Calendula for the Veg Patch: Edible Petals, Real Pollinator Value, and a Companion-Planting Myth

Calendula feeds the insects that eat garden pests, and its petals are edible. It is not shown to repel pests. A 2017 study found that Calendula officinalis, grown as a floral resource, increased the population of a predatory flower bug, Orius sauteri, and that this helped suppress aphids and thrips in laboratory and greenhouse work. That is the evidenced reason to grow it among vegetables: it feeds predators, it does not shield your crops.

Gardeners plant calendula and nasturtiums near runner beans and tomatoes in the hope of effects like the French marigold's (RHS). No trial shows it.

Calendula is not Tagetes

"Marigold" is a common name shared by two unrelated genera. Calendula officinalis (pot marigold) is a hardy annual in the daisy family with orange or yellow daisy-like flowers, grown for its flowers and for insects. Tagetes patula and T. erecta (French and African marigold) are a separate genus. A glasshouse trial found French marigolds grown among short-vine tomatoes slow whitefly, through limonene, but mixing tomatoes with other plants, without Tagetes, had a similar effect (RHS). None of that evidence involves calendula. See the companion planting article.

Garden Organic advises growing brightly coloured marigolds in the greenhouse with tomatoes to attract whitefly away from the tomato plants. That is advice, not a tested result, and it does not specify the genus.

Pollinator and predator value

RHS tags Calendula officinalis as a Plants for Pollinators plant and a cut flower. Garden Organic says pot marigolds are loved by lacewings and ladybirds, and suggests mixing calendula among vegetables, alongside coriander or fennel flowers, Californian poppy and poached-egg plant, for predatory insects.

The most precise evidence is Zhao et al. (2017, Pest Management Science), which tested Calendula officinalis as a floral resource for Orius sauteri against the aphid Myzus persicae and the thrips Frankliniella occidentalis, in the laboratory and in a greenhouse. The calendula increased predator population growth, and suppression of aphids and thrips was enhanced. The effect runs through the predator, not calendula acting on pests. It was a study of one predator, in the laboratory and a greenhouse, not a field trial in a mixed vegetable bed.

Calendula can also host the pests: it may be susceptible to aphids, powdery mildews and a virus (RHS), so do not count on it protecting its neighbours.

Claims checked

Three claims circulate about calendula as a companion: that it deters aphids or whitefly by scent, that it traps pests, and that it masks the smell of neighbouring crops. Neither RHS nor Garden Organic attributes a scent-deterrent compound to calendula. The wider idea that scent confuses pests is also doubtful: research at Warwick Crop Centre found insects land on green surfaces and avoid brown soil, and that colour, size and shape matter more than odour.

Growing calendula in Scotland

Hardiness is its practical advantage: H5The RHS's H1a–H7 scale for how much cold a plant can survive outdoors, H1a being tender indoor-only and H7 hardy anywhere in the UK. Full definition →, hardy in most places throughout the UK even in severe winters, in sun or partial shade, on exposed or sheltered sites. It likes a light, poor, free-drainingSoil that lets water pass through quickly rather than pooling, so roots aren't sitting in wet ground after rain. Full definition → soil. No source gives a Scottish sowing date. Sow outdoors from March to May (Garden Organic), once the local frost risk has passed, and expect a harvest from June to September. Waiting for frost to pass pushes the first flowers back too, so a late sowing means a later harvest. Plants reach 30 to 60cm tall and wide, and seedlings need thinning or transplanting to 20cm apart (Garden Organic). Seedlings are soft growth, so protect them from slugs as you would any transplant.

DeadheadRemoving spent flowers before they set seed, which redirects a plant's energy into further flowering rather than seed production. Full definition → regularly to prolong flowering and pinch outRemoving the soft growing tip of a stem to stop upward growth and make the plant branch out sideways instead. Full definition → terminal shoots to encourage bushy growth. Keep picking to encourage more flowers. Cut off the seed heads to prevent excessive self-seeding, which otherwise happens freely; if you leave them on, calendula returns and spreads in later years. Garden Organic groups calendula with lettuce and chicory in the daisy family, Asteraceae, for crop rotationMoving each crop family to different ground each year, on a multi-year cycle, so pests and diseases that build up in soil don't get a repeat host. Full definition → planning, so avoid following them with each other in the same bed year after year, because the same plant family in the same ground lets pests and diseases build up.

Eating calendula

Calendula petals have an intense colour and a peppery taste useful in soups, stews and puddings. Pot marigold flavours range from spicy and bitter to tangy and peppery, and the petals can be sprinkled on soups, pasta, salads and rice. Powdered petals, sometimes called poor man's saffron, add a golden hint to herb butter, spreads, soups and scrambled egg: the name refers to the colour, and the flavour is nothing like saffron. Petals can also be dried, pickled in vinegar or added to oil or butter, and young leaves are edible too (Garden Organic).

As with any edible flower, avoid plants beside roads or soiled by dogs and other pets. Unless shop-bought plants are labelled for culinary purposes, grow them on for at least three months to reduce the risk of pesticide residues, and only harvest subsequent flowerings. Accurate identification is essential, so if you are in doubt, do not eat it, and people prone to allergy, especially to pollen, should not eat flowers. Shake flowers to encourage insects to leave, then dip them in cold salt water (RHS). The ASPCA lists Calendula officinalis as non-toxic to dogs and cats, but French and African marigolds (Tagetes) are a different plant whose sap can irritate, so check which marigold you have before pets chew it.

Verdict

Calendula earns a place in a Scottish vegetable garden as a hardy, site-tolerant annual with edible petals that feeds pollinators and predatory insects. Deadhead it to keep it flowering and stop it seeding everywhere. For protecting tomatoes and brassicasThe cabbage family: cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi, swede, turnip and more, sharing the same pests, diseases and rotation rules. Full definition →, rely on netting, fleeceA lightweight, breathable fabric laid or draped over plants to trap a little warmth and keep off frost, wind and some flying pests. Full definition → or resistant varieties; calendula is a bonus, not a defence.

Common questions

Sources