For the first few years, perennial plants should be kept in pots but never neglected – potting on is vital to ensure they’re never pot bound. While the plants are young, and the weather is cold, they’ll need protection to prevent their roots freezing. A garden cold frame is ideal.
When plants are growing strongly, and the weather is mild, it may be worth planting them out into a nursery bed. This can be just a strip of soil in the vegetable garden or a piece of border where they can grow on without too much competition. They’ll bulk up well and may even grow enough to divide after a year.
More seed sowing advice:
Find out more about these eight perennials to grow from seed.
Height x spread: 1m x 45cm.
Buy seeds, or collect from your best astrantia plants, they won’t all come true but you may get some with their parents’ traits. Surface sow under glass, cover with grit. If no germination occurs after two months, put outside in an exposed spot.
H x S: 90cm x 30cm.
H x S: 20cm x 20cm.
Geranium psilostemon is best grown from your own saved seed. Each seed is large, so sow individually into modules. Should germinate fairly rapidly. Pot on as plants bigger.
H x S: 1.2m x 1.2m.
Sow eryngium seeds thinly on the surface of the compost. Seed usually germinates quickly but may need a period of cold to spur it on. Prick out and pot on promptly and may you get a few flowers in the first year.
H x S: 45cm x 30cm.
Add grit to seed compost before sowing lavender seeds. Surface sow and cover with a centimetre of grit. After initial watering, don’t water again until the compost is dry. Prick out into gritty compost.
H x S: 1m x 1m.
Helleborus x hybridus
Collect your own hellebore seeds, as they soon lose viability. Sow individually into module trays, spacing out regularly. Stand trays outside until germination.
H x S: 45cm x 45cm.
Selinum wallichianum has very long-lasting umbels that improve each year. Sow fresh on the surface the compost. May need vernalisation (several months in cold, damp compost to break dormancy). Prick out promptly. Avoid disturbing roots.
H x S: 1.8m x 60cm.