|In past, white hydrangias were cut ground level. This year they were 18|
|Your pruning will depend on what kind of hydrangea you have. If it is Hydrangea arborescens such as "Annabelle" you would routinely cut it off short each year in late winter. If it is a woody hydrangea such as the PeeGee (Hydrangea paniculata) you would also prune it in the late winter, but only if needed to remove broken branches or desired to shape it or to control its overall size.
Hydrangeas can be fertilized in early spring and in early summer with a topdressing of good quality compost and/or a granular all purpose fertilizer such as 10-10-10 per the label instructions. Watering them during dry spells can also be helpful.
With both of these hydrangea types, one common reason for lack of bloom is that they are planted in too much shade. They do require some direct sun to bloom well. The H. arborescens does well in morning sun or very bright dappled light all day, while the H. paniculata can tolerate up to a whole day of sun if the soil is evenly moist.
I hope this helps.