Marigold Sowing and Growing Guide
Marigold growing guide
Marigolds are best sown in late spring because they are very tender plants and must not be transplanted outside until the last week of May or early June. Sowings can begin in late April and continue until late May.
A kitchen windowsill or a heated propagator is perfect for germination. You can use either a seed tray (with or without grids), or a few small pots – filled with a seedling specific compost. Make sure you moisten the compost before planting your seeds. Plant your seeds evenly apart from each other with at least 1cm between each seed and sprinkle with a dusting of compost on top. Cover the seeds with a plastic bag if they are on a windowsill – this will keep the conditions warm and moist. If your seeds are in a heated propagator this won’t be necessary.
Marigolds need to be kept warm in the germination period. A temperature between 16-18 degrees Celsius is optimum and seedlings can emerge as quickly as 5-7 days.
Prepare to transplant your seedlings after about 2 weeks. Your seedlings should have 2-3 leaves on them before you consider moving over to pots. 9cm pots are perfect for marigold seedlings, and they can stay in these for up to 5 weeks. Your marigolds will still not withstand being outside at this point and will need to be kept inside on either a windowsill, in a conservatory or moved into a greenhouse/cold frame. Plants can be moved outside into a non-heated greenhouse/cold frame before the mid-end of April but be aware that extra protection may be necessary if a night frost is forecast. Marigolds have no frost tolerance and will not survive in a non-heated greenhouse or a cold frame if there were a cold snap. Direct sowing in soil beds or pots outside is possible from late May and a good summer show is possible using this method.
Once your marigolds start to outgrow the pots, you can move them into their final position in the garden. Choose a sheltered sunny location if possible although they will prosper in most positions if they have adequate sunlight, i.e. not in the shade. ‘Firebird’ takes 8-10 weeks to flower but taller types can take 12-14 weeks before they bloom. Remove dead flowers to encourage continuous blooming from side branches and look forward to a colourful display for 10-12 weeks after first flowers develop. Marigolds can be very successful in large patio pots so it's well worth considering this option.