That's what thinning is for. It's still not too late to take off half the fruit. This not only avoids broken limbs but improves fruit quality. Prune back as far as needed to stiffen up the limbs. Also clean up broken branches. You can also prune back as needed to make thinning and harvest easier.

dad had one here in MI for 20 years.... only twice did it set fruit ... the blooms are extremely touchy in terms of temps .. the slightest frost will make the flowers abort ... so that would be the simple suggestion as to why it fruited one year.. and perhaps not the next ... even in CA .... [any recollection of the citrus folks going crazy.. the year it did not set fruit????] i would suggest that a 2 year history is not enough info to jump to any conclusions ... and surely not a reason to leap to pruning to solve the problem... which it wont.. if it was a temp issue .... also.. pruning for fruit production.. usually does NOT make for a pretty tree .... if you are not the owner.. its really not your problem ... and i dont know why you would want to interject the topic into your landlord/lessee relationship .... the tree is grossly large for such a tiny space ... if you consider that the root mass could be twice as large as that above.. you wonder where it is getting water and air ... as compared to all that concrete ... at least its not a 100 tree.. that will crush the house ... killing you in your sleep ... if it fails.. it should not do that much damage .. and its not your problem anyway ... if i were the landlords ins agent.. i might not be happy about the risk ... also.. sooner or later.. there is the possibility .. that it might cause those walls to fail ... the only issue being.. in whose lifetime ... lol ... i only bother to mention all this.. because you had a thirst for knowledge.. bottom line.. i would not invest anything in this tree .. and be saving money for future removal ... as even i dont think i could get it out of there safely/easily ... i have 5 acres.. and CA lot sizes mystify me ... thats quite a front yard you have there.. lol ... but at least you have one.. compared to apartment folks.. if i had that tiny a spot.. i would have some type of potted collection of plants to play with ... rather than two 20 foot trees ... have a great day ... ken

Lisa, if it was mine, and I wanted it top branch out more and be more bush like, I would cut it off at about 16" above the soil line. Now is not the best time, but will not hurt the tree long term, and will get it headed ion the direction (shape) you want this season. When it is dormant, prune each bra nch back to 2-4 leaf nodes, which will encourage further branching next season. These are inground tress, but give you the idea: http://forums.gardenweb.com/forums/load/fig/msg0100594215655.html http://forums.gardenweb.com/forums/load/fig/msg0101490623831.html

Snipping the tips of the roots when planting a bare root tree can help stimulate the tree to push out more roots at the pruned point. It can help with badly root bound trees to encourage the roots to splay out also. So yes, you can prune the roots however if your aim is to get the tree to flower again, that won't happen this season. It's done flowering and probably won't bear any fruit for the new 2-3 years while the root structure is growing into its new home and the branching structure is establishing. I'm sure it will flower next year but the likelihood of seeing any fruit is slim.