Lemons losing all leaves

Question

I've been trying to grow some lemon trees from seeds. Everything went mostly fine: out of a dozen germinated seeds I got 5 seemingly strong & healthy saplings growing. These are the saplings after about half a year:

However, after a few more months they started to gradually lose all their leaves. This is how they look now:

Presumably, some of them are almost dead by now. I initially thought that temperature might be the problem, but I'm not so sure about it now: weeks of warm (+20°C - +25°C) weather didn't stop the leaves from falling off. So, my main ideas for what caused this are:

• Hard water. I used water from a regular tap, which might have too much minerals in it. You may see some sediments on the soil. The most sediment appears to be on the soil with the most up-to-day healthy plant, - presumably it got less minerals dissolved inside the soil.
• Bad soil. I used some general soil from local gardening market, nothing special.
• Bad lighting conditions. I have one table lamp (something like the one on the picture below) lighting the lemons directly from above, roughly 16 hours a day.

So, my questions are:

1. What is the most probable cause of the saplings losing their leaves? How to prevent this in future?
2. Is there any chance I could save the two saplings that still have some leaves on them and haven't dried out yet?

Answer 1

We can see from the leaf base marks on the stem that the leaves were naturally separated and discarded by the plant. This may be an over-reaction by the plant to too much water. Citrus plants are known for "leaf drop" when they are too wet at the roots. Think back to your watering practices and recall that many citrus plants grow in quite warm countries where rain is infrequent. It's possible you were too kind to them. As young plants the roots were still high up in the root ball; as they got older and filled the pot they became more aware when the soil was wet. Possible?

Answer 2

I see two issues that might be the cause of your project gone sour. First, the light seems not professional grow light, but just normal light? Plants need special grow lamps, there are cheaper LED alternatives now.

But I think the main cause of the leaves drop is humidity. When you grow them indoor, the air is too dry for most plants. You can try to humidify them with a humidifier or by spraying them with water once in a while.

Answer 3

I agree with the above statements, combination of overwatering and poor lighting, with the emphasis on the overwatering part. But what I would like to contribute is that planting them in a bigger planter WILL help, as long as you don't water them right after planting like you usually would. The surrounding dry soil will take up the excess water and the soil will dry out faster because of it. Also refrain from plucking open the roots, which you normally also would do. Since the roots have already been through a rough patch, I would leave agitation of the rootzone up to the soil this time.