Optimum germination and growing temps for veg

Blue = cold temps for growing
Green = optimum temp for germination indoors or growing outdoors
Red = optimum for outdoor germination and growing

Practically speaking - for optimum growth:


Jan to End of Feb = Sow all plants indoors with heat / Some harvesting of last year's crops
Mar to End of May = Sow hardy plants indoors without heat / Harden off hardy plants outdoors with protection
Jun to End of July = Sow tender plants indoors without heat / Plant out hardy plants without protection / Early harvesting
Aug to End of Sept = All plants mature outdoors / Start major harvesting

Oct to Dec = Last bit of harvesting


Useful links:

• http://www.ehow.com/facts_7299310_optimum-growing-temperatures-growing-vegetables.html
• http://www.ehow.com/facts_7611079_coldest-vegetable-plants-can-handle.html

Selected quotes from above links:


Germination

Proper temperatures for germination range from as low as 60 degrees F [15°C] for cabbage and head lettuce up to as high as 90 or 95 degrees F [32°C] for eggplant, squash and melons. Several vegetables germinate best at a more moderate 70 to 80 degrees F [26°C], including cruciferous vegetables such as broccoli and cabbage, along with tomatoes and peppers.

Cool-Season Vegetables

Hardy cool-season vegetables -- such as onions, lettuce and peas -- grow in daytime temperatures as low as 40 degrees F [5°C], according to Colorado State University. Slightly less hardy cool-season crops -- including beets, carrots and potatoes -- grow in similar temperatures but do not tolerate freezing nighttime temperatures that typically accompany such low daytime temperatures.

Warm-Season Vegetables
Warm-season vegetables survive and grow well only when temperatures remain above at least 60 degrees F during the day. Higher temperatures between 70 and 95 degrees F [32°C] ensure optimum growth of these vegetables. The tenderest of the warm-season vegetables -- such as cantaloupe, tomato, watermelon and pepper -- show stunted growth if temperatures fall below 55 degree F [15°C] at any time during the day and may experience negative effects from even cool spring breezes.


As an interesting observation - my greenhouse got up to 30 °C today, even though outside it was 14 °C. However, overnight it got as low as 6°C. So it goes to show that most seedlings will germinate in a greenhouse but without heat the most tender, like tomatoes and squashes, will probably suffer.