A packet of marigold seeds can fill gaps in summer containers and give a vegetable patch a useful splash of colour. But the word marigold can refer to two different groups of plants. French and African marigolds are Tagetes, commonly grown as tender summer bedding. Pot marigolds are Calendula, which generally cope with cooler conditions and may be sown at different times.
Check the botanical name on the packet before choosing a sowing date. This guide focuses mainly on growing Tagetes from seed, with notes on how Calendula differs.
Decide which marigold you're sowing
French marigolds, often labelled Tagetes patula, are typically compact plants with yellow, orange or red-toned flowers. African marigolds, Tagetes erecta, can grow taller and carry large, showy blooms.
Calendula officinalis is a different plant. Its flowers are often orange or yellow, but its seeds are curved rather than slender Tagetes seeds. Calendula is frequently sold as pot marigold and can be grown in cooler parts of the season.
Look at the height on the packet as well as the name. A low border edging plant and a tall cutting variety need different spacing, despite sharing a common name.
Sow Tagetes indoors for an earlier display
In Britain, sowing Tagetes indoors in spring gives you strong seedlings ready for planting after the last frost. The timing should suit the warmth and space you can provide. An early sowing in a cold, dark room rarely produces better plants than a slightly later sowing with adequate light.
Fill a clean seed tray or small modules with suitable peat-free seed compost. Firm the compost lightly and water so it is evenly moist, not saturated.
Sow the seeds thinly on the surface, following the packet's covering depth. Many Tagetes seeds are long and narrow; don't push them several centimetres into the compost simply because they're larger than basil seed. Use the supplier's specific sowing instructions.
Give seedlings warmth and light
Place the tray somewhere warm and bright. A propagator may help if your home is cool, but it is not essential where conditions are suitable. Check that the compost remains gently moist while seeds germinate.
As soon as seedlings appear, give them plenty of daylight. A tray left in a warm dark room can produce pale stems that collapse under their own weight.
Turn trays if all the seedlings lean strongly towards one side of the window. Ventilate covered trays to avoid excessively damp conditions, and remove covers when seedlings are established.
Move seedlings into individual pots
Once seedlings have developed their first true leaves and are large enough to handle, gently lift them from a shared tray and place them into small modules or pots.
Hold each seedling by a leaf rather than squeezing the fragile stem. Use a dibber to lift the roots with a little surrounding compost, then set the seedling into a prepared hole.
Water gently after transplanting and keep plants bright and warm while they develop. Don't rush them into their final positions merely because you have run out of windowsill space.
Harden off before planting outside
Tagetes are vulnerable to frost. In much of the UK, they are planted outside around late May or early June when cold nights have passed.
Gradually expose nursery-grown plants to outdoor temperatures, wind and stronger light. Begin with a sheltered daytime position and bring them back under cover at night. Increase the length of time outdoors over a week or two.
A sudden cold snap can set tender marigolds back considerably. Delay planting rather than expecting a little extra feed to repair frost damage.
Prepare the bed and decide on spacing
Tagetes generally prefer full sun and well-drained soil. Remove weeds, loosen compacted patches and check that the location won't sit under water after heavy rain.
Follow the spacing printed on the packet. Compact French marigolds can sit closer together than large African marigolds. Allow room for their mature canopy and for air to circulate between leaves.
Make planting holes that match the rootballs. Set each plant at the same level as its nursery pot, firm gently and water it in. Avoid covering the lower stems with extra compost simply to make a leggy plant look sturdier.
Planting marigolds in containers
A broad pot or window box can hold several compact marigolds, provided the container has drainage holes and enough compost for the roots.
Use a suitable peat-free multipurpose compost and position the container in sunshine. Arrange the plants before planting, leaving space for their mature spread rather than packing young seedlings edge to edge.
Containers need regular moisture checks during dry weather. A pot that stands in a saucer of water after rain can cause problems, so let excess water drain away.
Can you sow Tagetes directly outdoors?
Direct sowing can work once the soil is warm and frost risk has passed, but it usually provides a later display than plants started indoors. Prepare a fine seedbed and sow to the packet's depth and spacing.
Keep the surface moist during germination and protect emerging seedlings from slugs where needed. Thin crowded plants while young, before roots and stems compete for space.
If your garden is exposed and has heavy clay, raising plants in modules may be more dependable than sowing into cold soil. The aim is strong seedlings, not winning a competition to sow first.
What about pot marigold seeds?
Calendula is usually less demanding of high temperatures than Tagetes. It can often be sown directly into prepared ground in spring or late summer, depending on the variety and local conditions.
Because Calendula and Tagetes are different plants, do not apply every Tagetes sowing instruction to Calendula without checking the packet. Seed shape, spacing, cold tolerance and plant habit vary.
If a packet only says 'marigold', check the Latin name printed in small type or the supplier's website before committing a whole border.
Keep flowers coming through summer
Deadhead spent Tagetes flowers regularly if you want a long display. Removing fading blooms directs the plant away from seed production and keeps the bed looking tidy.
Water during prolonged dry spells, especially where plants are in containers. Avoid overfeeding, which can produce leafy growth without necessarily improving flowering.
Look for slug damage on young leaves and remove badly deteriorated flowers after prolonged rain. Tagetes can remain attractive until autumn cold ends their season.
Problems after sowing or planting
No seedlings may indicate cold compost, old seed, excessive dryness or soggy conditions. Check the seed's stated germination requirements before sowing another packet.
Very tall weak seedlings usually need more light and better airflow. Pinching and planting deeply cannot completely rescue plants that have been stretched in dark conditions.
If outdoor plants collapse after a frosty night, cold damage is likely. Replace badly damaged tender plants once conditions improve rather than repeatedly watering a dead stem.
The rewarding part of growing marigolds is how much colour a small packet can deliver. Start with the correct type, give seedlings enough warmth and room, and wait until the garden is ready for them.