Hi, I've never heard of a Ponderosa lemon (only a pine, or a ranch :-) but what you're asking is for an instant course on a big subject. Bonsai does require more than a couple of tips here, but it's not hard to get started, especially if you already have a healthy tree (plant) to begin with. The quick answers are yes, you have to cut the roots and (in time) use a small pot, but there's a lot to know about those steps, when and how, and which one, etc., not to mention things like lighting, humidity, etc., though you're obviously doing something right to have kept it going this long. It's also very important to know when and how to cut back, because doing it at the wrong time and indiscriminately with regard to what's cut aren't going to get you a nice tree, just a hacked up shrub. I suggest you try to find a bonsai club nearby, because it's the best way to start out... by actually seeing how things are done, finding out about watering (a very big issue in bonsai, which are not treated like house plants), soil mixes (very important too), and what makes a bonsai look good (or not) and why, plus how to do root work, etc. Until then, please don't just stuff it into a little pot as you'll likely lose it, and ditto for root chopping. You can go to www.bonsai4me.com for general info. on basics, www.bonsaitalk.com to ask and share info., and www.bonsaihunk.us/cultural.html for excellent advice on growing tropicals indoors. One thing I will tell you is that bonsai come in all sizes, and that fruit and flowers won't 'reduce' in size like leaves, so you may end up with a relatively larger tree (which is fine) if you want to keep a few lemons on it at any time, or else end up pinching off new fruit buds to keep the tree's energy into growing a bonsai and not to have lemons weighing down branches (or breaking them) all out of proportion to the rest of the tree. Come back and let us know how it goes!

You might not want to keep the best plants in the window for very long. The lights can actually produce a more robust plant than the window, that's one reason why a lot of people use them. If you don't have enough room under the lights and need to use the window for extra growing space, I would plan to rotate the plants every couple of days from one location to the other so that they all regularly spend some time under the lights. Rearranging them periodically will also help them grow a straight stem, since plants tend to lean toward the direction that the strongest light is coming from. For your window this will be the outdoors and for the light fixture it will be the center of the fluorescent tubes, because even though you may not be able to see it, the light intensity falls off dramatically as you go from the center toward each end of the tube.

A few plants in my garage. South window, fluorescents on timer + a 1,000 watt metal hallide lamp set to only 4 hours (otherwise too expensive). Temp around 50 to 60 degrees. Nice and chilly = very few bugs and less watering! Oroblanco fruit growing slowly ↓ May be ready by spring? These are the first fruit from a gifted rooted cutting. Key limes ↓ Most have fallen and landed in a key lime pie, which was utterly amazing! Clem-Yuz ↓ More Clem-Yuz ↓ First time this seedling bore fruit! Only a few fruit left to eat! Like a somewhat tart but seedy (10+ per fruit) Clementine. Juicy, easy to peel and full-flavored. A keeper, I think. Not sure it's 100% Clem-Yuz. But who cares, if it's good? Owari satsuma ↓ Fruit all eaten now. So-so fruit quality, but it's a young plant. Armstrong satsuma (photo taken in October) ↓ All fruit is eaten now. Exceptional fruit quality this year.

purslanegarden - I had the specs on my lights when I bought them but don't recall them now - I know they are sufficient to grow a variety of plants (I bought the setup from a place that sells cannabis supplies) - and as I said I do grow many indoors under grow lights - my lettuce are the only ones that suffer. I didn't move the lettuce from germination to now - maybe that;s the problem. They were probably 6 inches from the lights at germination. LoneJack - thanks for the info! I figured out after a couple of people mentioned Johnny's seeds what it was - I hadn't heard of them before - I am new to growing from seed. They are pricy - i will definitely buy from them once I am done with my current seed stock. I would like to buy onion starts from them though!