Q.Why Are My Pear Trees Not Bearing Fruit?
I have several trees in my orchard that are now 12 years old. The tree is growing great, but the only fruit is ever gets is a small round green bulb about the size of a cherry. There are lots of them on the trees, but nothing edible. The trees get full sun, plenty of water, I fertilize every year, but no fruit. The trees were marked Seckle Pear when I bought them, but I am not sure that is what they are. Should have had some fruit by now.

Certified GKH Gardening Expert
Unfortunately, your photos did not come through. From the sound of it, though, fertilizer ratios may be off.
Lack of fruit will happen when there is too much nitrogen, and not enough phosphorus and potassium in the soil. Make sure to test the soil before feeding so that you know what, and how much, to add.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/edible/fruits/pear/growing-pear-trees.htm
https://www.gardeningknowhow.com/edible/fruits/pear/fertilizing-a-pear-tree.htm
https://www.gardeningknowhow.com/edible/fruits/pear/pear-tree-pruning.htm