Thank you for sharing your question about pruning your orange trees.
Here is what you asked:
"Where to best prune our orange trees"!?
Orange tree pruning - The trees in your case, are fabulous! and with your permission I'll begin by trying to diagnose the situation (under the limitations of distance and digital :-))). First, what I can see clearly from your pictures is that your trees look good and strong, but as veteran orange trees in your garden they also look like in the past they might have suffered from an unstable water regime. Second, I have no idea how many hours of direct sun light they get (??) but It seems, from looking at the surroundings that the trees are growing in a half shaded area. It's hard to tell from the picture, and I don't know at what time of day the picture was taken, so I think the best thing to do is give you specific pruning instructions for each of your trees. And please, send me the 'after' pictures as well so I can follow their growth process.
Choose your pruning method - See the picture I have marked below. If you wish to get strong, vigorous new growth and a rich yield of fruit you should follow the red line. It will give you an indication of the height I recommend this orange trees should be pruned at. Don't look for the exact point because it's not an exact science, and you will get the same results an inch higher or lower. (But do note the cutting angle, which I have also marked.)
I can see your tree has some great new flowering growth. This will turn into fruit next winter - Enjoy.
As for the green circles, I'll get to those in a second.
Please note - Pruning around the point of the red mark will encourage new growth along that specific stem, which means it will grow right in front of the window.
Now you need to decide if that's what you actually want.
If it were me, I would prune with the aim of getting new growth, a healthier tree, fruits at a height that I can reach out my hand and pick, and a balanced tree structure.
But, if the window is an issue and you don't want to block the sunlight streaming into that room, prune only to remove the dead and dried branches - also marked. Which is fine too. Except for the down side of a tall tree, which is that it can't give too many fruits (taller trees can't deliver sufficient energy to such height for the production of many fruit). So, back to the original question - what do you want from your tree?
One last thing - if you do decide to prune close to the window, please make sure to start by cutting the green circles I marked - for safety reasons, please don't ever prune a whole cluster in one piece, it can be dangerous. And safety my friend, is above all.
Actually, this one is the last thing (I promise) - removing the main branch, which is close to the widow, at this time will definitely give you new growth, I'm just not sure you'll get new bloom immediately. You will probably get some, but if not, don't worry... it will all come out next season. In the meanwhile you'll have beautiful new leaves and a healthy looking tree.
Now see the image below:
Same again, there's no window this time, but generally speaking you want the tree to produce new growth, you want to encourage new thick leaves to grow so the tree looks and feels like a real Orange tree in an orchard.
The green line represent the general shape of the canopy that you want to grow over the next 2 months. It shows the place and height that you should prune at.
The red lines represent branches that are growing in odd directions, which is fine, but if you're going to cut, make the most of it - cutting a little bit off those branches will give you the same results I mentioned above.
1 and 2 - I would advise you to prune one or two branches first, see how the tree responds in the next few weeks. I believe your tree has been waiting for this for a while now, so pruning them slowly, step by step would be the smartest thing to do. If the tree reacts well move onto other branches too. With evergreen citrus trees there is basically no limit as to when or what to prune. Unlike deciduous fruit trees, this is a great advantage to you.
Please note - I have no idea and no way of knowing about other elements effecting the tree, thing like fungus, diseases, etc... I have no way of seeing these things in a picture, so although these are my suggested guidelines keep in mind, pruning may have various effects on the tree - you can't know what might be revealed or encouraged once you prune. The trees look strong and healthy, but you can never know what lies beneath the surface.
And please - check the half shade issue again, if they are growing in half shade, consider pruning some of the branches above that area to allow more sunlight through.
I hope that helps.
Providing general guidelines on 'how to prune' any kind of plant is important, but there are plants, and there is YOUR plant. So despite there being loads of information on this site, I also provide specific and personalized support. If something wasn't clear, or you're not sure of your plant's name, simply send me a picture with your question. Use the form below and I'll get back to you. In the mean time, see what others are asking.