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Fri, 07/20/2012 - 10:22 — Sarah Martinez
From flowering shrub to ornamental tree
A step-by-step approach
Today’s guest blogger is Geri Laufer, a lifelong gardener, horticulturist, herb lover, cook, garden writer, author and plant photographer. You can follow her horticulture adventures on her blog, Plant Preview.
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 this popular article from 2010. In these cases the distinctions between the landscape forms become blurred.
Here’s a step-by-step guide to 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 this step for another year or two until the trunk has reached the desired height, perhaps 5 to 7 feet. Remove the stake.
- 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!
To add more appeal, consider mulching or underplanting your new tree with hardy groundcovers—like Snow N Summer Asian Jasmine—in warmer climates, or with annuals or Lenten Roses for year round appeal.
Multi-stemmed shrub (illustration)
Pruned to single trunk
Lower branches removed