Timely Tree Tips – consider the shape before planting

Trees grow in all different shapes. Consider this when planting a news tree.
Trees grow in all different shapes. Consider this when planting a new tree.

As children, we learn that square pegs don’t fit in round holes and the same principle applies to selecting trees. Trees have a wide variety of canopy shapes and sizes; however, there are some general crown shapes we can identify.

Most conifer trees, for example, are described as having a pyramidal shape—think Christmas trees! Pin oak, linden and Turkish filbert are deciduous trees also known for their pyramidal shape when young; as older trees, their canopies become broader and more rounded at the top.

Here are some other general canopy/crown shapes, with familiar trees to illustrate them:

  • Rounded: Trees with this crown shape have a rounded look resembling a ball or a gum drop. Many crabapple trees exhibit this shape. American hornbeam and hedge maple are other great examples.
  • Upright Oval:Similar to rounded crowns, trees with oval-shaped canopies have shorter side branching which gives a more oval silhouette. Birch, southern magnolia, and white ash tend to have oval-shaped crowns.
  • Columnar: These trees have upright canopies with relatively short side branches of uniform length, making the tree tall and narrow, like a column. Columnar trees have become very popular for narrow planting areas and many species are now available in columnar forms. Armstrong maple is one of the most popular columnar trees available.
  • V or Vase: Elms and zelkovas are the most common trees with upright V-shaped crowns. A vase-shaped crown is made up of limbs that spread upwards and outwards from their point of attachment to the trunk, like a V.
  • Weeping: The weeping willow has captured our hearts and minds thanks to its unique growth habit. So compelling is this form that horticulturalists have developed weeping cultivars of tree species that rarely, if ever, would develop a weeping habit in nature. These days there are weeping cherries, birches, katsuratrees, and even weeping pines, hemlocks and spruces.
  • Spreading: Spreading crowns are typically much wider than tall. This crown shape is far more common among shorter, often multi-stemmed trees. Our native vine maple, as well as many Japanese maple cultivars and many dogwood species have spreading crowns.
  • Free Form: Trees lacking a symmetrical shape like those listed above are often referred to as having ‘irregular’ crowns. This term implies there is something wrong or undesirable about the tree, but in fact, there are some really cool trees with, shall we say, ‘free form’ crown shapes: sourwood, Kentucky coffeetree, and American smoketree are noteworthy trees in this category.

When selecting a tree to plant, imagine the size and shape of the mature tree crown and make sure it will function in the space you have. Keep in mind that tree canopies often change shape naturally as they mature. Trees with weeping or spreading forms make poor street trees because they don’t allow for good traffic and sign clearance, whereas columnar, oval, or vase-shaped trees may be more appropriate for the roadside environment.

Let’s all be planting the right (shaped) trees in the right (shaped) places!

Here are more resources to learn about tree canopy shapes:

The University of Tennessee: A palette of tree canopy forms

Better Homes and Gardens: Selecting trees by shape

The Arbor Day Foundation: The right tree in the right place shape guide