What Companion Plants Work Well with Tomatoes in California?
Basil, marigolds, and carrots are your best bets. Each one earns its spot next to tomatoes for a different reason, and all three thrive in the same conditions that tomatoes love in Santa Cruz County.
Basil is the classic companion, and the science backs it up. UC Agriculture and Natural Resources research confirms that certain aromatic herbs can help deter common pests like aphids and whiteflies when planted nearby. Basil also attracts pollinators when it flowers, which helps with fruit set. Plant it close (within 12 inches) and let some plants bolt later in the season.
Marigolds (French marigolds, specifically) release compounds from their roots that suppress root-knot nematodes, a real problem in California garden soil. They also draw hoverflies and other beneficial insects that feed on aphids. Carrots and parsley work well as understory companions because their deep roots don't compete with tomato roots, and their flowers attract predatory wasps.
What to keep away: fennel inhibits tomato growth and should be planted elsewhere in your garden. Brassicas (broccoli, cabbage, kale) are heavy feeders that compete for the same nutrients, so give them their own bed. In small raised beds, companion planting is especially useful because you're making every square foot count.
This week: When you plan your tomato bed layout, tuck three basil plants between every two tomato plants, and border the bed with a row of French marigolds.
For a complete pairing chart, our free Companion Planting Guide covers vegetables, herbs, and flowers that help (or hurt) each other. You can also read our full guide on growing tomatoes in Santa Cruz for spacing and layout tips.
