Tender new citrus leaves have a much higher transpiration rate then do the older mature leaves. Therefore, the new growth loses water faster than the older growth, thus they wilt sooner. People worry too much about over watering container citrus trees. It is never the amount of water applied to a tree that causes trouble, it is the lack of oxygen that causes the damage. Therefore, if one tends to worry, then they should worry about how well the medium that the tree is growing in drains. If your medium has good draining you don't have to worry much about watering. Water is VERY important to a citrus tree--citrus trees don't eat, they only drink.

Makes sense. Mine's in decent potting soil, but am making sure the pot doesnt sit in water. Will try watering more. It'll be interesting to see what happens in summer, when the humidity here really spikes.

Thanks for the feedback!

Silica, thank you for that enlightening comment. I have been toying with the idea of growing a lemon in a pot (in my dreams it looks like those gorgeous citrus in pots in mediterranean resorts) and been reading all the various posts on potting mediums. Finally your comment above made me understand why people are so particular about the soil: the water needs to stay long enough for absorption, but drain fast enough for the roots to breathe. Am I on the right track? Kinda like earthworms drowning when it rains too much, even though they need moist soil to live in?

Kcandmilo: you got it ;)

Hold the plant up to a shaft of light and see if there is any webbing around the leaves or in the cracks where the branches meet. Spidermites and Thrips can cause distortion of new growth like that by piercing the cells in newly forming buds and leaves while feeding. Spidermites also happen to love low humidity and hate being misted. A bit of winter stress can cause huge populations explosions and eggs can last for up to 2 years. How often are you fertilizing and is it a complete fertilizer with micronutrients (copper, boron, sulfur...)? Have you added any amendments to the soil and what are the components of your mix? Sometimes soil ph can antagonize nutrient deficiencies and toxicities which could cause odd growth like that. Have you used any pesticides, or could the plant have been exposed to herbicide drift through a window from a lawn application or something like that causing phytoxicity issues?No guarantee any of that will help with a diagnosis but those were all the variables I could think of. Your plant looks healthy otherwise so keep doing what you're doing.