In Canada, we refer to geographical regions called Hardiness Zones to determine which plants are suitable to grow in a given part of the country. Many of our trees, shrubs, and perennials have a number assigned to them which indicates where they are suited to grow.

What do the numbers mean?

In Canada, we have climate zones ranging from 0 to 9. Each number is also subdivided into “a” and “b”. Generally speaking, the lower the number is, the colder the climate is in that region, and most zones are assigned a minimum yearly temperature.

Resolute, Nunavut is Zone 0a, while Victoria, BC is Zone 8b. Of course, it’s not entirely that simple – the number is representative of a number of factors, not just temperature – it also takes into account average yearly precipitation, wind, and so on. For our purposes as gardeners, however, the number is a quick and easy way to help decide if a plant is suitable for our garden.

What Zone am I?

London and the surrounding region are considered to be Zone 6a or Zone 6b. This means that any plant you purchase that is indicated as Zone 6 or lower is suitable for our climate. A Zone 9 plant would almost certainly die over the winter in London. A Zone 3 plant, conversely, would do just fine.

Zones as Guidelines

It’s important to be aware that these Hardiness Zones are not absolute. Every house and area of the city can have its own special conditions, which we often refer to as a “microclimate”. You could have a warm microclimate where normally tender plants survive, or a cold exposed area at the top of a hill where only Zone 4 plants seem to do well.

In addition, we could have an unusually warm winter where some of your annuals actually survive. Or we might have an unseasonably cold winter where you lose plants that should otherwise be hardy for this area. For this reason, we recommend that Zone 6 plants be planted in a sheltered area where they are protected from cold temperatures and wind in the winter.

Other Countries Are Different

When we peruse websites for new or interesting plants to inspire us, it’s easy to forget that websites for nurseries and greenhouses in the United States or other countries may use a different method of criteria when it comes to plant hardiness. The United States has a similar system to Canada with numbers ranging from 0 to 11, and certainly there is some cross over, but it is always a good idea to ask our knowledgeable staff if a plant is suitable for the London area. Certainly, the UK has completely different criteria from North American standards.

The easiest way to avoid this is to always ensure you’re looking on a Canadian website.

A common question faced by gardeners is what to plant in shady areas. Many plants are shade-tolerant and thrive without direct sunlight. To grow healthy plants in shady areas, it is important to consider the degree of shade that a plant needs or will tolerate. Choose from the plants listed below to brighten up a shady landscape with beautiful flowers and foliage.

Evergreen Trees

Junipers for Light Shade

Austrian Pine Blue Rug
Douglas Fir Buffalo, Calgary Carpet etc.
Hemlock Effusa
Other False Cypress Japanese Garden Juniper
Scot’s Pine Mountbatten, Skyrocket and Spartan
Weeping False Cypress Savin & the Savina Group-Tamarix
White Pine

 

Evergreen Shrubs – Needled and Broadleaf

Alberta Spruce *Dwf Hemlocks Mugho Pine
*Boxwood Dwf Serbian Spruce *Oregon Grape Holly
Burkwood Viburnum *Euonymus varieties *Pieris
Cedars, particularly dwarf varieties Firethorn *Rhododendron & Azalea
Daphne cneorum Holly(many varieties) *Yew (all varieties)
Dwf False Cypress *Mountain Laurel (Kalmia)

 

Deciduous Trees

Dawn Redwood Katsura Tree Red Bud
Flowering Dogwood Laburnum Saucer Magnolia
Halesia (Silverbell) Mountain Ash Star Magnolia
Ivory Silk Lilac Pagoda Dogwood

 

Deciduous Shrubs

All Viburnums including Dogwoods Mock Orange
Azaleas, Exbury types Elders Other Hazels
Bayberry Flowering Almond Potentilla
*Bottlebush Buckeye *Flowering Currants Serviceberry
*Burning Bush Honeysuckle Snowball and Fragrant Snowball
Carolina Allspice Hydrangeas *Snowberry & Coralberry
Cork Screw Hazel Japanese Maple Tree Peony
Cotoneasters *Kerria Winterberry
Deutzias Manchu Cherry Witch Hazel

* Are plants that will thrive in deep shade

Perennials for Shade

Aconitum Columbines *Hosta Purple Coneflower
Anchusa Coral Bells Jacob’s Ladder Purple Loosestrife
Arabis Cranesbills Japanese Anemone *Saxifrage
*Astilbe *Creeping Jenny Leopard’s Bane Shasta Daisy
Balloon Flower Day Lily Lupins Siberian Iris
Bergenia Feverfew Macleaya *Solomon’s Seal
*Bethlehem Sage Fillipendula Marsh Marigold *Spiderwort
Bleeding Heart Foxglove Meadowrue Tall Phlox
Brunnera Garlic Chives Monarda (Bergamot) Trillium
Cardinal Flower Gas plant Nepata Trollius
Carpathian Harebell Geum Obedient Plant Veronica
Chives Globe Thistle Oriental Poppy Viola
Christmas Rose Goatsbeard Painted Daisy –light shade *Virginia Bluebells
Chrysanthemum Gold Moss Peony Yellow Loosestrife
Cimcifuga Gooseneck Primrose

 

Perennial Groundcovers

Ajuga English Ivy Lily-of-the-Valley
*All Ferns *Epimedium Many Ornamental Grasses
Creeping Potentilla Euonymus *Pachysandra
Cotoneasters *Goutweed Periwinkle
Crown Vetch Hall’s Honeysuckle Virginia Creeper

 

Annuals for Shade

Begonias Fuchsia Nicotiana
Bells-of-Ireland *Goutweed Pansies
Black-eyed-Susan Vine *Impatiens Salvia
Caladium Iresine Schizanthus
Clarkia/Godetia Martha Washington Geranium Snow-on-the Mountain
*Coleus Mimulus Sweet William
Forget-me-not Neirembergia *Torenia

 

Vines

Bittersweet *English Ivy
*Boston Ivy *Euonymus
Climbing Honesuckle Some Clematis varieties
*Climbing Hydrangea *Virginia Creeper

*Are plants that will thrive in deep shade

Some landscapes have areas that accumulate more water than others due to poor drainage, low lying areas, or a number of other reasons. Despite these conditions and with the right plants you can still achieve an attractive and interesting garden. The plants listed here will thrive in moist, wet areas.

Perennials that do well in moist areas

Astilibe Hemerocallis
Aruncus Iris Ensata
Bergenia Lobelia Cardinals
Chelone Ligularia
Cimicifuga Lythrum
Convallama Physostegia
Eupatorium Primula
Ferns Rodgersi
Filipendula

Designing a garden to withstand dry periods doesn’t mean sacrificing colour and variety. There are a number of drought-tolerant plants suitable for the dry and sunny locations in your landscape. The ones listed here are excellent choices that adapt well to dry conditions.

Perennials that do well in dry areas

Achillea                 Fla
Asclepsia Guara
Amsonia Lambs Ear
Armeria Russian Sage
Artemesia Yarrow
Coreopsis Threadleaf

 

Annual Plants for Sun

Ageratum Marigolds
Alyssum Morning Glory
Asters Petunias
Carnation Portulaca
Celosia Salvia
Coleus Snapdragons
Dahlia Sunshine Impatiens
Dusty Miller Verbena
Geraniums Zinnia

Knowing what kind of soil you have around your property as well as understanding the implications of certain soil types is very important in ensuring that you pick the right plants for your yard. The right combination of soil and shrub will save you money as well as hours upon hours of work in the future.

Most of the soil in the London area is either sandy or heavy clay. If you’re not sure what you have, use this simple test: squeeze a ball of moist soil in your hand. If the soil compresses tightly in your hand and keeps its shape when you release it, you have clay. If it begins to crumble apart when you release it, you have sand. Both soil types present their own challenges.

Heavy Clay Soil

The greatest difficulty with heavy clay soil is that it drains poorly. Plants that do not like “wet feet” will die or develop poor or stunted growth over a number of years. Those that do not die will be left susceptible to diseases and pests. Also of issue is that clay soils tend to be slightly alkaline: acid-loving plants will develop iron and nitrogen deficiencies when planted in clay. Luckily, there are quite a few simple solutions to these issues:

  • The easiest solution, of course, is to plant shrubs that enjoy excess moisture, poor drainage, and slight alkalinity; no other adjustments will be needed
  • The bacteria present in manure and compost can help to break down thick layers of clay in the ground. Use soils such as Triple Blend or Compost Plus to speed this process. Organic material also helps with drainage and ensures there is an adequate supply of air for the roots underground
  • When planting, dig your hole and then use a spade to vigorously break up the clay directly below the bottom of the hole; this will improve drainage
  • If even the surface of the soil is thick with clay, be sure to dig your hole far wider than you normally would and backfill this with a mixture of ½ the original soil and ½ organically rich, new soil
  • Use Rhododendron and Azalea food to combat the alkalinity of heavy clay soils

Sandy Soil

Sandy soil presents a different challenge than clay: it drains a little too well. If you have very sandy soil, you will have a great deal of difficulty growing plants that require consistent water levels or aren’t generally drought-tolerant. Nutrient values are also generally poor in very sandy soil. However, the solutions are even easier than with clay:

  • First and foremost, try planting shrubs that can tolerate low-nutrient, dry soils; if you do this, extra maintenance will be kept to a minimum
  • Use an abundance of nutrient-rich, dark soil (such as Triple Blend) and ideally a small amount of peat moss to help the soil retain moisture more effectively
  • Dig your planting holes slightly wider and much deeper. Backfill the hole with better soil up to the proper planting depth, then place the plant in the hole. This will encourage your new planting to root deeper in the soil where water is more abundant

The table below will give some suggestion on what to plant in these difficult areas. Note that this list is based on more extreme situations – if you have just a little bit of clay or sand, you generally have nothing to worry about.

Trees and Shrubs Tolerant of Clay Trees and Shrubs Intolerant of Clay Trees and Shrubs Tolerant of Sand Trees and Shrubs Intolerant of Sand
Aspen/Poplar Apricot Fiveleaf Aralia Azalea
River Birch Azalea Bayberry Flowering Dogwood
White Cedar Beech Bluebeard Elder
Chokeberry Blueberry Cotoneaster False Cypress
Dogwood Bog-Rosemary Juniper Fothergilla
Elder Cherry Weeping Peashrub Hydrangea
Balsam Fir Holly Pine Katsura
Sweet Gale Juniper Potentilla Pieris
Honey-Locust Jap. Tree Lilac Sea-Buckthorn Rhododendron
Kentucky Coffeetree Peach Snowberry Carolina Silverbell
Larch/Tamarack Persian Witch-Hazel St. John’s Wort Summersweet
Red/Silver Maple Pieris Sumac Willow
Ninebark Rhododendron Tamarix
Burr Oak Carolina Silverbell Turkish Hazel
Sycamore Colorado Spruce
Willow Tulip Tree
Winterberry Jap. Umbrella Pine
Witch-Hazel Yew