How Do I Plan a Companion Planting Layout from Scratch?

Companion planting works best when planned before you start sowing rather than retrofitted into an existing layout. A little planning time in winter or early spring — before seeds are ordered and beds prepared — means you can design combinations that work together logistically, avoid bad pairings, make efficient use of space and timing, and ensure that companion plants are available when they are needed. The planning process does not need to be complex; a simple, systematic approach is all that is required.

Step 1: List your main crops and their needs

Write down every crop you plan to grow this season and note its primary vulnerability — what typically goes wrong with it in your garden. Tomatoes: whitefly, poor fruit set. Brassicas: cabbage white caterpillars, aphids. Carrots: carrot fly. Beans: blackfly. Each vulnerability suggests a specific companion: marigolds near tomatoes, nasturtiums as a trap crop for beans, aromatic herbs near carrots. Once you know what problem you are solving, choosing the companion is straightforward.

Step 2: Note timing and space requirements

Companions need to be present at the right time to be effective. Marigolds need to be established before tomatoes are transplanted — so plan to sow them four to six weeks earlier. Nasturtiums should be sown at the same time as beans so they are growing alongside from the start. Check the space requirements of each companion — a borage plant at full size needs a significant footprint, while chives take almost none. Ensure the companion will not shade, crowd, or otherwise disadvantage the main crop.

Step 3: Consider crop rotation

If you rotate crops between beds each season — which is good practice for managing soil-borne pests and diseases — plan your companion pairings to rotate together. The brassica bed with its nasturtium and thyme companions moves to a new location each year. The legume bed and its nitrogen-fixing companions rotate behind the brassicas. Think of each companion group as a unit that moves through the rotation together, building a cumulative benefit over multiple seasons.

Keeping it simple

Start with two or three key companion combinations rather than trying to redesign the entire garden at once. Marigolds near tomatoes, nasturtiums near beans, and clover in the paths between beds will deliver measurable benefits with minimal complexity. Observe what works in your specific garden over one season, then expand and adapt the following year based on what you noticed.