Winter Sowing: A Beginner’s Guide To Growing Cold-Hardy Seeds Outdoors (Even In Freezing Temperatures)

Winter Sowing is a cost-effective, low-maintenance way to grow many types of seeds into healthy baby plants. A repurposed milk jug or other plastic recyclable container can easily be made into a mini greenhouse to help seedlings germinate in early spring.

Winter Sowing is a temperate-climate outdoor seed starting method which uses repurposed plastic containers to create mini outdoor greenhouses. Recyclables such as milk jugs are adapted to have a removable top, along with air holes and drainage slits. This prepared “flat” is then filled with moist potting soil, into which seeds are sown. The container is then taped shut and placed outdoors to be exposed to the elements (including freezing temperatures, snow, and rain).

Read on to learn all about the benefits of Winter Sowing your garden seeds, as well as exactly how to do Winter Sowing at home in repurposed milk jugs or other recyclable containers.

winter sowing - milk jugs outside on table in the snow

Introduction To Winter Sowing

Winter Sowing is a seed-starting method invented by gardener Trudi Greissle Davidoff of New York. She had lots of seeds but had very limited indoor space in which to start them using traditional indoor seed starting methods. She shared her winter sowing method in the essay How to Winter Sow Seeds Outdoors (August 17th, 2000), and the method has taken off as an easy, low-maintenance way to grow hardy seedling plants at home.

“Winter Sowing: A propagation method used throughout the winter where temperate climate seeds are sown into protective vented containers and placed outdoors to foster a naturally timed, high percentage germination of climate tolerant seedlings.”

Winter Sowing Method, USDA NAL Agricultural Thesaurus and Glossary

The seed starting method of Winter Sowing is one of the easiest and most cost-effective ways to grow seeds into healthy baby seedling plants in a protected environment. The seedlings generally don’t need much care once they’ve germinated, and also don’t require the standard “hardening off” that indoor-raised seedlings require to become acclimated to the weather outdoors. Winter Sowing is the perfect method to try if love lots of plants (for not much time or money).

Winter Sowing Tutorial – Basic Steps

Here are the basic steps to the Winter Sowing gardening method of starting seeds:

  • Collect recyclable containers to make flats (milk jugs, take out trays)
  • Make a hinge in containers without a top (like milk jugs, pop bottles)
  • Cut drainage holes in the bottom of each flat
  • Cut air circulation holes in the top of each flat (or take off cap)
  • Label each flat with a UV-resistant garden permanent marker
  • Dampen potting soil with clean water (clumpy, not muddy)
  • Fill each flat with potting soil, about 3″-4″ deep
  • Plant one type of seeds in each container/flat.
    • Tiny seeds are sprinkled onto the surface and patted down
    • Larger seeds are pushed down into the soil to specified depth
  • Tape the top of the flat down to the bottom with duct tape or packing tape
  • Place the planted flat outdoors, exposed to precipitation and sun
  • Watch for seeds to germinate in the spring into tiny sprouts
  • Cut more holes/side windows for increased air circulation as temperatures increase
  • Open the top on warm days and consider removing it after chance of frost
  • Gently remove the seedlings from the container and break or cut apart
  • Transplant the seedlings into the garden
Supplies for Winter Sowing
Milk jug ready for winter sowing
Pea seeds laid out on potting soil for winter sowing
winter sown milk jugs on table in the snow

Benefits & Drawbacks of The Winter Sowing Seed Starting Method

Here are some of the benefits and drawbacks of Winter Sowing:

Benefits of Winter Sowing

  • Low Cost – no special seed starting flats, lights, or heating mats needed
  • Low Difficulty – steps are simple and can be done by beginners
  • Low Maintenance – little care or upkeep required after planting
  • No Indoor Space – doesn’t occupy interior living space
  • Energy Efficient – no electric plant lights or heating mats required
  • Lots of Seedlings – typically very high germination rates
  • Seedling Health – seedings are naturally stocky and hardy
  • No Hardening Off – no transition back-and-forth period
  • Keeps Seeds in Place – keeps directly-planted seeds from washing away
  • Protects From Birds – protects directly-planted seeds from being eaten
  • January Gardening – allows you to reasonably start gardening very early

Drawbacks To Winter Sowing

  • Timing – seeds germinate when they want to (can be months after planting)
  • Late Cold Spell – late spring cold spells can kill tender seedlings that germinated during warmer temperatures (they may survive with extra cover during the cold temperatures)
  • Cover Chores – covers must be removed on warm days and replaced on cool nights, and more air vents will likely be required
  • Lid Removal – cover lids often must be cut off completely as seedlings outgrow available height
  • Transplanting – requires pulling seedling mass out of container and transplanting seedlings into the ground (unlike direct seeding)
Winter sowing flower seeds - west coast seeds
Cold-Hardy Greens For Winter Sowing in February

The Best Types Of Seeds For Winter Sowing

The best types of seeds for winter sowing are frost-tolerant seeds, especially those that self-sow and can be direct-sown early. This includes many native perennials and wildflowers, as well as select herb and veggie seeds.

Flower Seeds For Winter Sowing

Here are some excellent flower seeds for winter sowing.

  • Aster (Aster)
  • Bachelor’s Button/Cornflower (Centaurea cyanus)
  • Balloon Flower (Platycodon grandiflorus)
  • Bee Balm (Monarda)
  • Bellflower (Campanula)
  • Black-Eyed Susan (Rudbeckia hirta)
  • Blanket Flower (Gaillardia)
  • Blue Wild Indigo (Baptisia australis)
  • Canterbury Bells (Campanula medium)
  • Cardinal Creeper (Ipomoea x multifida)
  • Cardinal Flower (Lobelia cardinalis)
  • Catnip (Nepeta)
  • Celosia (Celosia)
  • Columbine (Aquilegia)
  • Coneflower (Echinacea)
  • Cornflower (Centaurea cyanus)
  • Cosmos (Cosmos)
  • Cranesbill (Geranium)
  • Cypress Vine (Ipomoea quamoclit)
  • Daisy (Bellis perennis)
  • Delphinium (Delphinium)
  • Evening Primrose (Oenothera)
  • Foxglove (Digitalis)
  • Golden Everlasting/Strawflower (Xerochrysum bracteatum)
  • Hollyhock (Alcea)
  • Larkspur (Delphinium consolida)
  • Lavender (Lavandula)
  • Lupin (Lupinus)
  • Lyreleaf Greeneyes/Chocolate Flower (Berlandiera lyrata)
  • Marguerite (Argyranthemum frutescens)
  • Marigold (Calendula)
  • Monkshood (Aconitum)
  • Ornamental Tobacco (Nicotiana)
  • Pink (Dianthus)
  • Poppy (Papaver)
  • Snapdragon (Antirrhinum)
  • Sunflower (Helianthus)
  • Yarrow (Achillea millefolium)

Herbs

Here are some herbs that are great for Winter Sowing:

  • Chervil (Anthriscus cerefolium)
  • Chives (Allium schoenoprasum)
  • Cilantro (Coriandrum sativum)
  • Dill (Anethum graveolens)
  • Mint (Mentha)
  • Oregano (Origanum vulgare)
  • Parsley (Petroselinum crispum)
  • Sage (Salvia officinalis)
  • Salad Burnet (Sanguisorba minor)
  • Savory (Satureja hortensis)
  • Thyme (Thymus vulgaris)

Vegetable

Here are some cool-season vegetable seeds for Winter Sowing:

  • Arugula
  • Beets
  • Bok Choi
  • Broccoli
  • Brussel Sprouts
  • Cabbage
  • Carrots
  • Cauliflower
  • Collard Greens
  • Endive
  • Green Onion/Scallion
  • Kale
  • Kohlrabi
  • Leek
  • Lettuce
  • Onion
  • Pak Choi
  • Pea
  • Radicchio
  • Radish
  • Shallot
  • Spinach
  • Swiss Chard

There are countless more seeds that will work well for winter sowing! Even seeds that naturally live in warm climates can be winter sown (they just may need to be sown later in the winter and protected from any cool temperatures after germination).

When To Do Winter Sowing

Winter Sowing is done between the Winter Solstice and the last frost of Springtime. Most often, seeds are winter sown during the months of January-March in temperate climates. It’s not uncommon for gardeners to order their seeds on Boxing Day so they have them in hand for planting early in the New Year.

Most gardeners tend to spread their winter sowing planting out over several weeks or months. Seeds for plants that are hardy to your growing zone can be sown first – any time after winter solstice.

The seedlings of tender annuals grown in cold areas will need protection beyond what the milk jug or container lids provide. To mitigate losses of tender winter-sown plants, many gardeners wait until March or April to winter sow, or simply provide additional cover/warmth to the milk jugs during spring cold spells.

Using Milk Jugs to make seed starting flats
Cutting a milk jug for winter sowing container
Cutting drainage slits in bottom of milk jug
Labelling Milk Jugs with UV resistant markers for outdoors
Adding 3 or 4 inches deep of seed starting potting mix to milk jug
Planting snap peas in winter sowing jug
Pushing down seeds into potting mix
Taping up the milk jug to put it outdoors
planted winter sowing jug
garden markers and uv resistant paint pens

Mary Jane Duford

Mary Jane is a home gardener who loves creating healthy, welcoming spaces (indoors and out!) - About Mary Jane (https://www.homefortheharvest.com/authors/about-mary-jane-duford/)

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