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how cool at night for color to develop?
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Posted by hairmetal4ever Z7 MD (My Page) on Tue, Feb 2, 10 at 9:20
| Conventional wisdom (as I've heard it) says that for full color to develop on "orange" citrus, oranges and mandarins specifically, that winter nights should be cool.
How "cool" is cool? 55? 45? 38?
Looking at building a greenhouse, and trying to determine best temperature range.
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Follow-Up Postings:
RE: how cool at night for color to develop?
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| hair: I have citrus in a greenhouse. The Washington navels begin to turn color when the nights fall below about 50F. This is in late October. I only heat to 33F. So nights are cold by mid Nov and the navels color up pretty fast. My trees have done fine and the fruit is great letting it get cold at night. Obviously my heating bill is much lower. I couldn't afford to heat to even 55F and it's not necessary. |
RE: how cool at night for color to develop?
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| Good to know. The wrench that I'm throwing in is that I want bananas too - those are much more sensitive to cold. I might go with low 60s day, mid 40s at night...a compromise. |
RE : how cool at night for color to develop?
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| Do you heat over 33 during the day, or leave it there all the time? Solar gain will make days warmer, but here in MD, we only get sun about one day in three in the dead of winter. Ohio, where I'm originally from, was MUCH worse. |
RE: how cool at night for color to develop?
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| I have a decent citrus collection that are overwintered in a big garage. I minimally heat with a small space heater. Glass garage doors face directly south so temps will solar warm on sunny winter days (which have been rather numerous this year). The coldest it gets is mid to upper 30's--at night (minimum was 32 F. two years ago). Minimum day temps should be at least in mid to upper 40's. This time of year, my day temps inside easily get into the 50's to near 60 on sunny days (greenhouse effect). I think 33 F. day and night is way too cold for most citrus. Citrus so far are coloring and lovin' it! Good luck. |
RE: how cool at night for color to develop?
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| I never heat above that needed to avoid freezing. But we have lots of sunny weather all year so warm days are a given in a greenhouse. I do have about 60 days in winter where nights are 30s and days are as cool as I can keep it, usually 50s. This is to get needed chilling for stone fruit. Before and after chilling, highs are in 80s most days. I agree that 30s all day long for most days is probably too cold. They grow bananas in the central valleys of Calfornia. Not commercially but they can be grown. Ave winter temperatures are 30s at night and 50s by day. About 50% sunny days. Only frost causes loss. So you can go 30s at night. 50s most days would be nice for both citrus and banana. |
RE: how cool at night for color to develop?
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| The stimulus for color change is about 55 F. That means the fruit surface temperature must get that cold or colder. That will get the change from green to yellow or orange. Lower temperatures still, especially for extended periods of time, promote longer-chain carotenoids (deeper orange, rather than yellowish orange) color. |
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