10 Neat Things About Perennials
by Dorothy Dobbie
by Dorothy Dobbie

The Local Gardener magazines, Ontario Gardener, Manitoba Gardener and Alberta Gardener, are published by Pegasus Publications Inc.

Drawing on her 30 years' experience as a senior executive in the magazine publishing industry, Dorothy launched Manitoba Gardener in 1998, initially running the business out of her home. Two years later, Dorothy's daughter Shauna, living in Ontario, jumped into the fray with Ontario Gardener. And two years after that, they started Alberta Gardener. Visit us at and register for our "Ten Neat things" newsletter. Watch Shaw TV for garden tips and Listen to CJOB for the Gardener Sundays at 9:08

April 13, 2014

1. Takes a licking, but goes on ticking.

Perennials are plants that come back from the same root year after year. In cold climates, the herbaceous types die back to the ground, but the roots stay warm and snug and vibrant under the earth, where stored sugars keep them alive until it is time to send up springtime shoots of new growth. Some "evergreen" types of perennials (such as heuchera and bergenia) may keep their leaves over winter, even under the snow.

2. How long is long?

The term perennial refers to plants that live longer than two years, but some perennials don't live much longer. Delphinium is a short lived perennial that will often self-sow making it appear that they are long-lived. Some live as little as three years. Other short-lived perennials include columbines, dianthus and Shasta daisy to name just a few.

3. Long livers.

Many perennials have much longer lives - peonies and clematis can bloom happily for 80 years, and more if they are divided. Hostas, daylilies, pulmonaria and balloon flowers are all long livers.

4. Making cutbacks.

Should you cut your perennials back in fall or spring? They won't die if you are a compulsively tidy gardener, but your garden and your plants will be much better off if you wait for spring. In cold climates, the skeleton of the plant helps collect snow to protect the sensitive crown (where next year's growing tips will emerge). Furthermore, the herbaceous parts of the plant will replenish nutrients in the soil as their leaves break down over winter. Leaving the tops on provides a place for ladybugs to overwinter, helping to keep aphid populations in check, and seeds can feed the birds. However, if you feel you really must cut them back, leave at least six inches to help collect snow and protect those crowns.

5. Make my garden grow and grow.

Propagation of perennials can be done in a number of ways. The number one way in this part of the world is through division of the roots so that one hosta, for example, can become many. Division not only increases your plant population, it adds new life to old plants, extending their longevity and rejuvenating large clumps that have started to die back in their centres as the hearts become starved of nutrition. You can also grow perennials from seed. Fortunately, the easiest seed starters are the short-lived perennials. Perennials can also be increased by taking soft tissue stem or root cuttings, just as you would start a new houseplant.

6. Ephemerals.

Some plants are known as spring ephemerals. These are perennial plants that emerge early in the year and die back to their roots after a short time of blooming and producing seed. These would include trillium, Virginia bluebells, foamflower (Tiarella cordifolia) and bloodroot. Other plants not officially in this category but whose leaves die back (usually early in summer) after the plant flowers include columbine, Oriental poppies and celandine poppies. Purists would not include spring flowering bulbs in this category, but they too die back after flowering. It's best to plant something nearby that matures a little later and will fill in the spaces once this happens.

7. Zoning in and out.

Technically, much of Canada is zone 3, but the extremes range from the Arctic (zone 0) to the southern tip of Ontario (zone 7) and parts of Vancouver Island (zone 8). However, the hardiness zone map was originally designed to measure the hardiness of woody plants such as trees and shrubs and is not that accurate when it comes to perennials. All sorts of variables affect the tolerance of plants to winters in Canada, not just the winter temperature. Soil, moisture, wind exposure, sunlight, proximity to large bodies of water, and elevation are just a few. So don't be afraid to push the envelope when trying out plants. You'd be surprised what you can grow in your zone, because the microclimate in your back yard may be a few degrees higher than you think. Zone 3 can often overwinter plants as "cold" intolerant as zone 5 and there are cases where even that has been exceeded.

8. Creating a microclimate for perennials.

A south-facing, sheltered place that gets plenty of snow cover is a good start. Adding sheltering trees such as evergreens, windbreaks like latticed arbours, and good rich soil can extend your zone and your growing season. In Britain, they used to wall vegetable gardens to extend their growing season and grow more exotic crops. Remember, cold air sinks and hot air rises. Planting next to a foundation or over a septic tank will alter the climate.

9. A time to reap and a time to sow, a time to divide and to use the hoe.

When should you think about propagating your plants? Cuttings are best taken in spring when plants are in a growth mode. There is no single perfect time for dividing plants, although the rule of thumb has been to divide fleshy-rooted plants, such as iris, in late summer so that the roots have a chance to build up reserves against the coming winter. The rule-makers also advise you to divide flowering plants right after they have finished blooming. My rule says don't divide just before plants bloom or while they are blooming. In clay soils, which can become very hard and dry in late summer, division of most plants is best done in springtime when the soil is still friable or workable and when roots can more readily re-establish.

10. Watering and fertilizing.

If you understand the moisture and climate needs of your perennials, chances are you won't have to water often or at all unless there is a drought. Once the roots are well established, you need only water if your plants appear to be parched or are struggling for growth. You should also water if you plan to fertilize. Should you fertilize? That depends on the amount of care you put into the soil you planted in. Good soil with the right moisture content for the requirements of the plant will provide the nutrientS your perennials need. If you feel you must provide your plants with a boost, for most of them a balanced fertilizer (all three numbers the same) will do just fine.

- Dorothy Dobbie Copyright© Pegasus Publications Inc

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