When to plant Cosmos in Perth

Sow seeds in trays or modules from 25th March to 18th April, using 0.5 cm of fine compost. Keep them at 18–21 °C and just moist, not wet.

Move seedlings on when they are large enough to handle, from 8th April to 16th May. Pot them into small pots and keep them growing in a bright, frost-free place.

Acclimatise plants over 15 days before planting out, from 9th May to 23rd May. Put them outside in the daytime at first, then leave them out for longer each day so they do not check in cold weather.

Plant into free-draining soil from 23rd May to 9th June, spacing plants 30 cm apart. Water in thoroughly straight after planting and protect young plants from slugs and late cold snaps if needed.

Remove fading flowers regularly from 22nd June to 9th October. This stops the plant setting seed too early and keeps it producing flowers until the autumn frosts. Tie in taller stems if the plants get blown about, and water during dry spells.