Generally speaking, hydrangeas prefer a location that receives partial shade or filtered sun. Most like shade in the hot afternoons, but some varieties like more sun than others.
Purchase your hydrangeas from the gardening section, and ensure they don’t have brown roots, as this can indicate health issues. The best time to plant them is in late spring.
To boost hydrangea blooms, use well-drained, organically rich soil. Alkaline, acidic, and neutral soils can produce pink, blue, and purple flowers, respectively.
As for the fertilizers, high phosphorus ones will boost blooms, while nitrogen-rich ones will promote leaf and stem growth. If the soil is nutrient-rich, avoid over-fertilizing.
Hydrangeas need plenty of water. The best method is to water deeply enough to reach the roots, ensuring you do so at the right time of day and in the right spot.
Water on leaves and blooms can harness the sun and cause burns, so aim to water your hydrangeas early in the morning. Avoid overhead watering, as it can cause fungal diseases.
You should prune old wood hydrangeas immediately after they bloom. This allows the plant to work on growth that will become old wood for the next season.
New wood varieties develop buds on the current season's growth and need pruning in late winter or early spring. Knowing the type of hydrangea you have is the key to proper pruning.