In the next few weeks we’ll be seeing the growth forms of deciduous trees outlined against the autumn sky, sans foliage. This is the ideal time to assess and appreciate the shapes of our trees, whether they are rounded, oval, pyramidal or fastigiate (columnar).
No matter the landscape problem that needs to be solved, there is a tree form that will work. All that is required is for the gardener to do their homework to first figure out what type of space is available for the tree, and then to determine which trees will be appropriate.
Demand for columnar trees is increasing, as lot sizes become smaller and houses are built closer together. Homeowners want privacy from their neighbours, shade from the afternoon sun and trees to appreciate for form, foliage and flowers. It takes a certain type of tree to satisfy all of these requirements on today’s typically smaller lot.
Fences and evergreen hedges will only screen out so much, particularly if there are second-storey decks or sitting areas that need some privacy. At the garden centre we talk to many customers who are looking for trees that can grow fairly tall, while not growing so wide that they cross over property lines or block driveways, sidewalks or sight lines.
Here are some good tree choices where narrow is the required tree form.
Acer platanoides ‘Columnare’ Columnar Norway Maple-slow growing, with a broad, columnar form. Deep green foliage turning a bright golden yellow in fall. Grows 15m tall but just 6 m wide.
Acer rubrum ‘Armstrong’ Armstrong Red Maple-fast growing, with lovely silver-grey bark and bright orange/red fall colour. Grows 16 m tall and 5 m wide. ‘Bowhall’ is another narrow cultivar of the Red Maple with good red fall colour.
Carpinus betulus ‘Fastigiata’ Pyramidal Hornbeam-A dense growth habit and very uniform habit make this a popular tree. Dark green foliage with a nice texture. Becomes more rounded as it ages, but strongly columnar for the first decade of growth. Matures at 10 m tall and up to 8 m wide. ‘Frans Fontaine’ has a similar appearance, but only grows 5 m wide at maturity.
Fagus sylvatica ‘Dawyck’ Fastigiate Beech-very narrow form and deep green foliage make this a striking tree. There is also a golden-leaved form. Matures at 15 m high and 5 m wide.
Gingko biloba ‘Golden Colonnade’-Gingkoes are popular street trees, and this form has a narrowly oval growth habit, perfect for smaller spaces. It grows 13 m tall and 7 m wide. ‘Princeton Sentry’ has a very stiff, upright form, growing only to 5 m wide.
Magnolia ‘Galaxy’-a great choice for those wanting a tree with spring flowers. The strong central leader gives this magnolia a very pyramidal form, growing 10 m tall but just five metres wide. It has reddish-purple flowers in spring. ‘Moonglow’ features fragrant lemon-scented blooms in late spring on an upright growing tree that is similar in size to ‘Galaxy.’
Populus ‘Tower’-Poplars must be used with discretion, as they have issues relating to their weak wood and aggressive root systems. Still, if you have adequate space for their roots to roam the strongly upright form of the Tower Poplar or others such as ‘Prairie Sky’ can make for a very useful screening plant. These two cultivars will mature at 12 m tall and 3 m wide.
Populus tremula erecta (Swedish Columnar Aspen)-This variety is better suited to “normal” home lots. Growing 12 m high and just 2 m wide, it has a very tight columnar habit, with glossy green foliage and striking yellow fall colour. Nice if only for watching the shimmering leaves in the wind.
Quercus robur ‘Fastigiata’ Skyrocket English Oak-known for its uniformly narrow habit, this popular street tree grows 12 m high and 4 m wide. A similar tree is a cross between this tree and Quercus bicolor. Called ‘Regal Prince’ it is a vigorous grower that becomes more oval as it matures.
Sorbus acuparia ‘Cardinal Royal’ – This form of Mountain Ash is one of several with an upright growth habit. It features very show bright red fruit and a symmetrical, tidy habit. It grows 10 m tall and 6 m wide. ‘Rossica’ has red fruit as well and is slightly smaller at maturity than ‘Cardinal Royal.’ Sorbus have beautiful orange, red and yellow fall colour.