Tomatoes and Calendula
Beneficial Pair — Good Match
The gap between plausible and proven stays open here - calendula's general attractiveness to both aphids and beneficial predatory insects is documented, but a trap-cropping effect isolated for tomato pests specifically hasn't turned up in anything we located.
Mechanism: Trap Cropping
Calendula draws aphids to its own foliage, potentially pulling them away from tomatoes, while its open, accessible flowers also attract hoverflies and other predatory insects that feed on aphids throughout the garden. This dual role, trap crop and insectary plant, is documented in general polyculture literature, though with less specificity to tomatoes than nasturtium's better-studied aphid relationship elsewhere on this site.
Calendula plays two roles at once in this pairing, a modest aphid trap and a draw for the predatory insects that eat aphids, though neither role is quite as rigorously documented as nasturtium's.
Two Mechanisms, Neither as Well-Tested as Nasturtium's
Calendula shares some of nasturtium's aphid-attracting quality, and its open flower structure also draws hoverflies and other beneficial predators, giving this pairing a plausible dual benefit. The specific evidence isolating tomatoes and calendula together, rather than general polyculture observations, is thinner than what supports the tomato-nasturtium pairing.
Calendula does have one advantage worth noting on its own terms: it's an edible flower with a long tradition of use in skin salves and garden borders, so even setting the pest question aside, it's a genuinely useful plant to have around.
Spacing
Plant calendula 10-12 inches from tomato plants, similar to other trap-crop flowers on this site, positioned where it can intercept pests approaching the bed.
Watch For
Deadhead calendula regularly to keep it flowering through the season - a calendula plant that's stopped blooming loses much of its beneficial-insect-attracting value along with its aphid-drawing appeal.
Frequently Asked Questions
Can I plant calendula and nasturtium together at the same tomato bed for a stronger combined effect?
There's no reason they'd conflict - both are used the same way here, as border plantings that draw aphids and beneficial insects, so growing them together doesn't create any known problem. Whether combining two unconfirmed trap-crop mechanisms actually adds up to more protection than either alone isn't something we've seen tested, though, so treat it as reasonable garden variety rather than a proven multiplier.
Is calendula's aphid-drawing role wasted if I'm mainly growing it for the edible flowers?
No - the two uses don't conflict much. You'd typically pick flowers once they're fully open, which is also roughly when they're most attractive to visiting insects, so harvesting some blooms for salads or salves while leaving others on the plant to keep flowering works for both purposes at once.