Half-hardy annuals provide a burst of colour in summer borders and containers. To allow as long a flowering season as possible, sow seed early so that plants have plenty of time to establish before planting out. Once risk of frost has passed, plant your home-sown plants outside. Many varieties sown indoors by March or April will start to flower as early as June.
Fill a tray with seed compost, sow a tiny pinch of seeds in each cell and cover with vermiculite.Â Water and place the tray in a propagator in a warm spot.
Once seeds have germinated and two pairs of leaves formed transplant each seedling into an 8cm pot filled with sieved multi-purpose compost.
Water well after transplanting and keep the pots in a warm, bright place. Avoid exposure to bright sunlight, which can scorch the young leaves.
When all risk of frost has passed, harden off the plants by moving to a cold frame or patio, bringing them in at night. After a week they can be planted outside.