So you're saying from looking at the pics and the information I've given, the only reason the leaves have all dropped off is because I changed the light conditions?

I live in London so at the moment the weather isnt great and the sun is barely out, which is why I bought the grow light. Should I leave it under the grow light and continue giving it 10 hours of light a day? Obviously when the weather gets better it will go outside. Would building a small glass greenhouse for the tree make a difference?

Also, how do I know if the fruit is edible or not. They aren't firm to touch and dont look that edible unfortunately.

Thank you for your advice, it's greatly appreciated.

I give my trees 16 house of CFL light

New Zealand lemonade#1 · More Info

The fruits are great. Don't change the light conditions again; the tree is already in shock. Wait until Spring; and then put it outside gradually, as explained above.

Where temps do you get where you are? What is the coldest in winter?

To me it looks like you either let it dry out way too much, burnt it, meaning the roots or the leaves, over watered it or used too much fertilizer....Mines have never ever took to crispy like that from light change at all.

I will tell you that you have the nicest fruit and at one point that tree was doing awesome..

Stick around and let us know how it does..Very nice to meet you)))

I agree. Remove fruit. It's ready to be picked.

James. I agree with all the remarks thus far. I also believe this species of lemon is touchy to temp. changes as well, which begs the question of, what is the outside temp. when you open the window and turn on the fan? Good air circulation is important, but not for the problem in the pic's. That said, I looked at the grow light bulb you are using and feel it might not be enough additional light and the bulb could be to far from the plant. I have had the same problem in the past and the more light intensity the better as long as you increase it, as mentioned, in about two week intervals. Since the leaves are going from green to brown, I believe it's not a water issue. As well, at those temperature levels it seems the fertilizing should have been all right if the light levels were consistent. I have had some luck using foliar sprays, in lieu of, or in addition to watering. They do like their humidity.

The temperature at night outside can go down to -1 and during the day I guess between 6-11 maybe. I only have the window open for 5 to 10 mins. And if I'm being very honest I don't always do it daily.

On the subject of honesty and I feel slightly stupid for saying this... But I'm actually not sure how much water you're supposed to use when watering. So everytime I've watered the tree I've used my blender jug as it's the only thing I had to hand with measurements on it. And I've filled it up to 500ml and given that to the tree. The tree is balanced on a few stones in a tray so water comes out the bottom and stays in the tray away from the base of the pot. I searched all over the internet to try and find out how much water to give it but I couldn't find any information. So when it came to giving the tree winter citrus food the instructions say 1 level teaspoon per 2.5ltrs. So I divided 2500 by 4 and 5 (teaspoon in ml) by 4 as it made sense to divide them both by 4 to get that I should put 1.25ml per 625ml. (I'm really bad at math.) So I could have overwatered it, I'm not sure, I did check to make sure the soil on top was dry though before watering.

The grow light is 40cm above the tree.

Thank you all again for all your help it really is priceless.

If you are in the northern hemisphere, you should not be fertilizing in the winter because fertilizing will encourage spindly, weak growth.

Use enough water so that you can cover the entire surface to wet the surface and have about 200 mL of water drain out of the bottom of the pot. Once a month, place the pot in the sink or bathtub and pour a bucket (about 8 L) of pure water (without fertilizer) to rinse out any residual salts that may have built up.