Lemon tree fruit won't ripen - Garden

Hello, Colm -

This article from GardeningKnowHow.com may prove instructive:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-not-fruiting.htm

Best wishes.

Magnesium deficiency more than likely

some times fruits are grown too fast and what happens it takes longer for it to ripen so it depends where you buy you'r fruits and when it ripens it has very little sugar.now if you buy from farmers market the chances of getting a good fruit are better.so if you bough the honeydew at farmers market just leave it in a cool place in the house for a 1-2 this way the honeydew sugar gets sweeter after you can refrigerate and then eat.aside from the honeydew...how to make good lemonade.-- good lemonade taste better without the sourness to eliminate the sour of the lemon you take one dozen lemons and set them outside in the sun until the skin of lemon is dry you turn the lemons over once every 4 days do this for 2 months,and when you make the lemonade you will have a mile lemonade.D,R,CLAUDIO

Treat your lemon tree like an Olympic athlete - feed well and regularly, hydrate well and keep diseases at bay. Trim out dead wood and if leaves are yellow, mix some Epsom salts into your citrus fertiliser. When you mulch, stay away from the base of the trunk - citrus are prone to collar rot.

To treat, remove all infected leaves and dropped fruit from the ground. Prune the lower branches from the tree, those that are more than 2 feet from the ground. Then spray with a fungicide such as Agri-Fos orCaptan. Botrytis fungus - Botrytis rot is yet anotherfungal infection which may afflict lemon trees.10 Jan 2016

Lemon Tree Problems: Treating Common Lemon Tree Diseases

https://www.gardeningknowhow.com/edible/.../lemons/common-lemon-tree-diseases.ht.. What is the Treatment for diseases of lemon trees Google Search

Lemon trees are extremely sensitive to over watering, only thing you can do is make sure you have good drainage. Dig channels at low points to make sure ground water moves away. Just a small point, you posted your question on the Cars & Trucks section, you may be missing some better solutions by posting here, however, I've raised a few lemon trees in Spain and in my front room in London so I have a little experience in this area.
Good luck

Ethylene
Not only in mangoes does it help with ripening but in most fruits this is the case

loquat

It could take up to 7 years in some climates to fruit. It's self pollenating but likes a Ph level of 6 to 7.5. Get a soil Ph tester & check your soils Ph levels and maybe fertilize it with a fruit tree fertilizer. That's the best I can tell ya. Hope it helps