Many different species and cultivated varieties of hydrangeas exist, but a few are best adapted for growing in containers. Annabelle hydrangeas (Hydrangea arborescens), oak leaf hydrangeas (H. quercifolia), big-leaf, French or florist hydrangeas or hortensias (H. macrophylla) and PG or PeeGee's hydrangeas (H. paniculata) are the best types for container growing. Hydrangeas are beloved for their showy, large flowers that typically bloom in shades of white or pink from summer through fall. Container-grown hydrangeas usually stay compact and grow 3 to 4 feet tall and wide.
Pot your hydrangeas in a container that's about 1 1/2 times the diameter of the plant's roots and that has drainage holes in the bottom. Plant the hydrangea at the same depth as it was planted in the nursery container and in a very well-draining, bark-based potting mix.
Place your container-grown hydrangeas in full, direct to partial sunlight, such as beside a south-, east- or west-facing window. Hydrangeas can grow well in a spot that receives full sunlight in the morning and some shade in the afternoon.
Water your potted hydrangeas evenly and thoroughly when the top layer of potting soil begins to feel dry to the touch. Keep the potting soil moderately moistened, but not waterlogged or saturated. When you water the hydrangeas, pour water into the pot until it begins to drain from the bottom.
Feed your hydrangeas once each year in spring with a controlled-release fertilizer made for flowering plants and shrubs. Follow the application and dosage instructions on the fertilizer label.
Prune your potted hydrangeas to shape them and thin out crowded growth while they're actively growing. Cut away all stems that have already produced flowers. Perform heavier pruning in early spring when the leaf buds are just beginning to form, removing all dead, damaged, diseased and crossing branches.