Optimal Soil Temperature For Flower Seed Germination

Seeds are in a dormant state until the right conditions occur which triggers the end of dormancy. There are a number of critical factors that determine when a seed will germinate including moisture, oxygen and the right soil temperature. Some seeds also require a period of cold, known as cold stratification. This mimics the normal winter a seed would usually experience before germinating once temperatures warm up in spring.

We recommend gardeners purchase a soil temperature thermometer to check soil temperature before sowing seeds. These are available from most nurseries or online.

Celsius

Fahrenheit

Stratification?

African daisy (Arctotis stoechadifolia) 18 – 21 65 – 70 No
African daisy (Osteospermum spp.) 21 – 24 70 – 75 No
Alyssum (Lobularia maritima) 12 – 23 55 – 75 No
Amethist flower (Browallia spp.) 18 – 21 65 – 70 No
Aster (Aster spp.) 18 – 23 65 – 75 No
Baby’s breath (Gypsophila spp.) 15 – 18 60 – 65 No
Balloon flower (Platycodon grandiflorus) 16 – 20 60 – 68 No
Bear’s breeches (Acanthus mollis) 18 – 21 65 – 70 No
Bee balm (Monarda didyma) 16 – 21 60 – 70 No
Begonia (Begonia spp.) 18 – 21 65 – 70 No
Bellflower (Campanula spp.) 21 – 23 70 – 75 Yes
Bells-of-Ireland (Moluccella laevis) 13 – 18 55 – 64 Yes
Black-eyed Susan (Rudbeckia hirta) 18 – 21 65 – 70 Yes
Bleeding heart (Dicentra spectabilis) 4 – 12 40 – 55 Yes
Boltonia (Boltonia spp.) 18 – 21 65 – 70 No
Borage (Borago officinalis) 18 – 29 65 – 85 No
Bugle flower (Ajuga spp.) 10 – 15 50 – 60 No
Bugloss (Anchusa capensis) 18 – 21 65 – 70 No
Butter daisy (Melampodium
paludosum
)
18 – 21 65 – 70 No
Butterfly flower (Schizanthus spp.) 18 – 22 65 – 71 No
Butterfly weed (Asclepias tuberosa) 18 – 24 65 – 75 Yes
Calendula (Calendula officinalis) 18 – 21 65 – 70 No
Californian poppy (Eschscholzia californica) 12 – 21 55 – 70 No
Candytuft (Iberis spp.) 23 – 29 75 – 85 No
Canterbury bells (Campanula medium) 18 – 21 65 – 70 Yes
Cape jewels (Nemesia strumosa) 13 – 18 55 – 65 No
Carnation (Dianthus spp.) 15 – 21 60 – 70 No
Catnip/catmint (Nepeta spp.) 18 – 21 65 – 70 No
Chamomile (Matricaria chamomilla) 18 – 21 65 – 70 Yes
Chilean bellflower (Nolana paradoxa) 20 – 22 68 – 72 No
Chinese aster (Callistephus chinensis) 20 – 23 68 – 73 No
Chinese forget-me-not (Cynoglossum amabile) 18 – 20 65 – 68 No
Chinese lantern (Physalis alkekengi) 16 – 21 60 – 70 No
Chrysanthemum (Chrysanthemum spp.) 18 – 23 65 – 75 No
Clematis (Clematis spp.) 20 – 22 68 – 73 Yes
Cliquefoil (Potentilla spp.) 19-21 67-70 No
Cohosh (Cimicifuga spp.) 18 – 21 65 – 70 No
Columbine (Aquilegia spp.) 10 – 12 50 – 55 Yes
Common rockrose (Helianthemum nummularium) 21 – 24 70 – 75 No
Common sneezeweed (Helenium autumnale) 19 – 22 65 – 73 No
Coral bell (Heuchera spp.) 18 – 21 65 – 70 No
Corncockle (Agrostemma githago) 15 – 21 60 – 70 No
Cornflower (Centaurea cyanus) 15 – 21 60 – 70 No
Cosmos (Cosmos bipinnatus) 21 – 25 70 – 77 No
Cup and saucer vine (Cobaea scandens) 21 – 23 70 – 75 No
Cupflower (Nierembergia spp.) 21 – 23 70 – 75 No
Cupid’s bow (Achimenes spp.) 21 – 23 70 – 75 No
Cupid’s dart (Catananche caerulea) 20 – 23 68 – 75 No
Cyclamen (Cyclamen spp.) 18 – 20 65 – 68 No
Dahlberg daisy (Dyssodia tenuiloba) 18 – 21 65 – 70 No
Dahlia (Dahlia spp.) 21 – 23 70 – 75 No
Delphinium (Delphinium elatum) 15 – 20 59 – 68 Yes
Echinacea (Echinacea spp.) 18 – 21 65 – 70 Yes
Edeiweiss (Leontopodium alpinum) 18 – 21 65 – 70 Yes
English daisy (Bellis perennis) 18 – 21 65 – 70 No
Evening primrose (Oenothera spp.) 21 – 26 70 – 80 No
Everlasting (Helichrysum bracteatum) 21 – 24 70 – 75 No
False sunflower (Heliopsis spp.) 21 – 23 70 – 73 No
Fan flower (Scaevola aemula) 20 – 22 68 – 71 No
Firecracker flower (Crossandra infundibuliformis) 21 – 27 70 – 80 No
Flax (Linum usitatissimum) 18 – 21 65 – 70 No
Fleabane (Erigeron spp.) 18 – 21 65 – 70 No
Floss flower (Ageratum houstonianum) 24 – 29 75 – 85 No
Forget-me-not (Myosotis spp.) 18 – 21 65 – 70 No
Foxglove (Digitalis spp.) 15 – 18 60 – 65 No
Garden heliotrope (Heliotropium spp.) 18 – 21 65 – 70 No
Gay feather (Liatris spp.) 18 – 21 65 – 70 Yes
Gazania (Gazania spp.) 15 – 18 60 – 65 No
Gerbera (Gerbera spp.) 21 – 23 70 – 73 No
Geum (Geum spp.) 18 – 21 65 – 70 No
Globeflower (Trollius spp.) 18 – 21 65 – 70 Yes
Glory of the snow (Chionodoxa spp.) 10 – 15 50 – 59 Yes
Gloxinia (Sinningia speciosa) 19 – 21 66 – 70 No
Goldencup (Hunnemannia fumariifolia) 19 – 21 66 – 70 No
Goldenrod (Solidago spp.) 20 – 22 68 – 71 Yes
Goldentuft (Aurinia saxatilis) 15 – 21 59 – 70 No
Hellebore (Helleborus spp.) 18 – 21 65 – 70 Yes
Hibiscus (Hibiscus spp.) 21 – 26 70 – 75 No
Hollyhock (Alcea rosea) 15 – 21 60 – 70 Yes
Iceland poppy (Papaver nudicaule) 18 – 24 65 – 75 Yes
Impatiens (Impatiens spp.) 21 – 23 70 – 73 No
Jacob’s ladder (Polemonium spp.) 18 – 21 65 – 70 No
Laceflower (Trachymene coerulea) 18 – 21 65 – 70 No
Ladys purse (Calceolaria spp.) 21 – 23 70 – 73 No
Larkspur (Consolida ambigua) 10 – 12 50 – 55 Yes
Lavender (Lavandula spp.) 18 – 21 65 – 70 No
Leopard plant (Ligularia spp.) 18 – 21 65 – 70 No
Linaria (Linaria spp.) 12 – 18 55 – 65 Yes
Lisianthus (Eustoma grandiflorum) 22 – 23 72 – 73 No
Livingstone daisy (Dorotheanthus
bellidiformis
)
18 – 24 65 – 78 No
Lobelia (Lobelia spp.) 18 – 23 65 – 73 No
Love-lies-bleeding (Amaranthus caudatus) 20 – 28 68 – 82 No
Lupine (Lupinus spp.) 12 – 21 55 – 70 Yes
Madagascar periwinkle (Catharanthus
roseus
)
24 – 27 75 – 80 No
Marigold (Tagetes spp.) 21 – 23 70 – 73 No
Marshmallow plant (Althaea officinalis) 15 – 21 60 – 70 Yes
Mexican creeping zinnia (Sanvitali procumbens) 18 – 21 65 – 70 No
Mignonette (Reseda odorata) 12 – 14 53 – 57 No
Monkey flowers (Mimulus spp.) 15 – 21 60 – 70 No
Monk’s hood (Aconitum spp.) 12 – 15 55 – 60 Yes
Morning glory (Convolvulus spp.)
20 – 21 68 – 70 No
Nasturtium (Tropaeolum majus) 15 – 18 60 – 65 No
Nemesia (Nemesia spp.) 12 – 18 55 – 65 No
Nemophila (Nemophila spp.) 12 – 15 55 – 60 No
Nigella (Nigella damascena) 15 – 18 60 – 65 No
Obedient plant (Physostegia virginiana) 18 – 21 65 – 70 No
Pansy (Viola tricolor var. hortensis) 15 – 23 60 – 73 No
Pearly everlasting (Anaphalis margaritacea) 18 – 21 65 – 70 No
Persian violet (Exacum affine) 21 – 24 70 – 78 No
Petunia (Petunia spp.) 18 – 23 65 – 73 No
Phlox (Phlox spp.) 15 – 18 60 – 65 No
Poppy (Papaver spp.) 15 – 20 60 – 68 Yes
Portulaca (Portulaca spp.) 21 – 26 70 – 80 No
Pride of Madeira (Echium candicans) 15 – 20 60 – 68 No
Primrose (Primula spp.) 15 – 18 60 – 65 Yes
Purple rock cress (Aubrieta deltoidea) 18 – 21 65 – 70 No
Queen Anne’s lace (Daucus carota) 16 – 18 60 – 65 No
Rock cress (Arabis spp.) 18 – 21 65 – 70 No
Salvia (Salvia officinalis) 21 – 23 70 – 73 No
Satin flower (Clarkia amoena) 21 – 23 70 – 73 No
Shooting star (Dodecatheon meadia) 18 – 21 65 – 70 Yes
Sea holly (Eryngium spp.) 18 – 23 65 – 73 Yes
Shasta daisy (Leucanthemum x superbum) 18 – 21 65 – 70 No
Snapdragon (Antirrhinum majus) 18 – 23 65 – 73 Yes
Snow-in-summer (Cerastium tomentosum) 18 – 21 65 – 70 No
Speedwell (Veronica spp.) 18 – 24 65 – 75 No
Spider flower (Cleome spinosa) 21 – 23 70 – 73 Yes
Statice (Limonium sinuatum) 15 – 20 60 – 68 No
Stock (Matthiola incana) 15 – 18 60 – 65 No
Stoke’s aster (Stokesia laevis) 21 – 24 70 – 75 No
Sunflower (Helianthus spp.) 21 – 23 70 – 73 No
Swan river daisy (Brachyscome iberidifolia) 21 – 24 70 – 78 No
Sweet pea (Lathyrus odoratus) 12 – 18 55 – 65 No
Trumpet flower (Incarvillea spp.) 18 – 21 65 – 70 No
Tweedia (Oxypetalum coeruleum) 18 – 21 65 – 70 No
Twinspur (Diascia spp.) 15 – 18 60 – 65 No
Verbena (Verbena spp.) 18 – 23 65 – 73 No
Viola (Viola spp.) 18 – 23 65 – 73 No
Virginian stock (Malcolmia maritima) 18 – 23 65 – 73 No
Wallflower (Erysimum cheiri, syn. Cheiranthus cheiri) 15 – 18 60 – 65 No
Wild indigo (Baptisia spp.) 18 – 21 65 – 70 No
Wishbone flower (Torenia fournieri) 21 – 23 70 – 75 No
Xeranthemum (Xeranthemum annuum) 24-35 75 – 95 No
Yarrow (Achillea spp.) 18 – 21 65 – 70 Yes
Yellow lotus (Nelumbo lutea) 21 – 24 70 – 78 No
Zinnia (Zinnia spp.) 21 – 23 70 – 73 No

Optimal soil temperature for flower germination PDF