Three species, not three varieties
African, French or Signet? The three types of marigold are really three species, not three varieties of one plant. All three flower for months, all three bring bees and hoverflies in, and all three earn a spot beside vegetables. Height is the easiest way to tell them apart.
African marigolds, Tagetes erecta
African marigolds carry far more petals than the other two and are the tallest, usually 45 to 90cm. They are annuals. Plant them where they will not shade shorter crops: they are best planted on the south side of your vegetable garden, or in front of tall crops like corn. Two stocked types are Marigold Hawaii and African Crackerjack.
French marigolds, Tagetes patula
This is the marigold most gardeners picture: smaller at roughly 15 to 45cm, with looser petals in orange, yellow and maroon. They suit short crops such as zucchini and they intercrop between tomatoes well. Try Dwarf Double Red Cherry, Bonita Mixed or Sparky Mixed.
Signet marigolds, Tagetes tenuifolia
Signets carry small single flowers, five petals arranged like a star, on fine ferny foliage at 20 to 30cm. They are not as showy, but bees work them steadily and they grow happily among the others. Starfire Mixed is the Signet we stock.
Sowing and growing
Marigolds are among the easiest flowers to raise from seed. Sow direct into a forked over bed, or into punnets to plant out later. Cover the seed with 5 to 10mm of mix, keep it just moist, and expect seedlings in 5 to 10 days once the soil sits around 18°C. Space French and Signet plants 20 to 25cm apart and African plants 30 to 40cm. Give them at least six hours of sun. Ordinary soil suits them: a heavy nitrogen feed gives leafy plants and fewer flowers. Water at the base, and pinch out the tip of young plants for a bushier shape.
When to sow around Australia
- Temperate (Sydney, Melbourne, Newcastle, coastal New South Wales and Victoria, southern South Australia): September to January, or late August under cover.
- Mediterranean (Perth, south west Western Australia, Adelaide, the South Australian gulf country): the same September to January window, sown early so plants are established before the dry summer.
- Cool and alpine (Tasmania, Canberra, Ballarat, Armidale, the tablelands): October to December, or September in pots under cover.
- Subtropical (Brisbane, the Sunshine Coast, Bundaberg, Coffs Harbour, Lismore): June through to April.
- Tropical (Darwin, Cairns, Townsville, Broome, the Top End): March to September, through the dry season.
- Arid and semi-arid (Alice Springs, Broken Hill, Kalgoorlie, Mildura, most of the inland): late August to October, then February to March.
These are broad groupings. If you garden between two of them, or in hills above a warmer coast, your local frost dates beat any map.
What marigolds do in a vegetable garden
Marigolds sit well with many summer crops, including watermelon, potatoes, eggplants and corn, and the most common pairing is with tomatoes, which want the same warm, sunny, well drained conditions. How well each claim is supported varies, so take them one at a time.
Whitefly
This is the best supported claim. French marigolds release limonene into the air, and glasshouse trials found that interplanting them with tomatoes lowered whitefly numbers on the tomatoes. That work was done under glass, where the scent stays put, so expect less in an open bed.
Root knot nematodes
Marigolds can suppress root knot nematodes, but only when used the way growers use them. A few plants dotted between vegetables does not do it. A dense block of French marigolds sown across the whole bed, grown as a cover crop for two to three months, then cut down and dug in before the next crop, does. Species matters: Bonita Mixed and African Crackerjack are resistant, while Signets are susceptible and can build the population instead. Petite Series Harmony is often named for this job, and trials rate it resistant to Meloidogyne incognita and M. javanica, though only intermediate to susceptible against M. arenaria. Marigolds do little against the northern root knot nematode, M. hapla, which turns up more often in cooler districts.
Aphids
Aphids are drawn to yellow, and a yellow marigold planting may pull some away from a nearby crop. The evidence is thin, so treat it as a bonus rather than a plan, and check the plants weekly: an untended trap simply becomes an aphid nursery. The steadier return is the ladybirds, hoverflies and lacewings the flowers bring in.
Thrips, leaf miners and spider mites
All three feed on marigolds, which is why the flowers are sometimes offered as a sacrifice planting. There is a catch. Marigolds host tomato spotted wilt virus and thrips carry it, so a thrips colony on marigolds beside your tomatoes, capsicums or lettuce can move the virus into them. If spotted wilt has been a problem before, keep marigolds well away from those crops, and bin rather than compost any plant showing the bronze ringspots.
Eating the petals
Marigold petals are edible within limits. Signet petals are the ones grown for the kitchen, with a mild citrus flavour that suits a salad. African and French petals are edible but usually bitter, so they work better as a scatter of colour. The foliage is not eaten, the sap can irritate skin, and petals from a plant used as a trap or sprayed with anything should never go on a plate.
Deadheading
Marigolds ask for very little. The one job worth doing is deadheading: snip each flower off as it fades. Spent flowers hold moisture, which is where botrytis and other moulds usually start, and removing them keeps new buds coming.
Related growing guides
- Companion planting in Australia: what really helps, and what is folklore
- Root-Knot Nematode: The Hidden Cause of Wilting and Forked Roots
- Stop Growing Vegetables On Their Own: The Flowers That Bring The Bees Your Zucchini Needs
Ready to plant? Browse our Marigold Seeds.