How to Train a Flowering Shrub into a Distinctive Ornamental Tree

Lime Soda(TM) Hydrangea

Who wouldn’t want an extremely surprising, head-turning small tree covered with massive, fluffy panicles of white flowers in July that change to vivid pink over the next few months? Easy pruning over a season or two can turn an unusual shrub into a tree form that is perfect for small gardens, as well as being distinctive and unique.  

Generally, shrubs have very different growth habits than trees. While both are woody ornamentals, shrubs are lower growing and have multiple stems that sprout from the base of the plant, while trees are typically taller and single-trunked. But Mother Nature is anything but black and white.

Certain tree species commonly have multiple trunks—such as river birch (Betula), cherry laurel (Prunus) or Chinese Elm (Zelkova).  Conversely, some woody plants that normally grow as shrubs can be pruned or “trained” to have only one trunk-- like tree roses, Rose of Sharon, Viburnum or Althea. Even woody vines such as Wisteria can be trained into a tree form, as explained in our popular blog from 2010.  In these cases the distinctions between the landscape forms become blurred.

multi-stemmed shrub

A robust new shrub appealingly named Lime Soda™ Hydrangea is the perfect choice to prune into a dramatic landscape tree for smaller gardens across the country. Hardy from U.S.D.A. Zone 3 to 8, Lime Soda™ Hydrangea from Garden Debut® has mammoth flower heads that open white in July and change to vivid pink in the next couple of months. 

Lime Soda™ Hydrangea: 

is naturally upright

responds well to pruning

has strong, stiff branches

is fast growing

reaches about 10 feet, ideal for a small tree

pruned to single trunk

Step by Step Creative Pruning to achieve a tree form

+ Before you buy, examine young nursery plants and choose one with a strong central leader
+ Eliminate all the branches arising from the crown at ground level except this leader, which will become the tree-form trunk

+ Prune off branches from the lower 1/3 of the remaining leader flush with the trunk, known as “limbing-up”

+ Guide a strong nursery stake down along the main trunk, hammering in securely, then loosely tie the plant to the stake using a soft tie and a figure 8 around both stake and trunk

+ Allow the top 2/3 of foliage to photosynthesize and the plant to establish a good root system during the rest of the year

+ The following season, limb-up another third of the lateral branches from the trunk. Repeat Step 5 for another year or two until the trunk has reached the desired height, perhaps 5 to 7 feet. Remove the stake.

lower branches removed

+ Select about 5 scaffold branches evenly spaced around the trunk that will become the canopy of the tree, and pinch each of those back about 3 inches to encourage lateral branching  

+ Keep the trunk clean with no branches below the canopy. That is all there is to it!

+ Mulch or underplant Lime Soda(TM) Hydrangea with Snow N Summer Asian Jasmine in warmer climates, or with annuals or Lenten roses for year round appeal.