Perennial flowers from seed: starting, stratifying and timing
Perennials are slower than annuals: many take a season to establish and flower in their second year. Seed is the cheapest way to get a lot of plants, and many native perennials need a cold spell to germinate.
When to sow
Two reliable routes. Sow in late winter indoors, 6 to 10 weeks before the last frost, for plants that germinate without a chill. Or sow in autumn or winter in labelled pots outside, or directly in a prepared bed, and let the weather stratify the seed. Check the plant page: coneflower, milkweed, penstemon, baptisia and columbine differ.
Light, temperature and humidity
Many perennial seeds are tiny and need light, so press them onto the surface. Cover trays with a clear lid until emergence. Many germinate best in the mid-60s to mid-70s°F (roughly 18 to 24°C); exceptions are noted on each plant page.
Equipment and mix
Fine seed-starting mix, shallow trays or pots, labels, a clear dome and lights are enough. See the seed-starting guide for the full set-up.
Potting on and planting out
Perennial seedlings are slow; pot up when they have two or three true leaves, harden off, and plant out after frost. Expect small plants in year one and flowers in year two for many species.
Which seed to buy
Buy from catalogues that state the variety, sowing guidance and stratification needs. Named seed mixes give a quick border; single species give predictable results.
Plants in this guide
| Plant | Germination temp | Depth | Days | Light | Before sowing |
|---|---|---|---|---|---|
| Coneflower (Echinacea) Echinacea purpurea | 65 to 70°F | covered lightly | 10 to 28 | Either | Nothing needed |
| Black-eyed Susan Rudbeckia hirta | 68 to 72°F | cover very lightly | 7 to 14 | Needs light | Nothing needed |
| Columbine Aquilegia spp. | 70 to 75°F | do not cover | 10 to 28 | Needs light | Nothing needed |
| Milkweed Asclepias spp. | 65 to 75°F | cover or leave exposed | 14 to 28 | Either | Treat seed |
| Coreopsis (tickseed) Coreopsis spp. | 65 to 75°F | cover or leave exposed | 9 to 12 | Either | Nothing needed |
| Yarrow Achillea millefolium | 65 to 70°F | lightly covered or exposed | 10 to 15 | Either | Nothing needed |
| Penstemon (beardtongue) Penstemon spp. | 70 to 70°F | surface; do not cover | 7 to 21 | Needs light | Treat seed |
| Baptisia (false indigo) Baptisia australis | see page | covered | 7 to 14 | Either | Treat seed |
| Lupine Lupinus spp. | 65 to 75°F | ¼ in (6 mm) | 14 to 21 | Cover | Treat seed |
| Delphinium Delphinium spp. | 65 to 70°F | cover lightly | 10 to 20 | Either | Nothing needed |
| Hollyhock Alcea rosea | 70 to 70°F | lightly covered | 5 to 21 | Either | Nothing needed |
| Foxglove Digitalis purpurea | 65 to 70°F | see page | 10 to 21 | Nothing needed | |
| Catmint Nepeta spp. | 70 to 70°F | do not cover | 7 to 14 | Needs light | Nothing needed |
| Gaillardia (blanket flower) Gaillardia spp. | see page | surface | varies | Needs light | Nothing needed |
| Dahlia Dahlia × hybrida | 65 to 70°F | ¼ in (6 mm) | 3 to 5 | Either | Nothing needed |