Types

• Most hydrangeas have a central root ball beneath the soil that sends up multiple branches to form a shrub. But paniculata hydrangea plants, also known as pee gee hydrangeas, have a central stem. You can prune this stem into a tree form by removing the lowest limbs.
  
  

Features

• Paniculata hydrangeas may reach a height of 20 feet. These shrubs take well to pruning, which makes cutting back lower limbs a simple process.
  
  

Significance

• Another type of hydrangea that can form a tree shape is the climbing hydrangea. Climbing hydrangeas cannot climb unsupported, but if supported by a trellis can form a tree shape. Climbing hydrangeas are capable of reaching 60 feet in height.