Grow the border’s tarty barmaids from seed
The big show-stoppers in the annual garden are, more often than not, half-hardy types, like these lovely Cosmos – more tips on growing them here.
Sometimes they’re tender perennials, like dahlias – more on growing them here – you can usually spot them, as they’re the ones being sold as plug plants in catalogues and garden centres, costing a small fortune.
They all need a long season to flower well, which means indoor sowing in a propagator sometimes as early as January (Antirrhinums), but more usually February/March.
What is critical here is light intensity. If you don’t have a brightly-lit place indoors, wait until March. Warmth and poor light will lead to leggy, weak seedlings which will easily fall victim to disease.
Propagator’s a good buy
A propagator with a constant temperature is a good buy too – here’s my guide on the best buys. Bear in mind how much plug plants cost, and it will soon pay for itself.
What they all need is good seed compost – buy the best you can afford. Some people like to cover seeds with Vermiculite or Perlite instead of compost – use what you know best. (I find the latter two don’t form a crust which is hard to wet, which is why I use them).
Make sure the soil is watered before you sow and doesn’t dry out. Sealing trays/pots in cheap freezer bags work well.
There’s a lot of old bedding favourites here – this is a quick guide to their germination temperatures; sowing depth; days to germination; and any special instructions.
Potted guide: half-hardy annuals
- Ageratum: 15-18ºC, surface sow, 10-15 days, don’t exclude light.
- Antirrhinum (Snapdragon): 20-25ºC, surface sow, 10-21 days, don’t exclude light.
- Busy Lizzie (Impatiens): 21-24ºC, fine sprinkling compost, 14-21 days, don’t exclude light.
- Cosmos: 18-25ºC, 3mm, 7-15 days, don’t exclude light.
- Dahlia: 20-30ºC, 6mm, 7-21 days, don’t exclude light.
- French/African marigold (Tagetes): 21-24ºC, fine sprinkling of compost, 7-21 days, don’t exclude light.
- Gazania: 18-25ºC, fine sprinkling compost, 14-30 days, don’t exclude light.
- Heliotrope (Cherry Pie): 20-25ºC, 1.5mm, 14-21 days, lowering temperature at night helps germination.
- Lobelia: 18-24ºC, surface sow, 14-21 days, don’t exclude light.
- Mesembryanthemum (Livingstone daisy): 15-20ºC, surface sow, 15-21 days, don’t exclude light.
- Nemesia: 13-15ºC, surface sow, 7-21 days, don’t exclude light, keep soil temperature below 19C.
- Nicotiana (tobacco plant): 21ºC, surface sow, 10-20 days, don’t exclude light.
- Osteospermum: 15-18ºC, fine sprinkling compost, 10-15 days, don’t exclude light.
- Petunia: 21-27ºC, surface sow, 10-21 days, don’t exclude light.
- Phlox drummondii: 18-20ºC, surface sow, 10-21 days, don’t exclude light.
- Rudbeckia: 20-25ºC: fine sprinkling compost, 7-21 days, don’t exclude light.
- Salvia splendens: 21-24ºC, surface sow, 10-14 days, leave in a shady spot for 24-48 hrs; then cover seed lightly.
- Verbena x hybrida: 24-27ºC, surface sow, 14-21 days, don’t exclude light.
- Zinnia: 20-25ºC, 1.5mm, 10-24 days, sow individually in 7.5cm pots.
Single not double dahlias
I’m not really a fan of the big show dahlias, but I do love the simpler, single types, such as Bishop of Llandaff, with its dark foliage and striking red flowers – ideal for a sunny, hot-themed border.
Bees and insects can’t get to the nectar in double flowers – another reason to grow singles.
You can buy tubers, but if you like a riot of colour and growing from seed, try Bishops Children (I bet the Church wasn’t happy about that name).
They are half-hardy perennials but are usually grown as annuals. You can lift the tubers in autumn for next year. I did this – they do survive well in a frost-free place.
They need a long growing season, hence the early sowing, but will flower until the first frosts.
Sow 0.6cm deep in trays and cover with compost, Vermiculite or Perlite. They should germinate in 7-21 days – don’t exclude light.
My packet cost £2.49 (40+ seeds) – the cheapest Bishop of Llandaff SINGLE tuber I could find was £3.25, ranging up to £9.99 for a potted plant.
Antirrhinums from seed
Cottage garden favourites Antirrhinums or snapdragons, are a half-hardy perennial but are best grown as an annual – which means an early start.
Sow seeds January-March, thinly, in trays of seed compost.
Don’t cover the seeds, or exclude light, as this helps germination. Keep moist and maintain a temperature of 18-22°C (64-72°F). Germination should take 10-29 days but may be erratic.
The seedlings are tiny – don’t be put off if they seem to be making little progress – I always think they’re going to die young.
Seeds can be sown July-September in a cold frame for planting out the following spring, but that’s too nerve-wracking for me.
When they are large enough to prick out, transplant them 5cm apart in seed trays ( or I use small modules) and grow on. Gradually acclimatise the plants to outside conditions before planting out 12-25cm apart (depending on the size of the variety) in a sunny position.
Potted guide: Antirrhinums
- Sow: January-March or July-Sept.
- Flowering: June-October.
- Position: full sun.
- Hardiness: Although half-hardy perennial, treat as a half-hardy annual.
- Recommended varieties: Available in dwarf, intermediate, tall and trailing. Tall: Royal Bride; Purple Twist, Chantilly Bronze (up to 90cm/36in). Intermediate: Tootsie F1, Black Prince; Day and Night, 45cm/18in. Dwarf: Bronze Dragon 30cm/12in.