Reference
Which Seeds Need Cold Stratification: 78 Common Garden Plants
Yes, optional, or no — for every plant people actually ask about, with the cold period each one wants and the thing that matters more than stratification when it is not needed.
By Sohail Akhtar · Published 14 September 2026
How to use this list
Most lists of this kind give you two columns: needs it, or does not. That is not how seed behaves. A large group in the middle germinates perfectly well without a cold period and simply comes up more evenly with one — and lumping those in with the true dormant species sends people to the refrigerator for a month they did not have to spend.
So there are three groups here. If you only read one thing, read the third column: for the great majority of seed that fails, the cause was sowing depth, light or temperature, not dormancy.
The method itself — damp medium, sealed bag, main body of the refrigerator at 1–5°C — is the same for every species in the first two groups and is set out step by step in our guide to cold stratifying seeds. This page is only about which seeds to put through it.
Seeds that need cold stratification (21)
Germination is unreliable, very slow, or fails outright without a cold, moist period. Skipping it is the usual reason a tray of these never comes up.
| Plant | Cold period | What actually matters |
|---|---|---|
| Milkweed (common) Asclepias syriaca | 4 weeks | Thirty days in the refrigerator is the single biggest lever on milkweed germination. Winter sowing outdoors in a vented container does the same job and is what most monarch programmes recommend. |
| Swamp milkweed Asclepias incarnata | 4 weeks | Same thirty days as common milkweed. It wants damper ground afterwards than the other asclepias, which is the part people miss. |
| Butterfly weed Asclepias tuberosa | 4 weeks | The taproot resents disturbance, so stratify and then direct sow, or start in deep cells and transplant early. |
| Echinacea (purple coneflower) Echinacea purpurea Full guide | 4 weeks | Germinates patchily in warm soil and reliably after four cold weeks. This is the species most often blamed on bad seed when the problem was dormancy. |
| Lavender Lavandula angustifolia Full guide | 3–6 weeks | Even stratified, lavender is slow and low-percentage from seed. Sow more than you need and expect three weeks to a month before anything shows. |
| Columbine Aquilegia spp. | 3–4 weeks | Needs light as well as cold, so surface sow after the cold period rather than burying it. |
| Delphinium Delphinium spp. | 2–4 weeks | Also wants darkness and cool soil to germinate. Fresh seed performs far better than old — delphinium loses viability quickly at room temperature. |
| Aster (perennial) Symphyotrichum spp. | 4 weeks | Perennial asters need the cold period. Annual China aster (Callistephus) does not, and the two get confused constantly. |
| Anise hyssop Agastache foeniculum | 4 weeks | Surface sow after stratifying — it needs light to germinate, so the cold period and the sowing depth are two separate requirements. |
| Bee balm / wild bergamot Monarda spp. | 4 weeks | Both the garden bee balm and wild bergamot want the same month of cold. Surface sow afterwards; the seed is tiny and needs light. |
| Marshmallow root Althaea officinalis Full guide | 3–4 weeks | Erratic without the cold period, and it wants genuinely damp ground afterwards rather than the sharp drainage most herbs prefer. |
| Hosta Hosta spp. | 4 weeks | Seed-grown hosta does not come true to the parent plant. If you want a named variety, divide it instead of sowing. |
| Larkspur Consolida ajacis | 1–2 weeks | Cold and darkness together. Autumn direct sowing is easier than the refrigerator for this one, because larkspur hates root disturbance. |
| Apple Malus domestica | 8–12 weeks | Seedlings will not resemble the fruit you took the pips from — apples do not come true from seed. Grow them for rootstock or curiosity, not for the same apple. |
| Peach Prunus persica | 12–16 weeks | Crack the hard outer stone carefully and stratify the kernel inside to cut the wait considerably. |
| Cherry Prunus avium | 12–20 weeks | The longest wait on this list. Start in autumn so the period finishes in time for a spring sowing. |
| Blueberry Vaccinium spp. | 8–12 weeks | Needs acidic growing medium after stratification, and several years to fruit. Named cultivars are far faster bought as plants. |
| Blue vervain Verbena hastata | 4 weeks | Not the same plant as the garden verbena further down this list, and unlike it, this one will not germinate at all without the cold. It needs light afterwards too — surface sow it.Measured: Germinated 100% in 3–5 days after a cold period followed by warmth in light, and none at all at 70°F without the cold. (Deno, on V. hastata) |
| Joe Pye weed Eutrochium purpureum | 4 weeks | One of the few daisy-family plants that genuinely needs the cold period — most of that family does not, which is why this one catches people out.Measured: Showed the cold-then-warm germination pattern, noted as unusual within the daisy family. (Deno, on Eupatorium purpureum) |
| Ironweed Vernonia noveboracensis | 4 weeks | Tall, late and worth the wait, but it will not shortcut the cold. Sow it in autumn outdoors if the refrigerator is full.Measured: Fresh seed gave 100% in 2–4 days after a cold period, against 5% at 70°F without one. (Deno, on V. noveboracensis) |
| Penstemon Penstemon spp. | 4–8 weeks | The western mountain species are the strict ones. Short-lived species that flower in their first year are much more relaxed about it.Measured: Most germinated largely at 40°F, and sowing at 70°F was often fatal or near fatal. (Deno, on Rocky Mountain perennial species) |
Seeds that benefit from it but do not require it (15)
These germinate without a cold period, but a short one makes the tray come through evenly instead of over several straggling weeks. Worth doing if you have the fridge space and the time; not worth delaying a sowing for.
| Plant | Cold period | What actually matters |
|---|---|---|
| Black-eyed Susan / rudbeckia Rudbeckia hirta | 4 weeks | Germinates without cold, but a month of it makes the tray come up evenly instead of over three straggling weeks. It also needs light, so do not bury it. |
| Shasta daisy Leucanthemum × superbum | 2–4 weeks | Will germinate warm. Cold mainly tightens up how evenly the tray comes through. |
| Blanket flower Gaillardia spp. | 2–3 weeks | Surface sow either way — it needs light, and that matters more than the cold period does. |
| Coreopsis Coreopsis spp. | 2–4 weeks | Perennial coreopsis responds to cold more than the annual types do. Both need light to germinate. |
| Foxglove Digitalis purpurea | 2–4 weeks | Dust-fine seed that must sit on the surface in good light. Every part of the plant is toxic — worth knowing before you put it where children or livestock go. |
| Poppy Papaver spp. | 1–2 weeks | A short chill helps, but autumn or late-winter direct sowing does the same job with no refrigerator. Poppies resent transplanting, so sow where they are to flower. |
| Scabiosa (pincushion flower) Scabiosa spp. | 2 weeks | Perennial scabiosa benefits; the annual types germinate readily warm with no cold at all. |
| Canterbury bells Campanula medium | 2–4 weeks | Biennial — a rosette in year one and flowers in year two, whatever you do about stratification. Surface sow; it needs light. |
| Forget-me-not Myosotis spp. | 2–3 weeks | Self-seeds so freely once established that most gardeners never stratify it twice. |
| Strawberry Fragaria × ananassa | 2–4 weeks | Cold improves an otherwise slow, uneven germination. Seed-grown plants will not match a named cultivar; runners will. |
| Cleome (spider flower) Cleome hassleriana | 1–2 weeks | A brief chill, or fluctuating day and night temperatures, both break its light dormancy. It needs light too. |
| Hardy hibiscus Hibiscus moscheutos | 2–4 weeks | The hard coat matters more than the cold. Nick or soak the seed first. Tropical hibiscus needs neither treatment. |
| Hyssop Hyssopus officinalis | 2–4 weeks | Germinates warm without help. A short cold period evens it out. Do not confuse it with anise hyssop, which genuinely needs the month. |
| Evening primrose Oenothera biennis Full guide | 2–4 weeks | Direct sown in autumn, the winter does this for you. Biennial, so year one is a leaf rosette and year two is flowers. |
| Goldenrod Solidago spp. | 4 weeks | The answer changes with the age of your seed. Fresh autumn-collected seed wants the cold period; the same seed after a few months in a dry drawer often does not.Measured: Fresh seed needed the cold period. The same seed after six months of dry storage germinated warm without it. (Deno, on S. caesia) |
Seeds that need no cold period at all (42)
A cold period gains you nothing here and costs you weeks. Where these fail it is almost always sowing depth, light or temperature — not dormancy.
| Plant | Cold period | What actually matters |
|---|---|---|
| Lupine Lupinus spp. | None | The barrier is a hard, water-impervious seed coat, not dormancy — so nick it with a file or soak it overnight. Chilling an unscarified lupine seed does nothing, which is why it disappoints so many people who followed a stratification list.Measured: Seed germinated 100% on the fifth day when a hole was ground through the coat, and not at all otherwise. (Deno, on L. lepidus, L. lyallii) |
| Snapdragon Antirrhinum majus | None | A light problem, not a cold one. Surface sow and keep it bright and cool. Sowing it at refrigerator temperature only slows it down.Measured: A classic warm germinator: dry-stored seed germinated 90% on the third day at 70°F. (Deno, on A. majus) |
| Zinnia Zinnia elegans | None | A warm-season annual with no dormancy at all. It wants warm soil, not cold seed — sow after your last frost and it is up in under a week. |
| Marigold Tagetes spp. | None | Germinates in a few days at room temperature. Chilling it wastes a month and gains nothing. |
| Cosmos Cosmos bipinnatus | None | No dormancy. Rich soil gives you tall leafy plants and few flowers, so sow it somewhere poor. |
| Sunflower Helianthus annuus | None | Direct sow after frost. The real threat is birds and mice taking the seed, not dormancy. |
| Hollyhock Alcea rosea | None | Commonly assumed to need cold because it is a cottage-garden biennial, but it germinates readily at ordinary room temperature in one to two weeks. Sow shallowly and keep it warm. |
| Bachelor's buttons (cornflower) Centaurea cyanus | None | Needs darkness rather than cold, so cover the seed. Direct sows happily in autumn or early spring. |
| Yarrow Achillea millefolium Full guide | None | Needs light, not cold. Surface sow and never bury it — burying yarrow is the usual reason a tray comes up empty and gets blamed on dormancy. |
| Calendula Calendula officinalis Full guide | None | The opposite requirement to yarrow: it needs darkness, so sow it about 6mm deep. No cold treatment at all. |
| German chamomile Matricaria chamomilla Full guide | None | Surface sow for light. Roman chamomile behaves the same way — neither wants a cold period. |
| Feverfew Tanacetum parthenium Full guide | None | Germinates readily at room temperature. It needs light, so press it onto the surface rather than covering it. |
| California poppy Eschscholzia californica Full guide | None | Direct sow only — it forms a taproot and dies if transplanted. Cool soil suits it, but that is a sowing date, not a stratification requirement. |
| Chicory Cichorium intybus Full guide | None | Direct sow for the taproot. Check your local weed list first — chicory has naturalised widely. |
| Nasturtium Tropaeolum majus | None | Soak the large seed overnight instead. Poor soil gives more flowers and fewer leaves. |
| Morning glory Ipomoea spp. | None | A hard seed coat, not dormancy. Nick it with a file or soak it overnight and it comes up fast. |
| Sweet pea Lathyrus odoratus | None | Another coat problem mistaken for dormancy. Soak or nick the seed. Autumn sowing under cover gives stronger plants, but that is a head start, not stratification. |
| Petunia Petunia × atkinsiana | None | Dust-fine seed that needs light and warmth. Surface sow and do not let it dry out. |
| Pansy / viola Viola × wittrockiana | None | Wants darkness and cool — not cold — soil to germinate. Cover the seed and keep it around 18°C. |
| Sweet alyssum Lobularia maritima | None | Surface sow for light. Germinates in under a week at room temperature and self-seeds thereafter. |
| Verbena Verbena spp. | None | Needs darkness and patience — germination is slow and uneven, but cold does not fix it. |
| Celosia Celosia argentea | None | A heat lover. Sow into warm soil after frost; cold treatment only delays it. |
| Gomphrena (globe amaranth) Gomphrena globosa | None | Warm-season annual. Soaking the fluffy seed overnight helps more than any cold period would. |
| Strawflower Xerochrysum bracteatum | None | Needs light to germinate. Surface sow into warm compost after the last frost. |
| Dahlia (from seed) Dahlia spp. | None | Seed-grown dahlias germinate warm in about a week and will not come true to a named parent. Tubers do. |
| Tomato Solanum lycopersicum | None | Wants heat, around 21–27°C. Cold seed is the opposite of what it needs. |
| Basil Ocimum basilicum | None | One of the most cold-sensitive things in the garden at every stage. Sow warm, plant out late. |
| Cilantro / coriander Coriandrum sativum | None | Direct sow — it bolts if root-disturbed. Crushing the round husk into two halves speeds germination. |
| Dill Anethum graveolens | None | Direct sow for the taproot and give it light; dill germinates better uncovered. |
| Parsley Petroselinum crispum | None | Famously slow — three to four weeks is normal and gets mistaken for dormancy. Soaking overnight helps; cold does not. |
| Oregano Origanum vulgare | None | Tiny seed that needs light. Surface sow and keep it warm. |
| Sage Salvia officinalis | None | Germinates warm in one to three weeks. Some ornamental salvias do want cold — culinary sage does not. |
| Rosemary Salvia rosmarinus | None | Slow and low-percentage from seed, but cold is not the fix. Cuttings root easily and are how most people propagate it. |
| Thyme (and creeping thyme) Thymus spp. | None | Needs light. Surface sow it, keep it warm, and be patient — two to three weeks is normal. |
| Chives Allium schoenoprasum | None | Germinates warm in one to two weeks. Use fresh seed — allium seed loses viability faster than most. |
| Lemon balm Melissa officinalis | None | Needs light, so surface sow. It spreads hard once established — a container is worth considering. |
| Borage Borago officinalis | None | Direct sow and cover — it wants darkness. Self-seeds enthusiastically forever after. |
| Blazing star Liatris spicata | None | Widely sold as a seed that needs chilling. It does not — though the corms are so cheap that most people never sow it from seed at all.Measured: Dry-stored seed germinated 100% at 70°F, with light making no difference. (Deno, on L. spicata) |
| False indigo Baptisia australis | None | This one appears on extension lists as requiring stratification, which is worth knowing about before you spend a month on it. Deep taproot, so sow it where it will stay.Measured: Germinated 90–95% at 70°F using fresh seed or seed dry-stored six months, and notching the coat did not significantly help. (Deno, on B. australis) |
| Dianthus / sweet William Dianthus spp. | None | Reliable warm, and one of the easier perennials to raise from seed. Sweet William is a biennial, so expect the flowers in its second year.Measured: Fresh or dry-stored seed germinated in 1–4 weeks at 70°F. (Deno, on all species studied except D. armeria) |
| Bellflower Campanula spp. | None | Most of the genus needs no cold, but it is a big genus and a few do. Surface sow — the seed is fine and wants light.Measured: Most species germinated warm without a cold period; a minority needed cold first, and C. americana needed cold followed by light. (Deno, on numerous species) |
| Love-in-a-mist Nigella damascena | None | A hardy annual that resents root disturbance, so direct sow it where it is to flower. Autumn sowing gives bigger plants than a spring start. |
The three mistakes that get blamed on dormancy
Nearly every tray that fails gets put down to dormancy. In practice three other things account for most of it, and all three are visible in the table above.
Sowing a light-germinating seed too deep. Yarrow, chamomile, feverfew, snapdragon, bee balm, foxglove, columbine and black-eyed Susan all need daylight on the seed. Cover them and nothing happens, stratified or not. Press them onto the surface instead.
Sowing a dark-germinating seed on the surface. The opposite error, and calendula, larkspur, pansy and bachelor's buttons are the usual victims. These want covering.
Treating a hard seed coat as dormancy. Sweet pea, morning glory, nasturtium, lupine and hardy hibiscus are not waiting for winter — water cannot get in. Nick the coat with a file or soak the seed overnight and they germinate quickly. A month in the refrigerator does nothing for any of them.
Once the sowing itself is right, the timing question is the next one, and it is species-specific too — our frost-date planting calculator works backwards from your own last frost to tell you the week to start each cold period.
Where these answers come from
Most of this table is settled horticultural practice, and we say so rather than dressing it up as something we measured.
11 rows are different. Those carry a Measured note, and they come from Seed Germination Theory and Practice by Norman C. Deno (2nd edition, 1993) — a record of germination trials run across thousands of species, placed in the public domain and hosted by the USDA National Agricultural Library. Anyone can download it and check a row against the original.
That research is the reason a few entries here disagree with lists you will find elsewhere. Snapdragon germinated 90% on the third day at room temperature. Lupine did not germinate at all until its seed coat was physically breached, and then it managed 100% in five days — the cold was never the variable. False indigo, which some extension pages file under “requires stratification”, germinated 90–95% warm.
One caution we apply to ourselves: a finding covers the species actually tested, named in each note, and does not automatically extend to a whole genus. Deno's Aster samples were Eurasian alpines, which is why the North American perennial asters are still listed above as needing the cold period on the strength of ordinary practice instead.
Frequently asked questions
Do hollyhocks need cold stratification?
No. Hollyhock germinates readily at ordinary room temperature, usually in one to two weeks, and a cold period gains you nothing. It gets assumed otherwise because it is a hardy cottage-garden biennial, but the seed itself carries no cold dormancy. Sow it shallowly, keep it warm, and it will come up.
Do zinnia seeds need cold stratification?
No. Zinnia is a warm-season annual with no dormancy mechanism at all — it wants warm soil, not cold seed. Sow it after your last frost date and it will usually be up within five to seven days. Chilling it only delays the sowing.
Does yarrow need cold stratification?
No. Yarrow needs light to germinate, not cold. Surface sow it and press it down rather than covering it — burying yarrow seed is the usual reason a tray comes up empty, and the failure gets blamed on dormancy when the seed simply never saw daylight.
Do milkweed seeds need cold stratification?
Yes. Thirty days of cold, moist storage is the single biggest lever on milkweed germination, and that applies to common milkweed, swamp milkweed and butterfly weed alike. Winter sowing outdoors in a vented container does the same job without using fridge space, which is what most monarch habitat programmes suggest.
Does echinacea need cold stratification?
Yes. Echinacea germinates erratically in warm soil and reliably after about four weeks of cold, moist storage. This is the species most often blamed on bad seed when the real problem was dormancy. Autumn sowing outdoors achieves the same result without a refrigerator.
Does lavender need cold stratification?
Yes — three to six weeks. Lavender is slow and low-percentage from seed even when you do everything right, so sow more than you think you need and expect three weeks to a month before anything shows above the compost. Most nurseries propagate it from cuttings for exactly this reason.
Do marigold seeds need cold stratification?
No. Marigolds germinate in a few days at room temperature and have no cold requirement whatsoever. A month in the refrigerator costs you a month of the growing season and changes nothing about the result.
Do cosmos need cold stratification?
No. Cosmos is a warm-season annual with no dormancy. Sow it after frost into poor or average soil — rich soil gives you tall leafy plants and very few flowers, which is the mistake worth worrying about instead.
Do poppy seeds need cold stratification?
It helps, but it is not required. A week or two of cold improves germination for most Papaver species, and sowing in autumn or late winter directly where the plants are to flower does the same thing with no refrigerator involved. Poppies resent transplanting, so direct sowing is the better habit regardless.
Do black-eyed Susan seeds need cold stratification?
Not strictly, but four weeks of cold makes a visible difference. Rudbeckia will germinate without it and then come through over three straggling weeks; stratified seed comes up evenly. It also needs light, so surface sow it either way.
Do snapdragons need cold stratification?
Usually not — snapdragon is mostly a light problem rather than a cold one. Surface sow it, keep it bright and on the cool side, and it germinates without any chill. A brief cold period is sometimes recommended and does no harm, but most growers skip it entirely.
Does calendula need cold stratification?
No. Calendula needs darkness rather than cold, so sow it about 6mm deep and cover it. It is among the easiest seeds there is, germinating in one to two weeks at room temperature with flowers roughly six to eight weeks later.
Does chamomile need cold stratification?
No. German chamomile needs light to germinate, so surface sow it and never bury it. Roman chamomile behaves the same way. Neither wants a cold period, and giving one costs weeks for no gain.
Does bee balm need cold stratification?
Yes — about four weeks. Both garden bee balm and wild bergamot want the cold period, and both need light afterwards, so surface sow the tiny seed rather than covering it. That combination trips people up: they stratify correctly and then bury the seed.
Do columbine seeds need cold stratification?
Yes — three to four weeks. Columbine also needs light, so sow it on the surface after the cold period rather than burying it. Established plants self-seed freely afterwards, which means you generally only do this once.
Do sunflower seeds need cold stratification?
No. Sunflowers have no dormancy and germinate quickly in warm soil. Direct sow after your last frost. The real threat to a sunflower sowing is birds and mice taking the seed, not a failure to germinate.
Do strawberry seeds need cold stratification?
It helps. Two to four weeks of cold improves an otherwise slow and uneven germination. Worth knowing before you start: seed-grown strawberries will not match a named cultivar, whereas runners taken from an existing plant will.
How long do seeds need to be cold stratified?
Four weeks covers most temperate perennials, including echinacea, milkweed and bee balm. Lavender does better with three to six. Tree and fruit seeds are in a different league — apple wants eight to twelve weeks and cherry can want twenty. Check the species rather than applying one number to everything.