Flowers to Winter Sow

Group 1 – Seeds That Require Cold Stratification

Some seeds have built-in dormancy mechanisms. They need weeks to months of cold, moist conditions to break dormancy—so they can germinate reliably after winter and a steady spring warm-up. Start group 1 seeds as early as the start of when average daily lows drop below 40°F and stay there consistently. This timing will allow your seeds exposure to the cool-moist conditions they need to break dormancy.

Not confident on when your window for cold stratification starts?

Go to weatherspark.com
Type your city
Scroll to "Temperature," look for "Daily low temperatures"
Find the date when the dark blue band (average low) drops below 40 °F and stays there, that's the ideal time to start winter sowing Group 1 seeds for your garden. The window closes when it climbs back above 40 °F.

Tips:

Know the length of cold stratification needed for the seeds you are sowing so you don't miss the cold period.
Sow just before or after your cold stratification window begins.
Sow all your native and perennial seeds at the start of this window, and you won't miss the cold period.

North American Natives

This list includes a small sampling of some of the most popular North American native plants to winter sow, but don't stop here. Research specific plant varieties native to your region.

Anise Hyssop (Agastache foeniculum)
Bee Balm (Monarda spp.)
Black-Eyed Susan (Rudbeckia spp.)
Blazing Star (Liatris spicata)
Boneset (Eupatorium perfoliatum)
Butterfly Weed (Asclepias tuberosa)
Cardinal Flower (Lobelia cardinalis)
Columbine (Aquilegia canadensis)
Compass Plant (Silphium laciniatum)
Coreopsis (Coreopsis spp.)
Culver’s Root (Veronicastrum virginicum)
Cup Plant (Silphium perfoliatum)
Echinacea (Purple Coneflower)
Foxglove Beardtongue (Penstemon cobaea)
Goldenrod (Solidago spp.)
Helianthus (Helianthus spp.)
Ironweed (Vernonia noveboracensis)
Joe-Pye Weed (Eutrochium purpureum)
Lacy Phacelia (Phacelia tanacetifolia)
Liatris (Liatris spp.)
Lupine (Lupinus perennis)
Milkweed (Asclepias spp.)
Mountain Mint (Pycnanthemum spp.)
Aster (Symphyotrichum spp.)
New Jersey Tea (Ceanothus americanus)
Obedient Plant (Physostegia virginiana)
Phlox (Phlox spp.)
Rattlesnake Master (Eryngium yuccifolium)
Smooth Penstemon (Penstemon digitalis)
Spiderwort (Tradescantia spp.)
Virginia Bluebells (Mertensia virginica)
Wild Bergamot (Monarda fistulosa)
Wild Blue Indigo (Baptisia australis)
Wild Ginger (Asarum canadense)
Wild Strawberry (Fragaria vesca)
Yarrow (Achillea millefolium)

Perennials & Biennials

Agastache
Anise Hyssop
Artemesia
Asters
Astilbe
Balloon Flower
Baptisia
Bee Balm
Bellflower
Black-Eyed Susans
Blanket Flower
Bloodroot
Blue Beard
Blue Cap Sea Holly
Blue Fescue
Blue Mist Flower
Blue-Eyed Grass
Boneset
Butterfly Weed
Campanula
Campion
Canterbury Bells
Catmint
Chinese Lanterns
Chocolate Daisy
Clematis
Clover
Columbine
Compass Plant
Coneflowers
Coral Bells
Coreopsis
Cranesbill
Creeping Thyme
Culver's Root
Cup Plant
Cupid's Dart
Delphinium
Dianthus
Echinacea
English Daisy
Evening Primrose
False Indigo
False Nettle
Feverfew
Flax
Fleabane
Foamflower
Fountain Grass
Foxglove
Foxglove Beardstongue
Gaillardia
Gaura
Geranium
Geum
Globe Thistle
Goat's Beard
Golden Alexanders
Goldenrod
Hardy Hibiscus
Heather
Helenium
Helianthus
Hollyhock
Hosta
Iceplant
Ironweed
Jack-in-the-Pulpit
Jacob's Ladder
Joe-Pye Weed
Lamb's Ears
Lavender
Leadplant
Leadwort
Liatris
Lobelia
Lupine
Lynchis
Maltese Cross
Malva
Meadowsweet
Milkweed
Money Plant
Mountain Bluet
Mountain Mint
New Jersey Tea
Nodding Onion
Obediant Plant
Ox-Eye Daisy
Painted Daisy
Pampas Grass
Pasque Flower
Pearly Everlasting
Penstemon
Perennial Flax
Persian Buttercup
Phlox
Primrose
Pussytoes
Pyrethrum
Rattlesnake Master
Rockcress
Rose Campion
Rosinweed
Rudbeckia
Russian Sage
Rye
Santolina
Sea Holly
Sea Pink
Sedges
Sedum
Senna
Shasta Daisy
Siberian Wallflowers
Spiderwort
Tickseed
Turtlehead
Verbascum
Verbena
Vervain
Virginia Blue Bells
Virginia Snakeroot
Wild Bergamot
Wild Geranium
Wild Ginger
Wild Strawberry
Wingstem
Wooly Dutchman's Pipevine

Group 2 – Seeds That Germinate in Cool Temperatures

Group 2 seeds germinate in cool weather and thrive when given the chance to grow in cool temperatures. To know when to sow these seeds in your climate, you need to understand what type of winter you have: mild or harsh?

Mild Winter

Rarely dips below 28°F for extended periods. (Rule of thumb: If your ground freezes are light, short, or rare, you're in a mild winter area.)

When to start: Begin Group 2 seeds as early as the first frost in fall and throughout the winter months while nights stay below 40°F. Seedlings will germinate once exposed to cool temperatures and can overwinter safely with minimal protection due to their hardiness. Keep jugs in the shade until germination, and monitor soil moisture regularly. The warmer your winter, the earlier you'll want to start.

Harsh Winter

Regularly drops below 28°F and experiences several days, weeks, or even months of hard freeze. (Rule of thumb: If your ground freezes deeply and stays frozen for more than a few days, you're in a harsh winter area.)

When to Start: Begin Group 2 seeds in mid-winter to avoid premature sprouting during late warm spells that come before deep freezes. Start no later than 8 weeks before your average last frost date to ensure high germination rates and optimal growth before summer heat arrives.