I have 6 citrus plants bought from the nursery and it has been in ground for 5 years in full sun and still no flowers nor fruit. How can I get it to fruit
Citrus often take five years or more to flower and fruit. Some take more than others.
Overferilizaion with nitrogen can cause some citrus to just be vegetative and not flower. This can result from you giving the plants too much, or them getting it from your near-by lawn care. You can avoid the lawn-care situation by not applying lawn fertilizer in the trees' root zone.
Underfertilizing can also result in no flowers. Make sure you are providing adequate fertilizer for your trees. You usually see other symptoms if you have a deficiency, but it may be 'marginal' and all you see is lack of flowering. Go to your Extension Office or Website and see what they recommend locally.
Nearly any other stress can cause this too. Too cold is often an issue, but you usually see other damage. Same with too much or too little water. Hopefully you planted correctly and don't have an issue there (look up how to plant a citrus tree to see if you did it correctly and it still looks like it should). Your local Extension office will often have this info as well.