Mandarin orange not blooming

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My Mandarin tree is about 6 years old, grown in an unheated greenhouse in central NC.  It failed to bloom at all this year.The tree had about 25 oranges successfully  ripen a year ago December  (2020) . It's about 5 feet tall and multi stemmed. It had a few ripe  fruit the year before. I have not changed my fertilizing or watering regimes at all. The temp of the green house never falls below 35 degrees or so. It has  about 400 gal of H2O in black plastic 40 gal drums to temper temperature swings , and  I operate a small heater when
out side temps are predicted to be 20 degrees or  lower. It remains in the greenhouse year round. How can I wake it up?

How is this year different from last year?

Cooler temps in the greenhouse or less sun?

Trees start budding when the temperatures reach a certain level and/or the is plenty of sunlight.

To wake the tree up try to raise the temperature and get more sunlight by using mirrors.

I don't know much about trees in greenhouses or temperature though when I see a topic in the Zero replies I like to see if I can get other members' interest to try to get them to help.

Anne Miller wrote:How is this year different from last year?

Cooler temps in the greenhouse or less sun?

Trees start budding when the temperatures reach a certain level and/or the is plenty of sunlight.

To wake the tree up try to raise the temperature and get more sunlight by using mirrors.

I don't know much about trees in greenhouses or temperature though when I see a topic in the Zero replies I like to see if I can get other members' interest to try to get them to help.

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Thanks for the input. My dilemma is if things  were different I can't pinpoint anything . I just repotted   it to see if that helps. It was a real disappointment not to have it even bloom after the previous years  bumper  crop