Lack of blossom....

Grajean

Several apple trees and a pear tree do not have any blossom this year. Last year we had amazing fruit crops off them. Could the cold weather have caused the problem or are the trees just "resting"?

hogweed

Perhaps the blossom is just a bit late?

Fairygirl

They do sometimes have a lean year following a highly productive one. If you have none at all, and only foliage appearing, that may be the reason. Give them plenty of tlc and hopefully they will recover well for next year. 

Mine are only just starting to sprout although that's normal here. It also may be as hogweed suggests, and they will suddenly spring to life. 

BobTheGardener

Another possibility is that something ate the flower buds over winter.  Typically, that could be bullfinches, woodpigeons or squirrels.  If you look at the tree next winter, you will be able to see the fatter buds which will carry the flowers.  If you notice these disappearing as the weeks go by, you'll know why.
As Fairy says, it could just be that they are having a year off.  This "biennial bearing" can become a pattern but it would be unusual for all of your trees to do it but possible if they all cropped very heavily followed by poor weather (eg drought or little sun) as they wouldn't then be able to take in enough energy to form the new flower buds.