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Garden Geometry 101

Landscape Design, Perennials, Trees & Shrubs

When it comes to choosing plants for a garden, many factors come into play. Too often than not these factors and choices become over whelming. When looking at any type of design whether it be art work or interior decorating, colour is the first factor that we tend to notice. The second, following closely behind, is shape. Let’s go wayyy back to our elementary days and take a closer look at shapes and how they can lend a helping hand in deciding what goes where in the garden.

Globes and Circles

In the garden, drama is achieved in many ways.  Utilizing spherical plant material is an easy and effective way to do just that.  Flowers that are circular in shape provide dense bursts of colour that bring a garden bed to life! This effect is not just for flowers.  Many shrubs and even trees are available in these forms. 

The perennial bulb ‘Globemaster’ Allium has dense flower heads that appear as floating purple balloons in the garden.  Planting groupings of these throughout a landscape will playfully lead the eye through the space creating unity.

Images (left to right): Allium, Globeflower

Other globes and spheres to consider


  • Globeflower (Trollius)

  • All members of the onion family (chives, garlic and alliums)                 

  • Peonies (and nothing beats the fragrance!)

  • Beebalm (Monarda-another fragrant fav!)

  • Agapanthus (A gorgeous tropical plant that is worth wintering in the house)


  • Hydrangeas (Check out all the newbies for all season long colour!)

  • European Snowball (Viburnum opulus ‘Roseum’)

  • Globe Blue Spruce (Great evergreen for a pop of colour all year long)


A close relative of the globe is called an umbel.  Umbels are like half-spheres.  In the garden they create the same bold energy as the globe but in a slightly different form.  These can be used in conjunction with globes or intersperse them as part of your consecutive flowering sequence to add more texture and interest.

Images (left to right): Masterwort, Yarrow

Worthy Umbels


  • Pincushion Flower (Scabiosa)

  • Yarrow (Achillea-great drought tolerance)

  • Joe Pye Weed (eupatorium-butterflies love these big beauty!)

  • Angelica (Huge plant that with multiple medicinal qualities)

  • Masterwort (Astrantia-nice plant for partial shade)


  • Elder (Many awesome foliage varieties to choose from)

  • Spirea (A classic and pretty shrub-very adaptable)

  • Highbush Cranberry (Viburnum trilobum-the birds will love you!)

  • Dogwood (Sericea or Alba-great for tough locations)

Spikes and Spears

Spike-like flower forms loosely translate into triangles.  These shapes are used more for stability in the garden offering a solid linear foundation.  Plant these is groups of at least 3 to provide backdrops or large swaths of colour.

Images (left to right): Liatrus, Ligularia

Must have Spikes and Spears


  • Liatris (bold spikes that make butterflies swoon)

  • Delphinum (great at the back of the garden for adding height)

  • Ligularia (add some major impact to your shady sites!)

  • Salvia (a personal favourite for long lasting colour) 

  • Veronica (another long bloomer)

  • Reed Grass (Calamagrostis)

  • Switch Grass (Panicum-striking fall colour)

  • Red Baron Grass (Imperata-one of the only red-leaf perennial grasses)


  • False Indigo (Amorpha fruticosa-unique Ontario native)

  • Summersweet (Clethra-bonus* it’s fragrant!)

  • Emerald Cedar (Thuja-great for evergreen screening)

  • Columnar Blue Spruce (Picea pungens ‘Fastigiata’-awesome evergreen for tight spaces)


Flare and exuberance are what comes to mind with plants of this form.  Reminiscent of a triumphant water fountain or burst of a symbol’s crash.  This shape is a standalone to be used in moderation to provide a focal point or to transition between other shapes. 

Images (left to right): Maiden Grass, Jelena Witch Hazel

Vases to watch out for:


  • Ferns (must have for the shady spots)

  • Spiderwort (Tradescantia-unique flowers on grass-like foliage)

  • Crocrosmia (bold colours!)

  • Moor Grass (Molinia)

  • Maiden Grass (Miscanthus gracillimus)


  • ‘Jelena’ Witch hazel (Hamamelis x intermedia 'Jelena'-awesome fall colour)        

  • Bridalwreath Spirea (Spiraea x vanhouttei-stunning display of white flowers in June)

Remember that these same principles can be applied when designing for large properties.  Instead of focusing on flower forms, take a closer look at the entire shape of the plant (ala shrubs and trees).  This will achieve the same concepts but in a scale that suits the size of the property.

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