Training Shrubs to Single-Stem Tree Form
Looking to add a distinctive feature to your yard? Try training shrubs into a long, branchless central stem topped with a full head of foliage. With quality plants, the right technique and patience, you can transform your favourite shrubs into dynamic tree silhouettes. Here’s how.
Start with a high-quality shrub in a one or two gallon pot and plant as you would any shrub.
Examine the shrub and select the largest, healthiest stem. This will become the ‘trunk’ of your tree-form shrub. Prune off most of the other stems, leaving some extra branches untouched for the moment. The extra foliage of these branches will give the plant the energy it needs to grow.
Maintain the tree form by pruning off new side shoots so that all of the plant’s energy goes into the remaining stem.
Stake and rod the stem to keep it upright. The rod and stakes should remain in place until the selected stem is able to support the weight of the plant.
Once the shrub reaches the desired height (1.2 m of clear stem is a good guideline), clip the top to force buds out, and remove any buds on the stem. This is also the time to remove those extra branches you left on the stem for plant growth. Treat like a normal shrub to produce a nice round head.
The shrub will continue to produce shoots in unwanted areas. Remove these shoots to maintain the tree form.
Make sure your expectations are realistic—training will not transform a 2-m tall shrub
into a 4-m tall tree, though your shrub may grow a little taller than usual because the
plant’s energy has been redirected to a single, central stem.
You can train almost any shrub, but here are a few suggestions to get you started.
Multi-Stemmed Tree Forms
Many large shrubs can be trained to multi-stemmed tree forms of three, five or seven
stems. Russian olive and amur maple look beautiful when trained to these forms.
Buying Tree-Form Shrubs
If you like the look but don’t feel like doing the work, you can buy mature shrubs in tree
form. Some of these shrubs are trained to tree form (dogwood, potentilla, ninebark, hydrangea), while others are created by grafting a shrub such as lilac or caragana to a
compatible rootstock. Note, however, that grafted tree-form shrubs are generally easier
to maintain than trained tree-form shrubs, as the rootstocks are chosen both for height
and their tendency to avoid creating side shoots. Grafted tree form shrubs come in a
variety of heights. In some cases, the central stem may be a metre tall, in others only
half that. It all depends on what the grower has chosen.