Choosing between annuals and perennials is one of the first decisions gardeners make when planning a planter. Both can thrive in raised cedar planters, but they behave very differently from season to season.

Annuals are ideal if you want fast growth, abundant flowers and the freedom to redesign your planter every year. Perennials, on the other hand, can return for several years and provide long-term structure and seasonal interest.

For Ontario gardeners, the best choice often isn't one or the other. Combining annuals and perennials can create a planter that looks attractive from spring through fall while still providing plants that return the following year.

Natural Resources Canada maintains Canada's official Plant Hardiness Zone system, which helps gardeners determine which perennial plants are suited to their local climate. Ontario covers a wide range of growing conditions, so gardeners should check their specific municipality rather than assuming that a plant suited to Southern Ontario will perform equally well throughout the province.

Check your Canadian Plant Hardiness Zone – Natural Resources Canada

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What Is the Difference Between Annuals and Perennials?

The main difference is their life cycle.

Annuals

Annual plants complete their entire life cycle in a single growing season. They germinate, grow, flower, produce seed and die, usually after the first hard frost.

Popular annuals for Ontario planters include:

• Petunias
• Marigolds
• Geraniums
• Calibrachoa
• Begonias
• Impatiens
• Lobelia
• Sweet alyssum
• Coleus

Because annuals only have one growing season in which to reproduce, many varieties flower exceptionally heavily throughout summer.

Perennials

Perennials live for multiple years. The foliage of many varieties dies back during the Canadian winter, while the crown and root system remain dormant before producing new growth the following spring.

Popular perennials for planters can include:

• Lavender
• Coneflower
• Black-eyed Susan
• Sedum
• Heuchera
• Hosta
• Hardy geranium
• Ornamental grasses
• Chives
• Certain varieties of thyme

Whether a perennial survives winter successfully depends on the variety, your location, winter exposure and whether it is planted in the ground or in a container.

Important: perennial roots growing in an elevated planter are more exposed to winter temperatures than roots insulated by the surrounding ground. Choose hardy plants carefully if you intend to leave them outdoors all winter.

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Annuals provide immediate colour, while perennials can form the long-term foundation of a planter.

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Benefits of Growing Annuals

Annuals are especially useful in raised planters because they establish quickly and can provide colour for most of the gardening season.

Continuous colour

Many annuals flower from late spring until frost when they receive appropriate water, nutrients and deadheading.

Petunias, calibrachoa, marigolds and geraniums are particularly useful for creating dramatic displays.

Freedom to change your garden every year

One of the great advantages of annuals is flexibility.

You might create a bright red-and-yellow planter one year and switch to white, purple and silver foliage the following season.

This is particularly useful for patios, entrances and outdoor entertaining areas where the planter forms part of the overall décor.

Excellent for filling gaps

Annuals grow quickly, making them excellent companions for slower-growing perennial plants.

They can fill empty areas while perennials mature.

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Benefits of Growing Perennials

Perennials are valuable when you want a more permanent planting scheme.

Plants return year after year

A well-chosen perennial can remain part of your planter for several seasons rather than needing to be replaced each spring.

Long-term structure

Plants such as ornamental grasses, lavender, sedum and coneflowers can become the architectural foundation of a planter.

Annual flowers can then be added around them each spring.

Seasonal interest

Different perennials flower at different times.

By combining early-, mid- and late-season flowering plants, you can create a planter that changes throughout the growing season.

Established root systems

Perennials develop larger root systems over time. This makes adequate planter volume, drainage and good-quality soil particularly important.

Timber Roots planters have a generous 24-inch growing width, providing more root space for mixed flowers, herbs and vegetables than narrower planter designs.

Explore Timber Roots cedar planters and raised garden beds

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Annuals and Perennials in Ontario's Climate

Ontario presents gardeners with both opportunities and challenges.

Warm summer conditions support an enormous range of flowering plants, herbs and vegetables, but winter temperatures determine which perennials can reliably return the following spring.

Natural Resources Canada's updated hardiness mapping uses several climate variables—including minimum winter temperatures, frost-free period, rainfall, snow depth and wind—to help determine perennial survival.

Southern Ontario

Areas around the Greater Toronto Area and other parts of Southern Ontario generally have longer growing seasons than northern areas of the province.

Even within the same city, however, microclimates matter.

A planter against a south-facing brick wall may experience considerably different conditions from one positioned on an exposed deck.

Northern and colder regions

In colder areas, the selection of overwintering perennials becomes more important.

Plants that survive comfortably in the ground may experience greater temperature fluctuations in an elevated planter.

For that reason, gardeners intending to overwinter perennials should favour plants comfortably hardy for their local conditions, rather than plants at the very limit of their hardiness range.

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How Much Sun Does Your Planter Receive?

Before choosing any plants, observe the planter location.

As a practical guide:

Always check the plant label because requirements vary by species and cultivar.

Don't mix incompatible plants

A common gardening mistake is selecting plants primarily because their colours look attractive together.

Plants sharing a planter should ideally have similar requirements for:

• sunlight
• soil moisture
• drainage
• fertility

For example, a drought-tolerant lavender plant is not an ideal companion for a moisture-loving plant that requires constantly damp soil.

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PHOTO 2 – Sun-location photograph
Photograph a Timber Roots planter positioned on a sunny patio or deck.
Alt text: Cedar raised planter positioned in full sun on an Ontario patio
Caption: Observe how many hours of direct sunlight your planting location receives before selecting plants.

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What Should You Plant in Different Planter Sizes?

The size of the planter influences how many plants can be combined and how much root space is available.

24" × 24" Cedar Planter

The 24" × 24" Cedar Planter Box is particularly useful for a compact floral display, herb garden or carefully selected mixed planting.

View the 24" × 24" Cedar Planter Box

Try:

Sunny flower combination

• 1 upright geranium
• 2–3 petunias
• trailing calibrachoa or sweet alyssum around the edges

Perennial combination

• 1 compact coneflower
• 2 heuchera
• trailing sedum

Herb planter

• Parsley
• Chives
• Thyme
• Basil

Remember that vigorous herbs such as mint are often better kept in their own container because they can overwhelm neighbouring plants.

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36" × 24" Cedar Planter

A longer planter gives you more room for layering plants by height.

The Timber Roots 36" × 24" Cedar Raised Garden Planter is designed for mixed plantings of vegetables, herbs, flowers and ornamental plants.

View the 36" × 24" Cedar Raised Garden Planter

Consider:

Pollinator combination

• Coneflowers
• Salvia
• Marigolds
• Sweet alyssum

Or:

Summer colour combination

• Geraniums toward the centre
• Petunias around them
• Calibrachoa or lobelia trailing over the edges

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48" × 24" Cedar Raised Garden Bed

A larger planter allows you to create a miniature garden rather than a simple container arrangement.

The 48" × 24" Large Cedar Raised Garden Bed provides four feet of planting length and works particularly well for larger mixed plantings.

View the 48" × 24" Large Cedar Raised Garden Bed

Possible combinations include:

Perennial foundation + annual colour

• Ornamental grass as the focal point
• Coneflowers or black-eyed Susans
• Heuchera
• Petunias or calibrachoa along the edge

Or create an edible garden with:

• Tomatoes
• Peppers
• Basil
• Parsley
• Marigolds

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Hexagonal Cedar Planters

Smaller planters often work particularly well when treated as a single focal display.

A Timber Roots Hexagonal Cedar Planter can accommodate flowers, herbs, ornamentals and compact shrubs.

View the Hexagonal Cedar Planter

Try one dramatic centre plant surrounded by lower-growing or trailing annuals.

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Alt text: 

Larger cedar planters make it easier to combine structural perennials with seasonal annual colour.

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Try the "Thriller, Filler and Spiller" Method

A simple method for designing an attractive planter is to combine three growth habits.

Thriller

A taller focal plant.

Examples:

• Ornamental grass
• Geranium
• Salvia
• Compact coneflower

Filler

Medium-height plants that provide colour and volume.

Examples:

• Marigolds
• Begonias
• Heuchera
• Petunias

Spiller

Plants that trail over the edge.

Examples:

• Lobelia
• Sweet alyssum
• Calibrachoa
• Trailing petunia

You don't have to follow this formula rigidly, but it provides a useful starting point when planning a mixed planter.

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Can Perennials Stay in a Cedar Planter Over Winter?

Some can—but overwintering plants in containers requires more care than overwintering the same plants in the ground.

The soil inside an elevated planter is exposed to cold air from multiple directions and therefore experiences greater temperature fluctuations.

If you want to overwinter perennial plants:

• Choose plants well suited to your local Canadian hardiness zone.
• Avoid allowing the soil to remain waterlogged.
• Ensure drainage remains functional.
• Move movable planters to a more sheltered location where practical.
• Protect plants from severe winter wind.
• Add mulch after the soil begins cooling to moderate temperature fluctuations.
• Avoid heavy fall fertilization that encourages tender new growth immediately before winter.
• Check soil moisture periodically during prolonged dry periods before freeze-up.

For valuable or marginally hardy specimens, transferring the plant to a protected location may be safer.

The planter itself can remain outdoors. Western Red Cedar's natural resistance to moisture and decay is one of the reasons Timber Roots uses it for outdoor raised planters.

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What About Annuals at the End of the Season?

Once frost has finished your annual display:

1. Remove dead plants.
2. Remove obviously diseased foliage rather than composting it.
3. Check the soil surface for weeds.
4. Top up soil or compost as required.
5. Leave healthy perennial plants in place if you intend to overwinter them.
6. Plan next year's planting while you can still remember what worked well.

This annual refresh is also an opportunity to change colours or experiment with new varieties.

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Should You Choose Annuals, Perennials—or Both?

For most Ontario planter gardens, a combination of both provides the greatest flexibility.

Annuals provide:

• immediate colour
• long flowering periods
• easy seasonal changes

Perennials provide:

• structure
• continuity
• repeat growth
• long-term value

A particularly effective strategy is to establish a few hardy perennial "anchor" plants and surround them with annuals that can be changed every spring.

That gives your planter a permanent framework without sacrificing the fun of creating a new display each year.

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PHOTO 4 – Final lifestyle photograph
Use one of your strongest Timber Roots photographs showing a fully planted planter in an attractive garden or patio setting.
Alt text: Handcrafted Canadian cedar planter filled with summer flowers
Caption: Combining annuals and perennials can provide both immediate colour and long-term structure.

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More Gardening Ideas from Timber Roots

Planning a vegetable garden as well as flowers? Read Grow the Best Vegetables This Spring, which covers cool-season and warm-season vegetables suitable for Canadian gardens.

Grow the Best Vegetables This Spring

You may also be interested in the benefits of using all-wood cedar planters for outdoor gardening.

Read: All Wood Cedar Planters

Or browse the complete Timber Roots range of handcrafted Western Red Cedar planters, including 24", 36", 48" and hexagonal designs. Timber Roots' current planter collection is handcrafted in Ontario and intended for flowers, herbs, vegetables and ornamental plants.

Shop Cedar Planters & Raised Garden Beds