hi, Happy Birthday to your wife. I will give you my experience and what I have been doing with mine: I bought a meyer lemon in i think sept/oct 2007. it was outside until the frost came. now it is in the basement under a 42w CFL (compact florescent light) and it has started to get new flower buds and the lemons which were on the bush is still ripening. I have an calamandin orange tree at the northeast window upstairs in the winter. (it is outside during the summer)i don't augment the light on this one -and I have had this tree for approx. 7 years. we get alot of cloudy days here during the winter. the orange tree also has flower buds and little oranges. i use azalea food, epsom salt, and fish emulsion, and teaspoon of vinegar in liter of water. i spray the leaves with misture of half teaspoon pure neem oil, couple drops liguid soap in litter of water at least once a week to avoid getting spider mites, aphids, etc. When i water, i make sure i water enough that the water comes out the bottom of the pot. i also wait until the soil is barely moist before i water again. good luck with it. hopefully others will come in with their advice because everyone grows their plants slightly differently. Happy Hoildays.
sue

Hi Wp..It's been so gray in our part of the globe, even setting a plant in an unobstructed south window has little effect..(S)
My citrus (those not in a small gh) are placed directly in front of south windows.
One advantage of living in a condo, the higher up you are, the better light you get. How far apart is your unit from the other side of the building, facing south?
IMO, artificial lighting isn't enough for a sun-loving plant such as citrus..If by chance you have the light/fixture hanging in front of a window, this will certainly be beneficial, but natural light can't be beat..Especially if you'd like your plant to flower/fruit.
Right now, this time of year, there's really not much to do with your citrus..
Most important is light..try supplying as much as possible, though it's difficult in Il.
Proper watering is mandatory. Like Sue stated, you want to water thoroughly till water seeps out of drainage holes. Before watering again, be sure the soil is on the dry side. If necessary, buy a water guage, but the easist and inexpensive way is sticking your finger in the soil. If your finger comes out dry then water, if wet, wait a few days and retest. Lifting the pot to test weight is another way to check but I prefer the finger method. Never keep the soil muddy, or sitting in water.
Citrus like humidity..a humiidfer works best..(for people, also) I mist daily, plus try hosing in sink/tub once a wk. Most people don't bother, but it's something I like to do..it helps keeps foliage clean, removes dust, and gives one a chance to inspect leaves/stems for insects. It also helps increase humidity.
What size pot did your citrus come in? I hope you didn't overpot..it's normally best to increase 1-2 sizes up..
Soil type is another very important matter..A well=draining soil is best..something that's not going to stay wet despite heat, dryness and time.
What type of soil did you use? Did you mix your own or buy packaged. I mix my own using (I'm sure some will disagree, but it's what works for me) all purpose, sphagnum-peat, sand and Perlite..sometimes a little added charcoal/large bird grit/orchid mix.) Sand(Builder's Sand from Home Depot, not beach sand) orchid bark, and Perlite helps with drainage.
Do not fertilize this time of year. Usually, it's said a plant doesn't need food after repotting in fresh soil.
If you don't have citrus fertlizer you can plan ahead, and order before spring...Have you ever shopped at Jamaican Gardens in Morton Grove or Libertyville? I'd call ahead, but they had citrus fertlizer available..they also sell beautiful plants, including citrus.
You can always substitute using Azalea or Palm food. Don't bother with spikes..they're a waste of money and time. And don't work.
Certain nurseries on Ebay sell Citrus fertilizer.
There's more to growing citrus, but for the time being, the main thing you need to do is offer sun/light, water, and provide humidity.
I hope your wife had a Happy Birthday..Nothing better than a citrus for a birthday gift.. Meyer's are fantastic.
Good luck, Toni