Guide

What to Winter Sow, and What Is Just a Wasted Jug

Every winter sowing list names the same seeds without saying why. The why is simple — winter sowing is cold stratification done outdoors — and once you know it, you can work out any seed for yourself. Here it is applied to 78 plants.

By Sohail Akhtar · September 2026

What winter sowing actually does

You cut a translucent milk jug most of the way round, fill the base with compost, sow, tape it shut, take the cap off, and stand it outside in the middle of winter. It looks like neglect. It is actually a small unheated greenhouse: light gets in, rain and snow get in through the vent, moisture stays, and the seed inside still feels every freeze and thaw.

That freezing and thawing, with the seed damp the whole time, is cold stratification. It is the same treatment as a month in the refrigerator in a bag of sand, delivered by the weather instead. Which tells you exactly which seeds are worth doing it to: the ones that need a cold period before they will germinate at all.

So the list below is not a list of favourites. It is our cold stratification reference for 78 species sorted by what the winter can do for each one — plus the one thing those lists leave out, which is that 13 of the plants people put in jugs every January are killed by frost and were never candidates at all.

Rows of seedling trays standing outdoors at a forestry nursery under several inches of snow, the seedlings still green where the snow has not covered them. — Nursery seedling trays overwintering outdoors under snow. Forestry nurseries have raised stock this way for decades, for the same reason winter sowing works in a jug on a doorstep — the cold is doing something useful.Photo: USDA Forest Service, Pacific Southwest Region 5 (Public domain)

Seeds the winter does the work for (21)

These need a cold, moist period. Winter sowing is the least effort way to give it to them, and for the trees and shrubs at the end of the list — which want two to five months — it is far easier than keeping a bag in the refrigerator until spring.

Seeds that need a cold period, which winter sowing supplies
Plant	Cold it wants	What to know
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.
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.
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.
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.

Seeds it helps, without being essential (15)

These germinate without cold, but a spell of it makes a tray come through evenly instead of over three straggling weeks. Worth a jug if you have the space; not worth holding a sowing back for.

Seeds that germinate more evenly after cold, without requiring it
Plant	Cold it wants	What to know
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.

Hardy seeds worth a jug for an earlier start (29)

Nothing here has dormancy to break, so the cold is not doing any germinating work. What these have in common is that frost does not bother them, so a jug outdoors gets you plants weeks before an indoor sowing would — without a windowsill, a heat mat or a light.

Hardy seeds with no cold requirement, worth sowing early anyway
Plant	What to know
Lupine Lupinus spp.	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.
Snapdragon Antirrhinum majus	A light problem, not a cold one. Surface sow and keep it bright and cool. Sowing it at refrigerator temperature only slows it down.
Hollyhock Alcea rosea	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	Needs darkness rather than cold, so cover the seed. Direct sows happily in autumn or early spring.
Yarrow Achillea millefolium Full guide	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	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	Surface sow for light. Roman chamomile behaves the same way — neither wants a cold period.
Feverfew Tanacetum parthenium Full guide	Germinates readily at room temperature. It needs light, so press it onto the surface rather than covering it.
California poppy Eschscholzia californica Full guide	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	Direct sow for the taproot. Check your local weed list first — chicory has naturalised widely.
Sweet pea Lathyrus odoratus	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.
Pansy / viola Viola × wittrockiana	Wants darkness and cool — not cold — soil to germinate. Cover the seed and keep it around 18°C.
Sweet alyssum Lobularia maritima	Surface sow for light. Germinates in under a week at room temperature and self-seeds thereafter.
Verbena Verbena spp.	Needs darkness and patience — germination is slow and uneven, but cold does not fix it.
Cilantro / coriander Coriandrum sativum	Direct sow — it bolts if root-disturbed. Crushing the round husk into two halves speeds germination.
Dill Anethum graveolens	Direct sow for the taproot and give it light; dill germinates better uncovered.
Parsley Petroselinum crispum	Famously slow — three to four weeks is normal and gets mistaken for dormancy. Soaking overnight helps; cold does not.
Oregano Origanum vulgare	Tiny seed that needs light. Surface sow and keep it warm.
Sage Salvia officinalis	Germinates warm in one to three weeks. Some ornamental salvias do want cold — culinary sage does not.
Rosemary Salvia rosmarinus	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.	Needs light. Surface sow it, keep it warm, and be patient — two to three weeks is normal.
Chives Allium schoenoprasum	Germinates warm in one to two weeks. Use fresh seed — allium seed loses viability faster than most.
Lemon balm Melissa officinalis	Needs light, so surface sow. It spreads hard once established — a container is worth considering.
Borage Borago officinalis	Direct sow and cover — it wants darkness. Self-seeds enthusiastically forever after.
Blazing star Liatris spicata	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.
False indigo Baptisia australis	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.
Dianthus / sweet William Dianthus spp.	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.
Bellflower Campanula spp.	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.
Love-in-a-mist Nigella damascena	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.

Seeds that will die out there (13)

This is the part the seed lists skip. Every one of these is frost-tender and has no cold dormancy, so the winter offers it nothing and threatens it with everything. The real danger is not January — it is a mild week in March that brings them up, followed by one more hard night.

Start these indoors under lights, or direct sow them after your last frost. If you are not sure when that is, the seed starting calculator works backwards from your own frost date.

Frost-tender seeds that should not be winter sown
Plant	What to know
Zinnia Zinnia elegans	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.	Germinates in a few days at room temperature. Chilling it wastes a month and gains nothing.
Cosmos Cosmos bipinnatus	No dormancy. Rich soil gives you tall leafy plants and few flowers, so sow it somewhere poor.
Sunflower Helianthus annuus	Direct sow after frost. The real threat is birds and mice taking the seed, not dormancy.
Nasturtium Tropaeolum majus	Soak the large seed overnight instead. Poor soil gives more flowers and fewer leaves.
Morning glory Ipomoea spp.	A hard seed coat, not dormancy. Nick it with a file or soak it overnight and it comes up fast.
Petunia Petunia × atkinsiana	Dust-fine seed that needs light and warmth. Surface sow and do not let it dry out.
Celosia Celosia argentea	A heat lover. Sow into warm soil after frost; cold treatment only delays it.
Gomphrena (globe amaranth) Gomphrena globosa	Warm-season annual. Soaking the fluffy seed overnight helps more than any cold period would.
Strawflower Xerochrysum bracteatum	Needs light to germinate. Surface sow into warm compost after the last frost.
Dahlia (from seed) Dahlia spp.	Seed-grown dahlias germinate warm in about a week and will not come true to a named parent. Tubers do.
Tomato Solanum lycopersicum	Wants heat, around 21–27°C. Cold seed is the opposite of what it needs.
Basil Ocimum basilicum	One of the most cold-sensitive things in the garden at every stage. Sow warm, plant out late.

The milk jug, step by step

Rinse a translucent plastic milk jug and take the cap off. The cap stays off all winter — that opening is the vent.
Make four or five drainage holes in the base. A heated skewer goes through cleanly; a knife tends to split the plastic.
Cut around the jug about 10cm up, leaving a short section below the handle uncut so the top stays attached as a hinged lid.
Fill the base with 8–10cm of damp potting compost and firm it lightly. Less depth than this dries out too fast in spring.
Sow at the depth that species wants, which is not always covered — several of the seeds here need light and must sit on the surface.
Water it thoroughly and let it drain before closing.
Tape the cut shut all the way round with strong waterproof tape.
Label it twice: one waterproof label pushed into the compost, and the name written on the jug itself.
Stand it outdoors somewhere open, in full sun, where snow and rain reach it. Not against a warm house wall and not under cover.
Leave it alone until spring. When seedlings appear, open the lid on warm days and start checking whether it needs water.

Label it twice. A marker pen on the outside of a jug fades to nothing by March in full sun, and a jug of unidentified seedlings is a jug you will not plant with any confidence.

When to start

Any time from around the winter solstice up to about six weeks before your last frost. Seed does not germinate on a date, it germinates on conditions, so sowing in December rather than January mostly changes how long the jug stands there before anything happens.

The one thing that does matter is that the cold is real. A species wanting four weeks of cold, moist conditions needs somewhere that genuinely stays cold for four weeks. Where winters are mild enough that hard frost never settles in, winter sowing stops being stratification and becomes an early sowing in a plastic box — still useful for the hardy group above, no use at all for the first one. In that case a refrigerator gives you a cold period the weather will not.

Germination is also the point at which the jug stops being low-maintenance. Once seedlings are up, a sealed container in spring sun heats and dries out quickly — open it wider on warm days and check the compost far more often than you did all winter.

The tables print on their own, without the navigation. Choose “Save as PDF” in the print dialog to keep a copy.

Frequently asked questions

What is winter sowing?

Winter sowing is starting seed outdoors in midwinter inside a vented container — usually a translucent milk jug cut most of the way round — and leaving it out through the cold. The container behaves like a small unheated greenhouse: it holds moisture, lets light through, and still exposes the seed to freezing and thawing. For seed that needs a cold, moist period before it will germinate, that is cold stratification happening by itself, outdoors, for free.

When should I start winter sowing?

Any time from around the winter solstice until about six weeks before your last frost. The seed will not germinate until conditions are right, so sowing in late December rather than late January mostly changes how long the jug sits there. What matters far more is that the cold period is genuinely cold — in zones warm enough that hard frost never arrives, winter sowing stops doing anything a spring sowing would not do.

Which seeds are best for winter sowing?

The ones that need a cold, moist period to break dormancy, because the winter supplies it at no cost and with no refrigerator space. Milkweed, echinacea, columbine, bee balm, aster, delphinium and lavender are all in this group. Hardy annuals and biennials such as calendula, larkspur, bachelor's buttons and pansy are also worth a jug — not because they need the cold, but because they tolerate it and get you an earlier start.

Can you winter sow tomatoes?

No. Tomato is frost-tender and has no cold dormancy to break, so it gains nothing from the cold and will be killed by it if it germinates during a warm spell and then freezes. The same applies to basil, zinnia, marigold, cosmos and nasturtium. These want warm soil and belong indoors under lights, or direct sown after your last frost.

Is there a printable winter sowing seed list?

Yes — use the print button above the FAQ, or just print this page. The tables print on their own without the navigation, one row per plant, and choosing “Save as PDF” in the print dialog keeps a copy. We publish it this way rather than as a separate downloadable file so that the list you print is the current one; a PDF made once would quietly go out of date as species are added or corrected.

Can you winter sow in something other than milk jugs?

Yes. Anything translucent, roughly 10cm or deeper, with drainage holes in the base and vent holes in the top will work — clear takeaway containers, 2-litre bottles cut in half, salad boxes. The jug is popular because it is free, the handle makes it easy to move, and its shape holds enough depth of compost. Nothing about the method depends on it being a milk jug specifically.

Do I need to water winter sown containers?

Rarely, and that is most of the appeal. Snow and rain enter through the vent holes and the container keeps the moisture in. Check them if you get a long dry, mild spell, and check them properly once the weather warms in spring — that is when a jug can dry out fast and kill seedlings that have already germinated.

Does winter sowing replace cold stratification in the fridge?

For most species, yes — it is the same treatment delivered by the weather instead of the refrigerator, and it is why so many native perennials are easier winter sown than started indoors. The refrigerator is better when you need control: a precise number of weeks, a species that needs a long period you would rather start early, or a mild winter that cannot be relied on to stay cold.