Citrus only changes color in cool/cold weather. Since you move yours inside in winter, the fruit doesn't change color. Of course you can't leave it outside in winter. You just have to accept that the fruit won't change color. That doesn't mean it isn't ripe. So try some of the older fruit. A lemon is ripe when it's big enough.

My citrus is in a greenhouse that is only heated enough to avoid freezing. The fruit starts to change color in Oct/Nov as the nights fall into the 40s and 50s. They fully color up with lows in the 30s. If you get your tree that cool in winter the fruit should turn yellow. But it's not necessary for useable fruit.

The Fruitnut

I grow Ponderosa lemon and calamondin orange and both ripen around Thanksgiving. The calamondin ripens all year but everything on it ripens in November. My greenhouse is kept cool. I don't heat except when the temps go below 35*.

Ditto! My oranges and meyers ripened once they were exposed to very cold weather..

I have to disagree fruitnut. Citrus do not change color due to cool weather. In fact, the same variety planted in 2 climates will turn color earlier in the warmer climate. Some varieties do not color up until it starts to warm up the second year, after the second year's blossom is done. Color is by variety and getting enough heat and growing season.
More likely it's still green because it's not getting enough heat for enough days.
You say 2 years, like 24 months and a full 2 years? or more like 15 moths into the second year? If more like 15 months, wait until the next warm season, they may still ripen.
If it smells like lime, it may be lime. But even lime will turn a lighter green, to even yellow when really ripe.

First, realize that "ripeness" and peel color are independent of each other in citrus. But secondly -- in the case of oranges and most mandarins, it is indeed cool weather that triggers the color change -- specifically temperatures below 55 F. In grapefruit, lemons, and limes, however, cool temperatures are not required.

Thanks Everyone for the Help

I also have lemons that won't seem to change color. I'd assume they are only 4 or 5 months old as they were only 1/4 inch whe I got the tree. I hear it takes around 9 months to mature. It is now late October and blossoms have begun to open in the cool weather. Once temps reach around 50 in the daytime I'll bring it inside full time, otherwise I'll cover it. I'm in zone 6

Dent,

Those lemons are most certainly not mature... maybe 2-3 months more.

Color in citrus is the result of cooler nights; but the most important factor is the difference between day and night temperature.

How wide a temperature difference does there have to be? My grandmother's lemons are starting to turn yellow now, and we've had not had more than a 10-15 degree difference between day (mid to high 80s) and night (mid to high 70s) for a few months. Same with her tangerines.

Some varieties will yellow easier; and some will just get a yellow-green. For Meyers you normally need about 25 degrees F difference for good coloring.

I'm in zone 5 and have had a Meyer Lemon for 2 years now. My fruit still hasn't turned yellow at all. We recently brought my tree inside due to the weather change. should we leave it outside to ripen?

My lemons are still green...and that's normal. Mine don't color until almost Christmas and don't get good for picking until Jan/Feb. I think it is a Lisbon. Temp doesn't matter for the ripeness or color for the variety.

Meyer might be a bit different as it is part orange.

I have read most of these post...yet I still do not seem to see an answer for me...I have lemons, maybe a handful that have been growing for almost 10 months! and still are green as grass....Are they ripe? Can I eat them? Or do I need to just say "Hey, it will take a year and a half to get a yellow lemon?"..it is for sure a meyer lemon plant..*sigh* Oh I live in mid to north Georgia..Highs are low 90's and cools are 68ish..

Try one!

Beverly,

Can you post a closeup foto of the fruit; most citrus change appearance when they are ripe or near ripe, irregardless of the color.

My lemons always change color for me, I do leave them out until late September-early October with the temps into the low 40's. My container tree is so off schedule though that the lemons don't fully size up or ripen until the following summer.

How cool are you all talking about? We don't go down below 50 very much, except for January, and we live in citrus land! I always thought it was heat that ripened them, so am reading this thread with great interest!