Q. My lemons form and ripen on the tree but when I cut them open they are dry and brown to black inside and have virtually no juice?
The tree is under stress and in order to get it through hot seasons it pulls back the sap or juice from the lemon fruits to make sure that the tree survives. In order to help the tree avoid such stresses regular watering is important through the summer months. I always like to see a generous layer of mulch out to the drip line (the outer edges of the foliage). Go for 50 to 75 mm thick, composted mulch. When the tree is in active growth, fertilising with Blood and Bone is worth doing to support the growth.
A quick fix is to cut, using secateurs; full sized fruits from the tree while these are still green. Ideally, leave a stub of stem on the fruit as this aids long life. Wrap the lemons in newspaper and store indoors in a dry dark place. The lemons will colour up yellow over a couple of weeks and store for a few months. The idea behind the wrapping is to prevent skin-to-skin contact, which often leads to a blue mould developing which, then rots off two or more fruit, sometimes the whole stored crop.