Sun and Shade
Most hydrangeas prefer morning sun and afternoon shade, and don’t deal well with hot climates. Coastal climates are ideal, as are cool summer areas. Both too much heat and too little sun can contribute to poor performance for old fashioned hydrangeas. PeeGee hydrangeas deal much better with heat. Oak leaf hydrangeas are perfect for partial shade areas. No hydrangea will bloom in deep shade.
Water and Fertilizer
Hydrangeas prefer to be evenly moist, and love a fertile spoil. That having been said, when using commercial fertilizers, it’s often advised to use half strength liquid fertilizer so you don’t stimulate too much leaf growth at the expense of the flowers.
Most (except re-bloomers) bloom on old wood, so severe pruning is not necessary. Prune away dead wood each spring, and dead head the flowers that are past their prime to promote the most flowers on each bush. PeeGee and Annabelle hydrangeas are more tolerant.
Hydrangeas prefer soil rich in organic matter. You may have heard that you can change the color of a hydrangeas blooms based on soil composition. It’s true that the pink and blue varieties are influenced by the soil ph. You can change a pink hydrangea to blue by adding aluminum sulfate to the soil to make it more acidic. It is pretty difficult to change a blue hydrangea to pink…
The biggest problems hydrangea gardeners have is lack of bloom… This is usually caused by one of three things… a late freeze, using a variety that is not intended for your climate, or pruning too much of the old wood away.