Cool season crops generally perform best when highs are in the upper 60s and very low 70s and lows are in the low 50s. They tolerate temperatures below this range much better than those above this range.

Tomatoes and cukes do best at around 80/60 high/low.

Peppers, eggplant, melons etc at around 85/70

Okra at 90/75.

I think soil temperature matters more than air temps in the beginning of the growing season (both indoors and in the garden). I've found that heat loving plants like okra and egg plant grow better in containers than in the ground in my area. And peppers in containers often mature a week or more before the ones in the ground.

I believe that we are experiencing some effects of climate change, but I wouldn't throw out the temperature charts gardeners have been using for decades. I adjusted my zone from 5b to 6a a couple years ago because I am on the cusp of both and my conditions are changing. But only sometimes and by small amounts. We experienced record breaking cold temps and close to record breaking snow this winter. I don't want to start a debate, I just want to suggest that there is still a lot of wisdom to be had from all the gardening advice given in the past.

I'll put it this way. If you've got the right soil temperatures that a crop needs, chances are you've got the right air temperatures as well. This is for an unmulched garden and assuming that the temps stay fairly consistent over a period of a week.

Unless you're able to manipulate the temperature of the air and keep it consistent at all times there is really no reason to aim for an "ideal" anything. It's just not possible. Especially outside. Even day and night temperatures can fluctuate 20 or more degrees. So what's "ideal" during the day won't be "ideal" at night. You can influence air temps to an extent by growing under cover when it's chilly and by using shade cloth when it's warm (somewhat) but for the most part you're at the mercy of Mother Nature. As long as a crop is withing the range of low temp and high temp they will grow just fine.

Rodney

I am having trouble sorting out from your post the WHY you feel you need this information?

For the most part it doesn't exist so you won't find it. But why do you think you need it?

And the reason it doesn't exist is a) because in most ways it is irrelevant and experienced gardeners understand that, and b) it is useless to know even if it was available because it is beyond your control when gardening outside.

After all the air temp isn't a consistent thing so it isn't as if you are going to only plant on the day when the temp is X degrees but go out and pull up the plants 10 days later when the air temp rises or falls out of some artificial range of supposedly acceptable temps. Nor will you be lighting smudge pots, turning on fans or heaters. Best you can do is cover plants when the temp falls too low.

SlimeyO gave you the commonly accepted ranges for most crops above. Broccoli - 50-70 is as close to an air temp range you'll find.

It is soil temp that is vital to growing plants and to a large degree we can control that.

Now if growing in a greenhouse, yes that info is available because gh growers can control the air temps inside the structure.

Dave

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This post was edited by QuinnaBrennan on Fri, Apr 4, 14 at 23:25

From digdirt.... "Now if growing in a greenhouse, yes that info is available because gh growers can control the air temps inside the structure."........... Yea I was thinking about ways to have an ideal air temp when growing indoors and in a greenhouse from sprout to transplanting time to see if they grow healthier and better before transplant time....I currently have lists of a general idea of the height in the greenhouse to put the plants ....low to the ground for cold and higher up for hot. Thank you for the response digdirt and now thanks to you I am looking up soil temp control :). To Slimy_Okra...thanks for the temps!

Thanks theforgottenone for this message...
"Unless you're able to manipulate the temperature of the air and keep it consistent at all times there is really no reason to aim for an "ideal" anything. It's just not possible. Especially outside. Even day and night temperatures can fluctuate 20 or more degrees. So what's "ideal" during the day won't be "ideal" at night. You can influence air temps to an extent by growing under cover when it's chilly and by using shade cloth when it's warm (somewhat) but for the most part you're at the mercy of Mother Nature. As long as a crop is withing the range of low temp and high temp they will grow just fine."...
I sort of have a response to this....My greenhouse has about 7 to 8 different heights and I am trying to order my plants by temperature. .I was thinking about your response and I think the reason why I am looking for an ideal temp is because I am thinking about having the veggies at the correct height in order to have an ideal temp when the sun is out in the day. I was thinking this would maximize growing. Also for the nighttime thing I have a clear water aquirium and a ton of clear used milk bottles and soda bottles on the upper part of the green house where it gets above 100F...then at night when the heat stored in the water dissipates I have a minifan that blows the dissipated air down a vent into bricks on the floor of the greenhouse which keeps the temperatures much higher at the night. I am going to try a ton of science experiments...just don't know what they are yet :)

I guess right now if nothing else then I would like a confirmation that the order am putting the veggies in from to coldest to hottest loving plants is accurate (or close to accurate)

Here is the order again(and also on my flag cold-to-hot measurement picture)....
Coldest ….
1. Kale(pretty sure kale is one of the coldest if not the coldest)....I have this as a starting point in the center of the blue cross in the hot red Norwegian flag.......then it goes to the all blue, cold Greek flag starting with Spinach
2. Spinach(yellow and orange “Green Hornet” symbol...yellow and orange due to spinach goes well with high acidity tropical fruits in green smoothies...Green Hornet symbol is a double K...meaning high vitamin K content....which leafy greens have)
3. Leeks....I know that Leeks are very cold hardy but I am not sure if I should put leeks at the number 3 cold since leeks seem to have a large temperature range and the ideal soil and air temp may put leeks higher on this list....maybe somewhere from 4 to 6...idk(green and blue heart symbol.....heart for the allium family...as garlic is heart and soul of culinary science....I don't know if I got this right but for some reason I associated leeks with high water content and that's why I have the green and blue....do growing leeks like a lot of water?)
4. Turnip....Another large temperature range yet cold hardy veggie so I am not sure if number 4 would be the best place for Turnips( V for brassica family...V shape cause Kale is a brassica and has rigid V like edges(except for dinosaur kale).....symbol is red and white because Turnips are white and purplish-red)
5. Radish....From what I have researched I think radish has the largest temperature range yet..(Half of a triangle for taproots....red symbol due to the color of the radish....)
6. Head Lettuce(I have buttercrunch)...from what I have research this veggie seems to be the logical next one in order (single K for less vitemin K content but still a leafy green....yellow and green color....yellow for the color of butter)
7. Swiss Chard....next one in line I think?....(Double “green arrow” K...red and white..the color of the swiss flag)
8. Arugula....I really don't know about arugula haven't found much temp info on arugula....(single K for less vit K....black and green....black for pepper since arugula has a peppery flavor to it)
9. Romaine Lettuce....number 9 maybe? ….(single K for less vit K....red and yellow...the color of the Roman flag)
10. Parsley....or Peas or Broccoli or Brussel Sprouts idk...haven't done much herb temperature research yet...(H for low temp herbs....orange and green color...orange because I use parsley on my orange salmon recipe)
11. Cilantro...or Peas or Broccoli or Brussel Sprouts idk..haven't done much herb temperature research yet...(H for low temp herbs...white and red...the color of salsa! Which cilantro is good in)
12. Broccoli...or Brussel Sprouts or Peas?...(V for Brassicas....yellow and green symbol..reason: When brocolli flowers, it's yellow)
13. Brussel Sprouts? (V for Brassicas....yellow and blue symbol..reason: the flag color of Brussels city is yellow and blue)
14. Peas?....(half moon for peas.....half moon all green...cause it looks like a fricken pea...look at the sunglasses)
15. Dill?....put this next since dill is a large temperature range herb....(double H for warm and hot temperature herbs....green and white....the color of pickles + the color of most pickle lids(white))
16. Basil...next just because I have no idea the order basill should be in...(single H...red and green...red due to basil being a good pizza sauce addition.)
17. Thyme...next just because I have no idea the order basill should be in...(single H...black and white...image of a black hole which has TIME altering properties)
18. Oregano....warmer weather herb....double H for warm and hot temperature herbs...red and green: red because oregano is a good pizza sauce addition)
19. Tomato.....(Circle symbol for fruits- red filled in circle with with white background looks like a slicing tomato))
20. Cherry Tomato....(Circle symbol for fruits �" purple and red circular symbol...Purple is the color of the stem of a cherry tomato
21. cucumber?.........or beans?...not sure which one requires hotter avg. temps(double Circle symbol for elongated fruits....double circle with Green outer shell + white inner shell representative of colors of cucumber.)
22. beans? Or cucumber...not sure which one requires hotter avg. temps(Crescent moon for beans, nuts,a nd seeds....Green with white background looks like a bean)
23. Peppers(Bell, then jalapeno, then serrano, then cayenne, then habenero)(X, XX, XXX symbols representation for peppers...green single X for bell pepper(color of bell pepper)...green double X for jalapaneo(color of jalapeno)...and so on)
24. Okra?....or melons?....not sure which one...according to slimy okra...this should be last..but other sources have some melons that require hotter temps than Okra(green star for color and shape of Okra)...
25. Canteloupe.....or Okra... according to slimy okra...this should be 2nd to last (Circle symbol for fruits...white inner shell + orange outer shell looks like cantelope)
26. Watermelon.....(circle symbol for fruits........ green outer shell + red inner shell looks like water melon)

???....Cauliflower....not in there yet...but I think it would somewhere between 13- brussel sprouts and 19.. cherry tomatoes)

Well thanks for all the advice and help everyone and if you have any temp or order info...or any other info...message back!!

So now we are talking about growing seedlings and transplants in a greenhouse for later transplanting to an outdoor garden, correct?

If so then that is a whole different discussion and I have to say based on over 50 years in the greenhouse and nursery business that you are WWAAAYY over-complicating the process.

First because you cannot control the air temps in a greenhouse to the various degrees you are looking for and second, because it sure isn't necessary.

What you can do in a greenhouse is keep it cooler or warmer than it is outside. However even with the most expensive, perfect, fully automated systems you cannot create 50 degree pockets in one corner or on one shelf while also maintaining 75 degrees in another corner or shelf. And even if it were possible the temps in those pockets wouldn't remain stable but would fluctuate hourly.

For air temps, the best you can do with all the proper equipment is create an environment within the GH that ranges no lower than 45 and no higher than 65. And that is the ideal GH air temp range for all vegetable and flower seedlings and for everything else that might be growing in there except for well-established tropical plants.

Don't make the process more complex than it needs to be. Trying to do so only discourages you and creates numerous additional problems for the plants.

Dave