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All, Summer

Gardening With Perennials

August 31, 2021

Gardening With Perennials

Gardening With Perennials

Gardeners love perennial flowers for their infinite variety, their hardiness, and the ease with which you can propagate more. They return each year so they are also cost efficient.

Learn how to select what's right for your outdoor living space.


Unlike annuals that bloom all summer, perennials have a limited flowering time.

  • The Tree Peony blooms for only a few days and the Astilbe a few weeks.
  • The bloom could last several months which is the case for the Pincushion Flower or Thread-leaved Coreopsis.
  • The trick is to have your perennials bloom specifically when you want them to whether it’s late winter with Hellebores, spring with Columbines and Rock Cress, mid-summer with Daylilies and Summer Phlox, or fall with Bugbane, Japanese Anemones, and Chrysanthemums.
  • When your perennial isn’t flowering, you may want to rely on attractive foliage colours like the green and white leaves of Jacob’s Ladder, Heuchera, and Variegated Obedient Plant.

Perennial (Herbaceous) Borders

  • The tradition of perennial borders with long gardens that are brimming with perennials that are sequenced to bloom from spring through late fall, tiered from short at the front to tall at the back are hardly practical on our smaller properties.
  • We can adapt the idea to grow perennials along a sidewall of the house or a fence in the back garden. Instead of planting in groups of 3 of the same plant to create a large “drift” effect, just establish one plant. The challenge is to have something blooming from April to November.

For the most part, perennials are fairly adaptable.

  • Perennials do best in well-drained soil that’s had Parkwood®3 in 1 Planting Mix, peat moss, manure, or compost worked into the top 20 cm (8”) before planting.
  • Add granular Garden Special or Bonemeal, at the recommended rate to the amended soil.
  • Perennials can be purchased as starter plants in small pots in the spring or various sized pots ranging from 1, 2, 3 and 5-gallon sizes. When easing the plant out of its container, check to see if its root bound. If this is the case, gently loosen the moistened root ball with your fingers, place in the planting hole, and firm soil around it.
  • Dilute Parkwood®Transplanter 5-15-5 as directed and soak the area. Keep your perennials well watered the first year to get them established.
  • Before winter sets in, cut all your perennials back close to the ground unless you wish to leave seed pods for winter interest or as a food supply for birds.
  • Do not prune back Ornamental Grasses, Lavender, and Russian Sage in fall. They are best trimmed back in early spring.
  • Water your perennials deeply before the ground freezes up in late autumn and mulch any plants that you feel may be borderline hardy or might be exposed to a lot of cold, winter wind.
  • Once established, feed your perennials in April/May and again in July such as Bonemeal or Fafard Natural Perennial Food. Granular fertilizers slowly release nutrients over a two month period while water-soluble fertilizer needs to be applied more frequently.
  • Deadhead spent flowers regularly except when you’re seed collecting. Always keep the garden tidy so insects can’t hide under decaying leaves.

Your first consideration will be the light conditions that vary throughout your property.

  • For heavy shade, Ferns and Hostas will flourish
  • For sunny conditions (6 hours per day) the Russian Sage and Purple Coneflower will do beautifully.

The majority of perennials grow well in partial shade (especially in eastern exposures) when they are not in the hot afternoon heat.


Perennials fall into 3 distinct height categories (short, medium, and tall).

  • The short varieties are frequently used in rock gardens, as ground covers, or as edging plants. One of the most versatile, low-growing perennials for sun is Dragons Blood Sedum
  • Medium-sized perennials include such favourites as Peonies, Lupines, and Shasta Daisies.
  • Tall varieties like Mullein, Joe-Pye Weed, as well as various Ornamental Grasses are impressive and add bold structure to any garden. Some tall perennials like Delphiniums require staking so maintenance should be considered.

Perennials come in every colour imaginable.

  • Perennial Salvia, Delphinium, and Veronica come in many tints and shades of blue
  • Sizzle and Spice Coreopsis Series have brilliant red flowers
  • Monkshood and several varieties of Aster represent the colour purple.
  • Butterfly Weed is a native species with a vibrant orange flower in the late summer, and attracts pollinators.
  • Moonbeam Coreopsis is lemon yellow
  • Rudbeckia varies from yellow to gold
  • White can be used in any grouping to cool the “sizzling” colours, to blend with softer tints, or by itself as a pure white garden.

Perennials can easily be planted with shrubs, evergreens, smaller shrub roses, bulbs, and annuals. It’s important to keep proportion in mind so a perennial isn’t lost against a large neighbour. In foundation plantings, where the overall form of the plant and its foliage are as significant as its flowers, remember Bergenia, Siberian Iris, Autumn Joy and Brilliant Sedum, Hostas, Lady’s Mantle, Perennial Cranesbill, and small to medium size Ornamental Grasses.


Your perennials may need to be divided if they are flowering less, the flowers become smaller, or do not develop fully.

  • Divide the plant in the spring before it can fully leaf out.
  • With a sharp spade split or quarter the clump. Leave one portion in the ground and transplant the other half (or three quarters) to a new location.
  • Use Parkwood®Transplanter to get your newly planted divisions off to a good start. There are two perennials that should not be split in the spring. The Herbaceous Peony should be divided or moved in mid to late September while the Bearded Iris prefers to be divided in mid to late summer.
  • If you’ve never gardened with perennials or are just starting, have no worries. Perennials are easily moved when colours clash, the tall one is in front of the short one, or you have too many daisy flower forms blooming side by side.