We get a lot of questions about why your seedlings didn't sprout. All vegetables are different and sprout in different conditions. Some sprout in early spring in the cold, others in the middle of the summer when it's hot. For this reason, not everything will sprout in your home in a window sill. For some it is too warm, for others it is too cold. This chart will help you determine what temperature is optimal for various vegetables, and also how long you can expect it to take for your seeds to germinate at a given temperature. It isn't fool proof, however. They planted all their seeds at 1/2 inch deep, which is too deep for most vegetables. From personal experience, lettuce germinates best a little cooler than they state. But it is useful as a guide, especially for the times to germination at various temperatures.

Soil Temperature Conditions for Vegetable Seed Germination (in Degrees F)

Vegetable	Minimum	Optimum Range	Optimum	Maximum
Asparagus	50	60-85	75	95
Bean	60	60-85	80	95
Beet	40	50-85	85	95
Cabbage	40	45-95	85	100
Carrot	40	45-85	80	95
Cauliflower	40	45-85	80	100
Corn	50	60-95	95	105
Cucumber	60	60-95	95	105
Eggplant	60	75-90	85	95
Lettuce	35	40-80	75	95
Muskmelon	60	75-95	90	100
Onion	35	50-95	75	95
Parsley	35	50-85	75	90
Parsnip	35	50-70	65	85
Pea	40	40-75	75	85
Pepper	60	65-95	85	95
Radish	40	45-90	85	95
Spinach	35	45-75	70	85
Squash	60	70-95	95	100
Swiss Chard	40	50-85	85	95
Tomato	50	60-85	85	95
Turnip	40	60-105	85	105
Watermelon	60	70-95	95	105

Data Compiled by J.F. Harrington, Dept of Vegetable Crops, University of CA at Davis

Days to Appearance of Seedlings at Various Soil Temperatures (seeds planted at 1/2 inch depth, temperatures in degrees F)

Vegetable	32	41	50	59	68	77	86	95	104
Asparagus	x	x	53	24	15	10	11	19	28
Bean	x	x	x	16	11	8	6	6	x
Beet	...	42	17	10	6	5	4	4	...
Cabbage	...	...	15	9	6	4	3	...	...
Carrot	x	51	17	10	7	6	6	8	x
Cauliflower	...	...	19	10	6	5	4	...	...
Corn	x	x	22	12	7	4	4	3	x
Cucumber	x	x	x	13	6	4	3	3	...
Eggplant	...	...	...	13	8	5	...	...	...
Lettuce	49	15	7	4	3	2	2	x	x
Muskmelon	...	...	...	...	8	4	3	...	...
Onion	135	31	13	7	5	4	4	12	x
Parlsey	...	...	29	17	14	13	12	...	...
Parsnip	171	57	27	19	14	15	32	x	x
Pea	...	36	13	9	7	6	6	...	...
Pepper	x	x	x	25	12	8	8	9	x
Radish	...	29	11	6	4	3	3	...	...
Spinach	62	22	12	7	6	5	6	x	x
Tomato	x	x	43	14	8	6	6	9	x
Turnip	x	x	5	3	2	1	1	1	2
Watermelon	...	x	...	...	12	5	4	3	...

X little or no germination

... not tested

Data Compiled by J.F. Harrington, Dept of Vegetable Crops, University of CA at Davis