What's the difference between Calendula marigolds and Tagetes marigolds?

Two unrelated plants share the name. Calendula officinalis (pot marigold, English marigold) — hardy annual, clear yellow or orange daisy-like flowers, edible petals, traditional UK cottage-garden plant. Tagetes patula and T. erecta (French and African marigolds) — frost-tender annuals from Mexico, brighter and more varied colours, traditional bedding plants. Different family, different growing requirements; just confusingly the same name.

Do marigolds really help tomatoes?

Yes, but only Tagetes — and only against root-knot nematodes, a pest mostly affecting greenhouse tomato beds where the same soil has been used for years. Tagetes patula secretes alpha-terthienyl which kills the nematodes. The marigolds beside tomatoes general claim is partly true for greenhouse soil; less true outdoors where root-knot nematodes aren't a major UK problem. Calendula has no such effect.

Are calendula petals edible?

Yes — pluck the petals from open flowers and sprinkle on salads, rice, soups, or use to colour butter and cheese. They have a mild, slightly resinous flavour. The whole flower is edible but the centre disk gets bitter. Sometimes called poor man's saffron — colour without the cost.

When should I sow marigolds in the UK?

Calendula: March to April direct outdoors; can also be sown in autumn (September) for early flowers the following spring. Tagetes: late March to early May indoors in modules; plant out after the last frost (mid-May south, early June north). Don't sow Tagetes outdoors before mid-April; cold wet soil rots the seed.

Why are my marigolds not flowering?

Likely causes: too much shade (both species want sun for 6+ hours a day); over-feeding (rich soil pushes leaves at the expense of flowers); seed heads forming (deadhead religiously); or for Tagetes, planted out too early when nights were still cold (the check stays with the plant). They want lean, sunny, deadheaded conditions.

Do marigolds self-seed?

Calendula yes, prolifically — once you have it, you have it for the next several years from self-sown seedlings on bare soil each spring. Tagetes barely — fresh sowing each year is the norm. Calendula self-seedlings often grow more vigorously than nursery-sown plants and crop earlier.

Œillet d’Inde (Tagetes)

Tagetes patula

Sow marigold seed direct outdoors from March onwards, or in modules from February — the name marigold covers two unrelated plants in UK gardens. Calendula officinalis (pot marigold, English marigold) is a fully hardy annual (RHS H4) with edible petals that self-seeds happily across British gardens. Tagetes patula (French marigold) and T. erecta (African marigold) are frost-tender annuals (RHS H1c) usually grown for summer bedding and tomato companion-planting in greenhouses. Both are easy, prolific and reliable. Calendula in clear yellow and orange; Tagetes in fiery orange, yellow and mahogany. Tagetes suppresses root-knot nematodes in greenhouse tomato beds. Both attract pollinators and hoverflies that prey on aphids — useful allies for the wider veg patch.

View full growing guide →