore says that cabbages can inhibit the growth of tomatoes, but there’s no real proof of this.
Borage is another good cabbage companion plant because it attracts pollinators and predatory insects. At the same time, it repels cabbage moths.