David gave me an improved meyer lemon tree for our three-year anniversary. We've got it on the porch in a terracotta pot, against the wall of the house. It has one small green lemon on it, and it appeared to be adjusting okay. The past few days, though, I've noticed its leaves curling, yellowing, and dropping.
Some cursory online research leads me to believe that it's one of three problems: aphids, overwatering, or lack of nutrients.
Aphids are a common citrus tree problem. I inspected the leaves of our plants for evidence ("honeydew" or stickiness on leaves) and found nothing. If it turns out we do have an aphid problem, the best solution (apparently) is Neem spray. I highly doubt we're overwatering (we've been watering about every other day and it's been hot as crap), but I'm going to purchase a moisture gauge tomorrow just to be sure.
Hoping for the easiest fix, I spread some rhododendron (high-acid) fertilizer along the edge of the pot tonight. Fingers crossed this works.