"For every species of seed,there is an optimal soil temperature for germination,
and at that temperature,
the maximum number of seeds will germinate
and in less time than at any other temperature."
Tom Clothier's Garden Walk and Talk
As I contemplate the early sowing of seeds for Spring planting I have noted the optimal soil temperature for germination and growth. It becomes clear why summer crops need added heat to germinate and grow early in the season.
Optimal soil temperatures for seed germination and preferred growing range:
Amaranth Amaranthus gangeticus 28C; range 16C-30C
Artichoke Globe Cynara scolymus 20C; range 15C-18C
Asparagus Asparagus officinalis 25C; range 16C-30C
Basil Ocimum basilicum 30C; range 18C-35C
Bean Runner Phaseolus coccineus 25C; range 16C-30C
Beans Broad Vicia faba 17C; range 6C-24C
Beans Bush Phaseolus nanus 25C; range 16C-30C
Beetroot Beta vulgaris 25C; range 8C-30C
Broccoli Brassica oleracea var. italica 20C; range 7C-30C
Cabbage Brassica oleracea var. capitata 25C; range 10C -35C
Capsicum Capsicum annuum 20C; range 18C-35C
Carrots Daucas carota 25C; range 10C-30C
Cauliflower Brassica oleracea 25C; range 10C-30C
Celery Apium graveolens var. dulce 20C; range 12C-21C
Chillies Capsicum annuum 20C; range 18C-35C
Clover Red Trifolium pratense 25C; range 20C-25C#
Corn Sweet Zea mays 25C; range 16C-35C
Cossack Pineapple Physalis pruinosa 27C; range 10C-24C ****
Cucumber Cucumis sativus 35C; range 16C-35C
Eggplant Solanum melongena 30C; range 24C-32C
Kale Brassica oleracea var acephala 20C; range 8C-30C
Kohl Rabi Brassica oleracea var. gongylodes 15C; range 8C-30C
Leeks Allium ampeloprasum var. porrum 20C; range 8C-30C
Lettuce Lactuca sativa 23C; range range 8C-27C
Luffa Luffa aegyptica 35C; range 20C-30C
Melon Cucumis melo 32C; range 20C-32C
Onion Allium cepa 23C; range 8C-30C
Parsnip Pastinaca sativa 17C; range 6C-21C
Peas Pisum sativum 23C; range 8C-23C
Pumpkin Cucurbita species 35C; range range 20C-35C
Radish Raphanus sativus 30C; range range 8C-30C
Silverbeet Beta vulgaris 25C; rangerange 10C-30C
Spinach English Spinacia oleracea 21C; range 10C-25C
Sunflower Helianthus annuus 30C; range 15C-30C
Tomato Lycopersicon esculentum 30C; range 16C-35C
Watermelon Citrullus lanatus 35C; range 21C-35C
Zucchini/Squash Cucurbita pepo 35C; range 21C-35C
This is not a complete listing.
It contains many of the seeds I grow, more information is available on the links below.
Further reading/sources:
Information has been sourced from the Phoenix Seed catalogue and Eden Seeds Growing Chart variations may occur.
Locally sourced seed will have adapted to local climatic conditions and would have a wider variation of tolerated temperatures.
****information for Cossack Pineapple from This Site
# and for the Clovers Here
Information also available on individual plant listings on the Gardenate site
The article When to Plant on this link contains a chart with more “realistic” soil temperatures for germination. (In Fahrenheit)
