I was wondering if anyone out there has used a LED light to grow citrus during the winter? I have read many posts about how the WLD occurs when the leaves receive direct sunlight while the roots are cool. I purchased an LED light and placed both my lemon and lime tree in the garage where it seems to be maintaining the roots at around 65 degrees. The light gives off very little warmth at all so the leaves stay around the same temp as the rest of the garage. I have been placing the trees outside during the day when it is cool but sunny and inside the garage at night since there is a growing issue of frost. This week will be the first when the trees are inside the garage around the clock. I am setting the grow lights to stay on for 12 hours to simulate outside conditions. I have had a few old leaves fall off (at the bottom), but the trees seem to be growing new leaves and otherwise look very healthy. My lemon is 2 years old now and I lost all of the leaves last year and the branches to boot! I feel a bit more optimistic this year, armed with all of the great information I have found on this site. It's funny how these little trees can cause such anxiety! I have yet to harvest any lemons and hope that this winter will be different!
Don't feel bad . I have an orange tree that is 15 years old and has only given up 2 oranges about the size of a quarter. Man, they were so good. Sort of an apology I guess. <g> Bob
If your intention is to obtain growth throughout the winter months, you really have only three choices when it comes to artificial lights appropriate for indoor growing, fluorescent lights, High Pressure Sodium (HPS) lights and Metal Halide (MH) lights. (HPS and MH lights are sometimes referred to as high intensity discharge (HID) lights. These types of lights produce acceptable spectrums for plant growth and are also efficient in turning electricity into PAR light so they are cost effective compared to other light sources. Plants do not see light the same way that we do. Plants are less concerned with how bright the light is and are more concerned with the energy of the light. - Millet
Bob-- I aspire to have a few lemons at some point! As a teacher, I value the learning experience of losing a few seasons, learning some more, trying again, etc... As a novice, I'm a little less patient! Hopefully time will work in my favor this year and I will have something to show for my late night researching in the next few years. :) Millet- I guess my intention is really just to keep the branches alive this year! Sounds like a simple goal, but you had to see the sad carnage of last winter to understand. The grow lights came recommended by a horticulturist and is called a glow panel. There is a ratio of red and blue light that is supposed to be good for plant growth and fruiting. I have been assured that if it doesn't work out, I can return the light. I have managed to research a tad bit on the other light sources (halide), but they are currently a bit out of my budget. I will continue to research and hopefully can afford them in the near future, especially if the glow panel doesn't make good on the horticulturist's claims. My original question still stands, does the roots need to be warmed if the leaves are receiving light (but not heat)? Would that mean that the evaporation off the leaves would be less so they wouldn't fall off?
If the leaves warm to the point that they transpire moisture, the roots need to be 64F +. If the leaves are kept at a cool temperature where they do not transpire, than the roots do not need to be heated, but should under no circumstances freeze. If the roots are kept cool, the tree actually does not require much light at all. - Millet
One of the problems I seemd to have was that the tree would flower at the wrong time of year ie. early fall. The ensuing darkness seemed to make the fruit buds fall off despite my efforts to pollinate same. I keep my green house fairly cool but am now considering increasing the light values for a good period of the day . Bob
Millet- Thanks for the information about leaf transpiration. I teach 4th and 5th grade in Washington state and this is definitely a topic of discussion as we learn about photosynthesis! I am very pleased that my garage will keep the trees at a temperature where they will be safe from WDL. Will the trees still have new growth with light, but roots around 64 degrees? Does the cooler temp (low 60's) put the tree in a state of dormancy? Will the fruit that it has still develop under these conditions? If not, what is your recommendation for warming the roots? I have read about using Christmas tree lights, but I'm a little uncertain about their safety. Have you had much success/experience with heat mats? Sorry to be so inquisitive. The limited information I know about this is in direct relation to the curriculum I teach my classes. Transpiration and tree dormancy are usually discussed at the leaves drop from the trees in the Fall. I appreciate you sharing your wealth of knowledge about this! Bob- I have had the same isssue with my citrus trees, but I think I have read that it is natural for citrus to put out a 2nd crop of flowers (smaller amount though) in the Fall as well. Since my tree was recouperating this spring and just putting out new growth altogether, I didn't get any buds until late summer. Now my tree is covered in new growth (fresh leaves showing up every day!) and buds as well. Last year I knew that this was a sign that the plant was stressed and not doing well (leaves were dropping at an alarming rate while buds were setting.) This year, the tree looks healthy. I'm hoping that I will be able to keep the new fruit from the Fall over the winter and have fresh lemons to harvest sometime next year! Good luck with your orange tree. It sounds like the extra heat and some light might be the trick for you as well.
Steph, the root system of a citrus tree completely stops all functions at temperatures at or below 55.5F. The foliage of a citrus tree, becomes "dormant" at 64F. Therefore if you wish your tree to continue its growth throughout the winter, the root system must be maintained at temperatures above 55.4F. For any type of quality growth, I would recommend a minimum root temperature of 64F (70F would be much better). Water resistant heat mats work very well, especially with some sort of cover over the top of the container to help insulate the medium from losing heat. Many times during the winter, citrus fruits dry out on the tree and drop if the tree is stressed too much. So for fruit development and fruit maturity, higher temperatures and good leaf activity should be maintained. Irrigation with a nutrient solution should be done ever in winter. Your other option is to keep your tree at a cool temperature with minimal light, as discussed above. I currently grow nearly 100 varieties of citrus trees in a large greenhouse in Colorado, and maintain growth year around. By doing so my trees average 5 growth flushes per year. Good luck. Be the best teacher you can be. - Millet
Dear Millet! Wow.. what an educator you are! I so appreciate your patience. Thank you for clarifying the items that I have been so confused about. I cannot believe you grow so many varieties! That is amazing. I aspire to at least grow one or two varieties at my home and one day figure out how to keep one in my classroom for teaching. That, I imagine, is a long way down the line, but we all have dreams :) I will be researching heat mats more to find the best one for my trees. I feel so optimistic about the winter's outcome now! P.S. I have already turned my class onto this website and we are currently using it to learn about how different plants grow! Sometimes the best teachers are among us in the places that we can neither visit or, at times, fathom. Thanks for all that you post!
