The Tropical Fruit Forum
Citrus => Citrus General Discussion => Topic started by: Vlad on January 04, 2018, 10:23:26 PM
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My greenhouse contains seedlings and trees that are up to 10 years old. I would like the greenhouse conditions to be favorable for rapid growth of the seedlings and for maximum fruit development of the older trees. What temperature settings should I use for the day and for the night?
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For some guidance you may want to take a look at this http://www.crec.ifas.ufl.edu/extension/trade_journals/2011/2011_Nov_root_temp.pdf (http://www.crec.ifas.ufl.edu/extension/trade_journals/2011/2011_Nov_root_temp.pdf)
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Thanks Isaac, good article.
Cory
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Thank you Isaac for the article. I am sorry I was not clearer in my post. The article states that maximum root growth occurs at temps between 72 and 81F although I recall that citrus roots function properly down to 57F. So, for my 1 – 3 year seedlings, I would ideally want to maintain temps between 72 and 81F for maximum growth, presumably day and night. However, I believe my older trees require a cold period to induce fruit set. If so, what are the day and night temperature requirements and the duration of these temperatures?
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To induce a very good flowering in citrus ---- 2 weeks at night temperatures between 50 to 55 F, and day temperatures between 59 to 65 F.
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I have no problem maintaining night temps between 50 to 55 F but day temps often go into the 80's , sometimes higher (depending on outside temps and amount of sun). Would the higher temps interfere with flower induction?
Also, would maintaining the greenhouse at these temperatures all winter interfere with flower induction?
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With low night temperatures, and higher day temperatures your trees will still get a bloom, however the tree will have both a smaller number of floral shoots and flowers per shoot. In areas such as Florida and other semitropical and tropical citrus growing areas, winter water deficit stress is imposed on citrus trees of all cultivars to compensate or inadequate exposure to low temperatures during their mild winters. One last note: citrus are day neutral, meaning that day length does not induce flowering as it does in many annual and biennial plants.
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Millet, thank you for your replies.
I decided to keep the greenhouse temps set at 55 F and allow daytime temps to reach mid 70's due to solar heating. I will move the seedlings out of the greenhouse and into my home and put them under lights with temps of about 65 - 70 F in order to get maximum growth.
Does this sound like a reasonable plan?
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If the plants are going through Winter in a state of semi-dormancy the minimum temperature should be about 50 F.
To grow, citrus needs a minimum temperature of about 65-70 F. The growth rate will be nearly twice as fast at 80 F as it will at 70 F.
It is okay for the temperature to go down in the night but generally you don't want a temperature drop of more than 17 degrees or so (between day and night) because that can encourage leaf drop. At about 89 or 90 degrees I'd start being concerned about overheating.
Seedlings should probably be kept above 68 at all times, and prefer a warmer 76-79. Too hot isn't necessarily good, it can cause the soil to dry out or encourage root rot of the seedlings.
(all these numbers are very approximate)
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Millet, you said:
To induce a very good flowering in citrus ---- 2 weeks at night temperatures between 50 to 55 F, and day temperatures between 59 to 65 F.
Is it too late to do that? At least half of my trees are already flowering.
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What if your tree,s has a lot of fruits going into the winter months, do you maintain a certain temp in your greenhouse?
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Vlad, if your fruits are already flowering it is too late, try next year. In my greenhouse, I set the thermostat at 55-F for the entire winter, and the day time temperature is whatever it is due to the sun light.
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My heater's thermostat is set to 35F for several reasons - to save on propane costs, 2. growth is regulated by photoperiod with citrus. It's a phytochrome, hormonal accumulation thingie. You must have long days and short nights AND warmer temperatures to induce active growth. Accordingly, you're wasting your money on fuel regarding citrus especially in Maryland.
http://www.crec.ifas.ufl.edu/extension/trade_journals/2010/2010_Nov_supplemental_lighting.pdf (http://www.crec.ifas.ufl.edu/extension/trade_journals/2010/2010_Nov_supplemental_lighting.pdf)
Mark