Patch & Pot
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Lesson 2

Sow late, sow short

Sow late, sow short

Cosmos hate cold; sow indoors mid-April or direct outside late May (after last frost and once nights are above 10°C). Direct-sown plants are stronger; transplanted plants are earlier.

Pinch the leading shoot at 30 cm — non-negotiable — to make the plant bush rather than a leggy stick. This single move doubles your eventual flower count.

In pots: 1 dwarf plant per 5 L pot, or 3 per 15 L tub. In ground: 30 cm apart. Cosmos seedlings transplant willingly compared to most annuals — but never let them get pot-bound.

From seed to first flower

  1. 1Mid-April: sow 1 seed per 7 cm pot of seed compost, just covered.
  2. 2Germinate at 18–20°C — up in 5–7 days.
  3. 3Grow on cool and bright; pot up to 1 L if they outgrow first pot.
  4. 4Late May (after last frost): harden off 5 days, plant out 30 cm apart.
  5. 5At 30 cm tall: pinch the central growing tip — yes, even though it feels brutal.
  6. 6First flowers 8–10 weeks from sowing; carry on until first frost.
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