Ornamental pears used to be called Bradford pears. This was a bit of a misnomer as ‘Bradford’ was a specific variety. Ornamental pears were called Bradfords because this was practically the only variety that people planted. Therefore, if you bought an ornamental pear a number of years ago, it was likely a Bradford. All was well and good until people noticed that Bradfords would fall apart after a number of years due to a weak branching structure. Therefore, nurseries started selling “improved” ornamental pears that were not Bradfords such as ‘Aristocrat’, ‘Capital’, ‘Chanticleer’ and various other varieties. These varieties had a much better branching structure.
Here is the key. Pears usually require cross-pollination in order to fruit. In other words, you must have two different varieties of pear before fruit forms. When all we had were Bradfords, we had no fruit due to a lack of cross-pollination. Now that we have such a mixture of varieties, we will get fruit as long as two different varieties of ornamental pears are close enough that bees can work between them.
This formation of fruit can also lead to a second problem. Volunteer trees can come up from the seed contained in the fruit. Therefore, you may see ornamental pears come up in areas where no one planted them.
There isn’t much homeowners can do about these trees producing fruit. Just be careful to plant in an area so that, if fruit forms, it will not be a nuisance. (Ward Upham)