Citrus australasica, finger lime, seems to me to be pretty easy to grow.
Mine is now about 5 years old, and has been flowering and bearing fruit for the last three years. I would guess that it is a grafted specimen, although it doesn’t say that on the label.
My variety is ‘Crystal’: Green skin, green ‘caviar’ – very fresh, very juicy. The grower is Gourmetlimes.com.au.
I have it planted under a large mango tree, north facing, but due to shade from other plants around it, it probably only gets half sun at best. Being a rainforest plant, it seems to be a good spot for it.
I don’t feed it and only water it when I remember, usually when I notice the small flowers on it in spring and think I should help it to set fruit!
In summer, I may see stink bugs which cause dieback of some new growth, but not as many as I get on my orange tree nearby.
I generally only prune to keep it in control and at about chest high. It is VERY prickly and I always wear gloves when working nearby.
Collection of finger limes: This season, I got about 30 fruit off it and have been having them on my breakfast cereal and puddings daily. They are also good on fish and in salads.
For those who also have this plant, the fruit are ripe when they just come off the plant easily when you pull lightly and I read that they do not ripen off the tree. You can freeze them if you have a huge crop.