Experts and BHG readers answer.
"Have you had any late frosts? If so, that could kill the flowerbuds. The fact that this has happened several years in a row, though, indicates something else. You say light shade and crabapples are a sun-loving species, so depending on just how light the shade is, that could affect flower production. You might also do a soil test to make sure there is no deficiency of phosphorous, which would also affect flowering.
Luke Miller, editor
Garden Ideas & Outdoor Living magazine