Best Plants for London, Ontario Gardens: A Complete Zone 6 Guide

March 1, 2026 · 8 min read

Choosing the right plants is the single most important decision you can make for your London, Ontario garden. London sits squarely in USDA Hardiness Zone 6a (Canadian Zone 5b), which means winter lows of –25°C to –20°C and hot, humid summers. Pair that with the heavy clay soils found across most of the city, and you need plants that are genuinely tough — not just pretty on the garden-centre shelf. This guide covers the trees, shrubs, perennials, grasses, and ground covers that our landscape design team recommends for lasting, beautiful results.

Shade Trees: The Backbone of a London Landscape

Large deciduous shade trees cool your property in summer, reduce energy costs, and add significant value to your home. London's streets are lined with mature examples, and planting one today is an investment that pays dividends for decades.

• Sugar Maple (Acer saccharum): Ontario's signature tree. Brilliant orange-red fall colour, tolerates clay, and thrives in full sun to part shade. Expect heights of 20–25 metres at maturity.
• Red Oak (Quercus rubra): A native powerhouse that grows faster than most oaks and handles London's clay well. Deep root system means less sidewalk heaving. Excellent russet-red fall foliage.
• Serviceberry (Amelanchier canadensis): A smaller native option (6–8 m) perfect for urban lots. White spring flowers, edible berries, and orange-red autumn leaves. Attracts songbirds.
• Hackberry (Celtis occidentalis): An underused native shade tree with excellent drought tolerance once established, naturally resistant to most pests, and unbothered by road salt — ideal for front yards near London streets.

Ornamental Trees for Four-Season Interest

Smaller ornamental trees work in tight spaces, as focal points in garden beds, or as understory plantings beneath larger canopy trees.

• Eastern Redbud (Cercis canadensis): Magenta-pink flowers in early spring before leaves emerge. Hardy to Zone 5 and handles London's clay. Stays compact at 6–9 metres.
• Japanese Maple (Acer palmatum): Select Zone 5–hardy cultivars like 'Bloodgood' or 'Emperor I'. Plant in a sheltered spot protected from winter winds. Stunning as a specimen in a courtyard or front garden.
• Ivory Silk Lilac Tree (Syringa reticulata): Fragrant white flower clusters in June, disease-resistant, and widely planted by the City of London for good reason — it's virtually maintenance-free.

Evergreen Shrubs: Year-Round Structure

Evergreens provide privacy screening, winter garden interest, and a green backdrop that makes flowering plants pop. They're essential to any well-designed London landscape.

• Emerald Cedar (Thuja occidentalis 'Smaragd'): London's most popular privacy hedge. Dense, narrow form, no pruning needed, and fully hardy. Plant 60–90 cm apart for a solid screen.
• Boxwood (Buxus 'Green Velvet' or 'Green Mountain'): These hardy cultivars were developed in Ontario and reliably survive London winters. Excellent for low hedges, borders, and formal garden structure.
• Mugo Pine (Pinus mugo): A compact, slow-growing conifer that thrives in full sun and tolerates poor, dry soils. Deer leave it alone.
• Blue Star Juniper (Juniperus squamata): Low-growing, steel-blue foliage that contrasts beautifully with perennials. Extremely drought-tolerant once established.

Flowering Shrubs: Colour from Spring Through Fall

Nothing elevates a garden like well-chosen flowering shrubs that bloom in succession from May through October.

• Hydrangea: 'Limelight' (panicle type) is the most reliable performer in London. Full sun, clay-tolerant, and blooms from July to frost on new wood — so even after a harsh winter, you get flowers. 'Annabelle' (smooth hydrangea) thrives in shadier spots.
• Ninebark (Physocarpus opulifolius): A native Ontario shrub with dramatic burgundy or gold foliage depending on cultivar. 'Diablo' and 'Amber Jubilee' are top picks. Extremely tough, drought-tolerant, and deer-resistant.
• Common Lilac (Syringa vulgaris): Fragrant May blooms in purple, white, or pink. Lilacs love London's alkaline clay soils and cold winters, which they need for proper bud set. A classic that never goes out of style.
• Weigela: 'Wine and Roses' and 'Sonic Bloom' cultivars provide tubular flowers that attract hummingbirds. Reblooming varieties extend the show from June through September.

Perennials: The Heart of a London Garden

Perennials return year after year, filling garden beds with colour, texture, and seasonal interest. Choose a mix that ensures something is blooming from May through October.

• Purple Coneflower (Echinacea purpurea): Native to Ontario, drought-tolerant once established, blooms for weeks in July–August, and attracts pollinators. Leave seed heads standing for winter bird food and garden structure.
• Black-Eyed Susan (Rudbeckia): Another native Ontario wildflower that self-seeds gently and lights up late summer with golden-yellow blooms. 'Goldsturm' is the go-to cultivar for garden beds.
• Hosta: The undisputed queen of shade gardens in London. Hundreds of cultivars range from six-inch miniatures to giant four-foot specimens. 'Halcyon', 'Sum and Substance', and 'Patriot' are proven performers in clay soil.
• Astilbe: Feathery plumes of pink, red, white, or purple brighten shady spots from June to August. Prefers moist soil, which makes it a natural fit for London's heavier clays that retain moisture.
• Daylily (Hemerocallis): Nearly indestructible. 'Stella de Oro' repeats all summer, while named varieties offer every colour except true blue. Handles full sun, clay soil, and drought without complaint.
• Catmint (Nepeta): Lavender-blue spikes from June through frost if you shear spent blooms. Deer-proof, drought-proof, and a magnet for bees. 'Walker's Low' is the most popular cultivar and pairs beautifully along walkways and hardscaped patios.

Ornamental Grasses: Movement and Texture

Grasses add a modern, naturalistic element to London gardens and look especially striking through fall and into winter when their seed heads catch frost and light.

• Karl Foerster Feather Reed Grass (Calamagrostis): Narrow, upright form works in tight spaces. Blooms in June, holds structure all winter. Zone 4 hardy — no trouble in London.
• Switchgrass (Panicum virgatum): A native Ontario prairie grass. 'Shenandoah' turns wine-red in fall. Deep roots make it excellent for erosion control and it thrives in clay.
• Blue Fescue (Festuca glauca): A compact ornamental grass with striking steel-blue foliage that stays under 30 cm. Perfect as edging or in rock gardens. Deer-resistant and drought-tolerant.

Ground Covers: Living Mulch for Problem Areas

Ground covers suppress weeds, reduce erosion, and eliminate mowing in areas where grass struggles — under trees, on slopes, or in narrow side yards.

• Wild Ginger (Asarum canadense): A native Ontario ground cover for deep shade. Heart-shaped leaves form a dense carpet. Deer-resistant.
• Creeping Thyme (Thymus serpyllum): A sun-loving, walkable ground cover that produces pink-purple flowers in early summer and releases a pleasant fragrance when stepped on. Perfect between flagstone pavers.
• Sweet Woodruff (Galium odoratum): White spring flowers and whorled leaves that form a lush mat in shade. Spreads readily in moist clay — ideal under mature trees where grass won't grow.

Working with London's Clay Soil

Most of London sits on heavy clay, which can be both a blessing and a curse. Clay retains moisture and nutrients well, but it drains slowly and compacts easily. Here's how to work with it rather than against it:

• Amend at planting time: Mix compost or aged manure into backfill when planting. This improves drainage and soil structure around root zones.
• Mulch generously: A 7–10 cm layer of shredded bark or wood chips keeps clay from drying into concrete-hard crust in summer and moderates soil temperature year-round.
• Choose clay-tolerant species: The plants in this guide were selected specifically because they handle London's clay. Avoid species that demand sandy, fast-draining soil — they'll struggle here.
• Improve drainage where needed: If water pools in your yard after rain, you may need grading adjustments or a French drain before planting. Our landscaping team can assess drainage on-site.

Deer-Resistant and Drought-Tolerant Picks

London homeowners near ravines, woodlots, or the Thames River corridor know the heartbreak of deer-browsed gardens. For deer-prone areas, prioritize ninebark, catmint, ornamental grasses, boxwood, and mugo pine. Deer generally avoid plants with strong scents, fuzzy or prickly textures, and toxic compounds.

Drought tolerance matters more each year as summers grow hotter. Once established (usually after one full growing season), coneflower, black-eyed susan, switchgrass, catmint, daylily, and juniper can handle extended dry spells without supplemental watering.

Get Expert Help Choosing the Right Plants

A well-planned plant selection is the difference between a garden that thrives for years and one that needs constant replacement. Our landscape design service includes detailed planting plans with species selected for your specific site conditions — sun, soil, drainage, deer pressure, and your personal style preferences.