I have a lot of vines. They are several years in the ground and keep shooting growth but no flowers. We do not fertilize and only water moderately one time a week. They are in a northern exposure close to the house. They get the am sun but not the intense southern pm sun.
How Do I Get My Bougainvilleas to Flower
Certified GKH Gardening Expert
If they are getting enough light (which is the most common reasons for plants failing to flower), then it is likely a lack of phosphorus. Plants need phosphorus to flower. Bone meal is a good source of phosphorus (https://www.gardeningknowhow.com/organic/bone-meal-fertilizer.htm).