Prune it lightly and see ow it goes. If you aren't satisfied, try again. Do bear in mind that pruning too much might set it back from fruiting, so don't prune heavily. Citrus also fruit only on new growth, so don't prune too much of the new stuff off. Wat it probably needs is a good feeding regime - it will produce a bad crop if it doesn't have the right fertilizer regime.

Pruning out crossing and inward growing branches is almost always a good thing. Those water sprouts could go, too. Just don't take out any of the primary branches or do any 'topping' while you're pruning. I don't think that I would worry about every little twig. Walk around the tree so that you are pruning from all sides, and take you're time. Pruning is a 'zen' thing for me.

Be sure to prune each branch at the branch collar (see link) so that you never leave a stub. Flush cutting isn't good, either.

As long as you finish up your pruning this winter, you shouldn't apply any pruning gunk. Pruning paint does nothing to prevent 'infection', as you say and may even hinder the healing process. However, late spring and summer pruning cuts should probably be painted in order to protect the tree from citrus borers.

By the way, be sure you have the right tools for the job. Sharp hand pruners (the by-pass kind), loppers, and a good little pruning saw should do the job, easily. I have a small folding saw that I use for almost every king of pruning.

Here is a link that might be useful: Click here

Thanks for your replies.

aesir22, is there a particular fertilizing product that you would recommend?

rhizo_1, what do you mean by "topping" the tree? Do you mean randomly cutting the branches short?

I am not the expert when it comes to in-ground citrus. Feeding them is different to potted ones. There should be someone here who can answer if you post it as a new question. Either way, they are greedy beyond greedy and need lots of food. Especially to produce good fruit. If the lemons are huge, they are likely ponderosa.

The best ratio if 5-1-3 NPK with trace minerals, but for the quantity and timing with in-ground, I'm afraid I don't know.

Okay, I did it. Pruned the tree down by a moderate amount. There were quite a few water sprouts that had to come down - it's amazing how tall they got. Lots of interior branches came out too. It was impossible to remove all the crossing branches, as some of them had because quite large.

I figured out what topping means, and it appears that the previous owner (or rather, her arborist) was guilty of this. A lot of the water sprouts arose from the ends of suddenly truncated large branches. I'm not sure if anything can be done about these.

The tree looks better. The foliage is thinner than I expected at the end, but I think a lot of the greenness was due to the interior twigs that I removed. We'll see how it fares this season.

Thanks again for your help.