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Seed Stratification Reference Chart
Quick guide to which seeds need cold treatment before germination
A practical reference for Canadian gardeners starting seeds indoors or using winter sowing methods.
Quick tip: If a plant naturally drops seed outdoors in Canada and comes back in spring, it likely benefits from cold stratification.
Stratification Requirements
| Plant | Type | Stratification | Duration | Notes |
|---|---|---|---|---|
| Milkweed | Perennial | Yes | 30–60 days | Cold moist required |
| Columbine | Perennial | Yes | 30 days | Native woodland species |
| Echinacea purpurea | Perennial | Sometimes | 2–4 weeks | Improves germination rate |
| Lupine | Perennial | Yes | 30 days | Scarification recommended |
| Delphinium | Perennial | Yes | 2–4 weeks | Cold sensitive germination trigger |
| Black-eyed Susan | Perennial/Biennial | Sometimes | 30 days | Varies by seed source |
| Tomato | Annual | No | — | Start indoors warm |
| Peppers | Annual | No | — | Require warm soil |
| Sunflower | Annual | No | — | Direct sow recommended |
Quick Facts
- Cold stratification mimics winter conditions for seeds.
- Many native perennials require cold exposure before sprouting.
- Winter sowing is a natural form of stratification outdoors.
- If a plant naturally self-seeds and comes up in spring, its seeds may need cold stratification, a period of cold, moist conditions, before they will germinate. Hollyhocks and Delphiniums are one example. In my Zone 6 garden, I often let them self-seed and allow winter to do the work rather than starting them indoors.
Hollyhocks: winter can provide the cold stratification some seeds need.
Sunflowers: direct sowing can produce sturdier plants than starting them indoors. Indoors they are often leggy. Letting critters sow sunflowers in the fall works for me as well. I just transplant them wherever I need them to be.
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