Half-hardy annuals are quick to flower and provide a burst of colour in summer borders and pot displays. To give them 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. Half-hardy annuals are surprisingly easy to grow although you do need to raise them from seed. Growing them from seed will give you a much wider choice of varieties than you’ll have if you buy ready-grown plants, and some species will flower in as little as 12 weeks.
This video suggests nine half hardy annual flower varieties for growing in the cutting patch, to give you flowers to make 2-3 bunches a week from June to October.
This video shows you how to plant Cosmos seeds in a way that gives them the best conditions to germinate and grow.
How To Sow Half Hardy Annuals
- Fill a tray with seed compost, then sow a tiny pinch of seeds in each cell.
- Cover with vermiculite, water and place the tray in a propagator in a warm spot.
- Once seeds have sprouted, wait until two pairs of leaves form.
- Transplant each seedling into a 7cm 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, move the plants to a cold frame
or patio, bringing them in at night.
- After a week you can plant them outside.
Prick out seedlings into pots or multi-cell trays and grow them on into sturdy plants, ready to drop into border gaps. Cosmos, Nicotiana, Tagetes, Cleome, Zinnia and Nasturtium are all half-hardy annuals and you can dot single plants as accents through your borders, or plant generous drifts between perennials, providing a contrast of foliage and colour.