I recently received the following question from Julee on my Ask Me a Question page: “I’m wondering what kind of large shrubs may be pruned to have a more tree-like appearance, and tolerate only dappled sunlight….” She wants a tree like shrub to soften the vertical line on a corner of her house. It needs to be hardy to zone 4 and not get too big.
Given her requirements here are my recommendations for some tree like shrubs.
Horizontal branching tree like shrub: Pagoda dogwood (Cornus alternifolia)
This is one of the best small trees / large shrubs to use to help break up the vertical lines of a house. Pagoda dogwood has a horizontal branch pattern that is really attractive in all seasons. It really helps to show off its’ flat white flowers in the spring.
The plant also gets a purple fruit that the birds will enjoy. They tolerate shade and are hardy to zone 3. The species grows to 15 to 25’ high. This is probably the ideal shrub for Julee; however it may grow a bit too large.
If she could find the cultivar ‘Argentea’ which has variegated leaves and only grows to about 15 feet tall, I would recommend this plant as perhaps her best choice.
Blackhaw viburnum (Viburnum prunifolium)
Blackhaw viburnum has hawthorn like branching and reaches 10-15 feet. It is hardy in zone 3-9. Dark green leaves turn a purple-red in autumn. White, flat topped, flowers appear in May. It has bluish-black fruit that will attract birds. Its’ height if not pruned reaches about 12-15′. It grows fine in sun or shade in any soil type, even dry soils. It is considered very drought tolerant. This would be a good choice that would not require a lot of pruning.
American Cranberry bush viburnum (Viburnum trilobum)
My absolute favorite tree like shrub to prune into tree like forms once the branches get some thickness. This is a plant that requires annual pruning to get the most out of. I had to include because it has so much potential, however it does require a lot of care.
It grows to about 12 feet high, but can be kept half that tall. It has nice bright red fruit that holds well into winter before the birds get it. It has a nice red fall color and can develop nice winter branching.
Catawba Rhododendron (Rhododendron catawbiense)
As far as evergreens, Rhododendrons are probably some of the best of the shrubs for shade. That is if your soil is right. If your soil is neutral or slightly alkaline, it will require amending. Rhododendrons not only thrive in shade but also seem to go with with it. These shade-loving shrubs are loved for their colorful flowers and interesting, evergreen foliage.
One of the larger growing Rhododendrons that can (eventually) be pruned into a tree is the Catawba Rhododendron. This plant is hardy to zone 4 and can grow to about 10 feet in height (or more). It will certainly require a well amended soil and some periodic watering during dry periods.
While there are certainly other shrubs that can be pruned into tree forms. These are some of my favorites for a zone 4 shaded environment.