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My experiencing of overwintering Citrus under growth lights

Posted by yellowthumb 5a Ontario (My Page) on
Wed, Nov 9, 11 at 11:18

I recently bought a gold nugget mandarin from four winds this summer. It's looking very good with many small fruits, I picked off all but 4. Late this summer, there are very many new growth. But the new growth grew very slowly, the new leaves getting bigger in almost one month time.

I moved it in my basement under a 1000w growth light, alone with many other tropical plants. But it's taking the prime location, lots of light. The temperature is in 78F when lights on and 68F when lights off. Humidity is low ranging from 40% to 50%. After about three days, most of the leaves except the new growth are drooping, like underwatered, but there is plenty of mositure in the soil. Plus, the lower side of the leaves started turning yellow in veins and gradually dropped. I immediated move it into my solarium, which will hot (85F) in the day if sunny, and cold in the night (60F), but humidity is around 40% in the day and 70% in the night. It recovered nicely, the drooping stopped, leaves stay hydrated even during hottest part of the day. There is no single leaves lost since.
On the other hand, my myer lemon, which has been with me the 3rd year, is doing splendid under the same light. No single leaves lost, exploded with fat fragrant blossoms. Leaves stay very hydrated.
Also, my improved myer lemon, sitting in a not so optimal location at the edge of the growth light, receiving far less light, sent out a several foot long new shoot with dark green leaves. But leaves are super sized, like my palm.

Now I do think that citrus will fair much better overwinter indoors if they already experienced the overwintering before. This also proved that they will hate the warm and dry conditions by shedding leaves or drooping their leaves if the lights is not optimal. Not even under a powerful growth light.


Follow-Up Postings:

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RE: My experiencing of overwintering Citrus under growth lights

What kind of soil mix are these trees in?

The Meyer Lemon that put out a long growth with large, dark green leaves is in need of light -
long growth is generally termed "etoliation," and the enlarged, dark green leaves are the plant's
means of capturing as much of the limited light as possible.


Josh


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RE: My experiencing of overwintering Citrus under growth lights

It's in the 5:1:1 mix.

Totally agree with you on the light issue. It wasn't sitting in the prime location before, that's why it's sending the long shoots with large leaves. Now it is.

On the good side, it didn't lose a single leave. Not like my gold nugget mandarin, sitting in the prime location and losing leaves.


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RE: My experiencing of overwintering Citrus under growth lights

Have you measured actual air temperatures near the leaves on the mandarin? Is it much taller and closer to the light? 1000w HPS or MH bulbs put out a *lot* of heat. The ambient air temp in the room isn't going to tell you the air temp near the leaves. If the gold nugget was significantly closer to the light (because taller) it's possible that either it was too hot (hard to do with mandarins) or that it was just transpiring more rapidly than you thought and the soil wasn't as moist as you anticipated.

It could also be that you had been over-watering it and then backed off when you moved it. Did you check the runoff water for the sour smell of root-rot? This might be the most likely explanation considering you saw veinal chlorosis? See: http://edis.ifas.ufl.edu/hs141 for comparison images.

It seems odd to me that the mandarin would do better with less light and colder lows. It is my understanding that they are often grown off the coast in more desert-like environments to help them sweeten up. It is also my understanding that 50% humidity should be plenty for a mandarin.

Is it possible that it was just shedding leaves in response to the transition from outdoors to indoors and then stopped once it had adjusted and the location was not the cause?

What kind of sun is the solarium receiving? How many hours a day are you running the grow light?

The vigor of the meyers doesn't surprise me at all - they always seem more vigorous to me but the situation with the mandarin is surprising to me and I'm interested because I'm currently over-wintering 5 mandarins...


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RE: My experiencing of overwintering Citrus under growth lights

The mandarin is about 4 feet from the bulb, the air temperature is pretty high. If I put my hands there, I can feel it's pretty warm.

I may have over potted it a bit, of course, that will be easy to over water it. But there is no sour smell in the run off water.

The solarium is south facing, but the glass is cutting off about 40% solar heat. But we have pretty short days, it's pretty getting only 4 or 5 hours dappled sun. That's it.

I keep my light on for about 13 hours a day.

Thanks for the help.


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