The term Sorrento, I believe, is referring to the area it is grown. I also made the Costco purchase, back in spring of 2007. I chose the variety "Primofiore" and hope to one day make the limoncello. It was planted amongst our other lemons, and we have not seen much growth since. A few flowers appeared and dropped last spring. I am guessing that it will take a few years for production to "kick in". I have a Lisbon nearby with same MO purchased from Thermal Plaza. At that time we purchased a truckload of citrus from Thermal and YoungÂs nurseries, but only the Lisbon lemon is not doing much. But on the other hand, it took four years in the ground and a few years spent in the container for our limes to get going. The Sorrento lemon is mentioned in Julia MortonÂs book "Fruits of Warm Climates". 'Femminello Ovale'Âone of the oldest Italian varieties; short-elliptic with low, blunt nipple; slightly necked or rounded at base; of medium size; peel yellow, finely pitted, medium-smooth, medium-thick, tightly clinging; pulp in about 10 segments, tender, juicy, very acid, of excellent quality, with few, mostly undeveloped, seeds. Fruits all year but mainly in late winter and spring; ships and stores well. The tree is almost thornless, medium-to very-vigorous, but highly susceptible to mal secco disease. This is the leading cultivar in Italy, accounting for 3/4 of the total lemon production, and 1/5 of the crop is processed as single-strength juice. UCR also has the C. femminello ovale in its collection. It is located at "other lemons and hybrids". When looking at their lemons, only the Citrus femminello will pull up with info, but the "femminello ovale" is on the list without info link. It doesn't seem to appear in the CCPP; just the Variety Collection. It appears that patience will be required for these lemons; another year or two. I cannot locate the nursery tag, so do not know if the grower was mentioned on the Costco tag. Pam Here is a link that might be useful: European Citrus Page

Blurg, I really wish I had just sat on this for another couple of days. I chopped off the suspect branch this morning. I'm still curious though, so I have additional evidence to submit. Additional images are here: http://imgur.com/a/9avCc The only spot that looks like it could be the graft is just below the lowest branches, there are angles from different sides. I've also got pictures of the leaves and buds next to each other, and I popped open the biggest mystery bud and put it next to a lemon bud that had just started to open (I may have encouraged it a bit). If they're at different stages of development it probably isn't the best comparison but the stigmata look a lot different don't they? When I cut the branch, it did smell lemon-y, like pine-sol (my first uh-oh moment). None of the lemon branches have spikes anywhere near as impressive as the rogue branch, they're maybe .5-1cm on the lemon branches and sparse vs. 3-4 cm on the rogue branches and all over. I can't tell any difference in the petioles on the leaves, neither have obvious wings like some other citrus. If the branch were actually a water shoot, how much damage would I have done to the tree by chopping it entirely?

Hmm. It may be Botrytis. Lemons tend to be more susceptible to Botrytis than other citrus cultivars. You would want to treat with copper. You say you're in S. California, so I'm assuming, by your USDA zone (you should also include your Sunset zone, much more helpful), that you may be in an area that is close to the coast and has had a fair amount of rain, like me. http://www.ipm.ucdavis.edu/PMG/C107/m107bpfruitdis.html http://www.forestryimages.org/browse/detail.cfm?imgnum=1570469 May I ask you where you bought your Sorrento lemon? Patty S. Here is a link that might be useful: UC IPM: Botrytis in Citrus

I have grown numerous sfusato lemon trees from Sorrento, from Seed, its neatly impossible to get one to flower and produce fruit, you need to propagate from stems, that way you are reproducing the same tree, otherwise, from seed, you will only get a wild  tree