My Lemon tree has lost most of its leaves,Its indoors,I am spraying it daily. what am I doing wrong,How can I bring it back to growing
again? The tree is about 4 feet high and still has lemons on it,but not many leaves and no flowers.
Certified GKH Gardening Expert
Trying to grow a citrus indoors without at least 200 watts of horticultural lighting per tree is the most common mistake gardeners make with these trees. They will not produce, and will always lose leaves during their stay indoors. With no leaves there will not be enough energy to sustain flowers or fruit. Those that are on still will likely abort unless you can get plenty of leaf growth back very fast. The only way to do this will be to put the tree under 200 watts of HORTICULTURAL grade lighting.
The type of light that you use will dictate the distance that you will hang it from the tree. The only way to know for sure will be a PAR meter, which will be very expensive. The next best thing will be trial and error.
If you are using HID bulbs, such as metal halide or high pressure sodium, then you can gauge how far you hang them by feeling the light emitted with the back of your hand. If it is hot, then it is too close. It should feel slightly warm but not hot. These will usually require heavy ventilation to avoid overheating.
If you are using LED, then hanging height will be dictated by manufacturer and quality of the LED. Good quality LED's such as KIND lED will require you to hang the light AT LEAST 3 feet above your tree to avoiding scorching by light intensity. They do not, usually, require any extra ventilation, however. I do not recommend cheap fixtures, as they aren't even worth their $100 price tag. Unfortunately, a good LED in that intensity range will run roughly $600. If you choose to go higher in intensity, you can light many trees at once. For example, a 750 watt led can support, roughly, 4 citrus comfortably. This will run about $1300, though.
There are many options available, but one thing is for sure. If you have to bring your citrus indoors at any time, then they will not fruit unless they have enough light AND humidity, so you will want to keep this up as well.