There is always going to be someone in the office that you don’t like. You also have someone else that you’re happy to hang out with after work. Geoff in accounts has that way of annoying you whenever he cracks his lame jokes. Dave makes you laugh and you have a lot in common. He also knows how to warn you when the boss is walking in your direction when you’re playing FreeCell instead of working on that spreadsheet.

Plants don’t know much about spreadsheets but they certainly have their own personal preferences. If you sow dill next to carrots then the smell from those frilly chaps will kill the carrots dead. Conversely, the musky scent from marigolds frightens aphids away from your tomatoes. Nasturtiums attract cabbage caterpillars who will then feast happily on any bugs that you don’t want.

Companion planting can benefit your crops in six very distinct ways:

  • attraction
  • pest control
  • nitrogen fixing
  • physical protection
  • yield boosts
  • as a sacrificial decoy

It’s also important to plant simultaneously to ensure that your main crops get protection at the seedling stage. When vegetables start to grow, they are under constant attack from the elements and predators without the necessary strength and resilience.

Attraction and Pest Control

The roots, stems, leaves and flowers of plants all produce gases, which are either deeply attractive or horribly repugnant. Dill exudes a scent that is attractive to hoverflies – and hoverflies love to eat aphids, which also love to eat your plants. Carrots and leeks are great mutual companion plants as they give off gasses that deter each other’s pests. Conversely, you need to avoid planting schemes that repel each other with their respective gasses.

Nitrogen Fixing and Physical Protection

Nitrogen is the wonder gas that you find in just about any commercial fertiliser. The vast majority of plants need a healthy supply of nitrogen to their roots to ensure steady and healthy growth. Certain plants such as the pea family and green manures such as fenugreek and mustard have nitrogen nodules attached to their roots, which break off and “fix” the soil. Plant these next to nitrogen-loving crops like tomatoes for a bountiful yield.

Some plants act as protection for others. Any plant with large overhanging leaves makes a great canopy for smaller, shade-loving vegetables. Rapid growers also shield slow growing plants in their shade and can stop vegetables like lettuces from bolting in the fierce glare of the summer sun. Other plants have prickles, which deter slugs and snails or inquisitive birds. Tall grasses act as a windbreak in exposed areas.

Yield Boosts and Act as a Sacrificial Decoy

White cabbage butterflies are beautiful creatures, but they also love eating cabbages. Slugs can strip an entire rhubarb plant of its leaves and kill it overnight. It’s a good idea to designate an area of vegetables and herbs specifically as pest food. That way, they can happily gorge themselves into a stupor while elsewhere your main crop matures to harvest.

Planting vegetables, which improve the soil either through mineral deposits or by breaking up poor drainage, ensures the following year’s crop rotation will get off to a good start. Learn the benefits of each plant and your garden will become a much happier and companionable place for all your vegetables.