Zinnia flowers

How to sow zinnia seeds indoors

We show you how to sow zinnias indoors if too chilly to do so outdoors.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
At its best
At its best

Plant is not at its best in January

Plant is not at its best in February

Plant is not at its best in March

Plant is not at its best in April

Plant is not at its best in May

Plant is not at its best in June

Plant is at its best in July

Plant is at its best in August

Plant is at its best in September

Plant is at its best in October

Plant is not at its best in November

Plant is not at its best in December

To do
To do

Do not To do in January

Do To do in February

Do To do in March

Do To do in April

Do not To do in May

Do not To do in June

Do not To do in July

Do not To do in August

Do not To do in September

Do not To do in October

Do not To do in November

Do not To do in December

Zinnias are wonderfully versatile plants. Not only can they be used in borders to fill gaps or to transform patches of bare soil, they’re also available in a dazzling array of colours.

By sowing zinnia seeds early in the year, you can enjoy riotous colour from midsummer until the first frosts.

Zinnias also make beautiful cut flowers. Try growing other cut flowers from seed to ensure you have an abundant supply of flowers for the house.

Don’t worry if you don’t manage to sow them indoors by April – zinnias can be sown outdoors in May and June.

Discover how to sow zinnia seeds indoors by following our four simple steps, below.

By sowing zinnia seeds early in the year, you can enjoy riotous colour from midsummer until the first frosts.

You will need

  • Seed compost
  • Zinnia seeds
  • 6cm pots or seed trays
  • Vermiculite or horticultural sand
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Step 1

Fill small plastic pots or a seed tray with seed compost and water it gently. Place the seed on the damp compost, allowing around eight seeds per 9cm pot.

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Step 2

Lightly firm the seeds in place using the base of an empty pot, then cover the seeds with a fine layer of vermiculite, horticultural sand or more seed compost.

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Step 3

Water the pot of seeds carefully and allow excess water to drain off before placing pots or trays on a warm windowsill or in a heated propagator at 20-25°C.

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Step 4

Prick out seedlings when they’ve formed two pairs of leaves, growing on in their own pot. Harden off and plant out 30cm apart when all risk of frost has passed.

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Planting out your zinnias

When planting out your zinnias, choose a site for them that is sunny and sheltered, and plant them in well-drained soil.