Fukushu kumquat. Mine do well in low light. None of my other citrus do. Sounds like you live in the Cincinnati, Ohio aria.

Steve

no I don't

my lemon seedlings I cut the top to make them bushy and only one is starting to branch out and I'm putting epsom salts into my home made liquid fertilizer for the magnesium

some body tell me if I'm doing the right thing

Adding any fertilizer if and when it is not needed by the tree becomes an overdose. Thus is not helpful, but is armful.

Can you provide a cool dark room where temps are in the 40's? You can make the trees go dormant and wait until Spring.

I can either provide as much light as the weather outside allows at around 73F or zero light at around 32F (maybe I can insulate them to keep them warmer than that, but I didn't think citrus could survive in the dark).

Most any citrus can be overwintered inside without much difficulty. Light rarely is the problem. Soil is a big one, overwatering indoors is easy. You need to a very well draining soil. If you aren't going the dormancy route keep the soil above 65 degrees. Watch out for mites as they love dry weather like houses are in the winter. Don't ferilize too much either.

that is the only liquid fertilizer it's getting

I've tried using LED lights one winter to prolong the number of daylight hours, but it didn't seem to make a difference. I am not sure what the issue is, but every year is pretty much the same. They do fine inside for 1-2 months and then they start declining until they're either dead or March comes around. That's why I suspect light is the issue.

it could be the brightness could be your problem

Some people here go the dormant route, I hope they reply. You sound like you have the conditions to do it, which is a option for some people. Alternatively, I overwinter with zero natural light, all lights. Many here do that too. My biggest problem besides bugs of every description, overwatering (not making the outdoor practically daily full sun in 511 to indoor change and its a big one) is ambient room temperature. My particular sweet spot where I get some growth, flowering and avoiding leaf drop is aiming for the low 70's on air (not easy with lights going on and heating system kicking in. I have to open windows and run a fan in the heating time hours. Keeping soil at 72 or so keeps roots active.

My basement is too warm to go dormant route......

When do you bring your trees in. It may be that one or 2 months OK before decline coincides with the heating system kicking into high gear.........some people (I own them haven't tried yet) use seedling heat mats to warm pot bottoms and saucers to keep roots warm and active to compensate for warm room temperatures. This helps avoid leaf drop.

The heating is definitely on when I bring them inside and temperature is pretty much always the same, so I don't think that's the issue. They're also kept on a table, so I believe the roots should be fine as well. I usually start seeing spider mites when they start declining. I don't think they're the cause of the decline, because you can't really see them when the plants look healthy, so I think they only grow in numbers because the plant is dying.

For keeping soil warm, check out brew belts, they are for home brewing to keep fermentation temps up but they work great for citrus. They sell on amazon for like $20.00.

You'd be surprised at indoor temperature DIFFERENTIALS. A soil thermometer meter or fancy laser can spot 20 degree variations between roots and leaves closer to the lights. If spider mites is the issue than weekly baths and near daily sprays with water or insecticidal soap go a long way. I know miss a few days and they come out of nowhere. Gotta treat plants before they come in. Anything small or not expected to bear fruit for a years or two can get treated with a systemic where the poison is taken into the tree itself.

Calamondin

Smaller fruit size = less light. Example limes

This is my latest fandango. An orangery on wheels. 140K lumen full spectrum light on a robotic light rail. $&@? the sun its optional! ☀️

Nice job Lemon.

Alex, try a hand at a Ponderosa Lemon. The flowers are huge, fruit huge and they still perform well with very low levels of light

Lemon. really nice work. Don't they also call those greenhouses.

they say ponderosa lemon is a hybrid

Kaffir lime if you don't have enough light for fruit. Use the leaves in Thai dishes.

If you bring all your citrus into the garage, when temperatures consistently go down, citrus will enter into a state of dormancy and will not need sunlight, because they can't grow or carry out photosynthesis anyway. Giving them light in these conditions will not help citrus survive any better.