Container gardening transcends mere horticultural convenience; it’s a creative rebellion against spatial limitations. Introducing trees in pots allows gardeners to infuse not only colour, texture, but a vertical drama and scale into terraces, rooftops, or entryways.

Imagine a Japanese maple’s fiery autumn foliage juxtaposed against a quiet lake or a potted olive tree softening a minimalist courtyard. These living sculptures not only anchor designs but also evolve with the seasons, offering ever-changing visual interest.

However, nurturing trees in containers demands nuanced care. It’s a dance between art and botany. Success hinges on understanding each species’ needs and tailoring conditions accordingly—far more complex than plopping a sapling into dirt.

In this guide we will accompany you through the journey of learning all about planting trees in pots. These are the topics that will be covered.

Why Trees in Plant Containers?

Research conducted by the National Gardening Association underscores the benefits of container gardening, emphasising improved water management and the ability to create tailored soil mixes that cater to the specific needs of different plant species.

Furthermore, studies in urban forestry, such as those published by the Arbor Day Foundation, highlight the vital role of urban trees, even those in containers, in mitigating the urban heat island effect and improving air quality.

Jamie Durie, famous Australian Garden designer and TV personality eloquently summarises this adaptability:

“Beyond the practical, the ability to effortlessly rearrange potted trees to revitalise a landscape or adapt to evolving needs is a game-changer! You simply can’t achieve that with trees permanently rooted in the earth…” This dynamic quality allows for seasonal transformations and the continuous evolution of outdoor aesthetics.

For businesses, investing in a thoughtfully designed landscape featuring strategically placed container trees translates into a tangible financial advantage by enhancing visual appeal and fostering inviting outdoor spaces for patrons and clients alike.

The strategic deployment of tree planters can redefine outdoor spaces. Restaurants can delineate al fresco dining areas, hotels can create welcoming and verdant entrances, and retailers can enhance their curb appeal, all through the thoughtful placement of container-grown trees that introduce colour, order, and textural richness.

Selecting Pots

Cultivating plants within the confines of containers presents a dynamic approach to enriching our outdoor environments. Trees, in particular, bestow a sense of tranquillity, natural beauty, and a touch of untamed wilderness upon any landscape design.

However, the art of nurturing trees in confined spaces demands thoughtful consideration. Success hinges on understanding and addressing several key factors that differ from traditional in-ground planting. One of the initial and often overlooked aspects is the selection of the container itself.

The world of containers offers a diverse palette of materials, each with its own set of characteristics. Concrete endows a sense of permanence, plastic offers lightweight versatility, resin provides durability with design flexibility, and classic clay exudes timeless charm. The optimal choice of container is intrinsically linked to the well-being of your potted tree, holding equal importance to the selection of the growing medium.

The most suitable containers for trees possess the inherent strength and resilience to endure the rigours of outdoor exposure for years, all while retaining their aesthetic appeal. While the substantial weight of clay pots ensures stability, lighter plastic alternatives may prove vulnerable to strong winds.

Our meticulously crafted planters offer a superior solution. Engineered from robust fiberglass resin, they are inherently weatherproof, resistant to fading under the sun’s gaze, and impervious to rust. Furthermore, their composition ensures that no harmful chemicals leach into the surrounding landscape, safeguarding the health of your plants and the environment.

Clay and Terracotta: Classic yet heavy, these porous pots promote root aeration, ideal for Mediterranean species like citrus or figs. However, they crack in freezing temps and require frequent watering.

Plastic and Resin: Lightweight and affordable, these mimic natural materials but may degrade under UV exposure. Opt for UV-stabilised variants for longevity.

Fiberglass Reinforced Resin: A premium choice, combining durability with featherlight portability. Brands like Sigma Planters offer frost-proof, fade-resistant designs that come with long-lasting warranties.

Concrete and Metal: Industrial-chic options suit contemporary settings but may retain heat, stressing roots. Line with insulating foam or avoid for heat-sensitive species.

Design Considerations

The below project of topiary trees in large plant containers offers a great example of careful consideration of several design principles to ensure both the aesthetic appeal and the long-term health of the trees.

Scale and Proportion:

The size of the tree and the planter must be in proportion to the surrounding space and each other. The tree shouldn’t overwhelm the planter, nor should the planter appear too small for the tree. The three topiary trees in their square, dark-colored planters seem appropriately scaled for the width of the walkway and the height of the adjacent brick wall and building. They provide a noticeable vertical element without feeling cramped or out of place.

Unity and Harmony:

The style, material, and color of the planters should harmonise with the architectural style of the building and the overall landscape design. The simple, geometric shape and the dark, neutral color of the planters offer a sense of modern simplicity that complements the brickwork and the clean lines of the white building in the background. The repetition of the same planter style for all three trees creates a sense of unity and visual rhythm.

Rhythm and Repetition:

Repeating elements like the type of tree, the style of the planter, or their spacing can create a sense of rhythm and visual flow.The consistent use of the same type of topiary tree and the identical square planters, placed at regular intervals along the walkway, establishes a clear and pleasing rhythm, guiding the eye along the entrance.

Emphasis (Focal Point):

While a grouping of identical trees can create a sense of rhythm, a single, more distinctive tree or planter can serve as a focal point. In this particular arrangement, the emphasis is on the linear progression and the uniform appearance of the three topiaries, rather than a single focal point. However, if one of these trees were different in size, shape, or if its planter stood out, it could become a focal point.

Balance:

Consider the visual weight and distribution of the planted trees and their planters in relation to the surrounding elements. Symmetry can create a formal balance, while asymmetry can offer a more natural feel. The symmetrical placement of the three trees along the raised walkway creates a sense of formal balance, which is often suitable for entrance areas.

Functionality and Circulation:

The placement of planters with trees should not impede pedestrian flow or access. The planters are positioned neatly along the side of the walkway, leaving ample space for people to walk by without obstruction.

Plant Selection and Growth Habits:

Choose tree species that are suitable for container planting and consider their mature size and growth habits. Ensure the planter is large enough to accommodate the root system and allow for healthy growth. The topiaries appear to be species that tolerate being pruned and maintained in a relatively compact shape, making them suitable for container planting.

Planting Your Tree in a Large Container

Once you’ve thoughtfully assessed your site, selected an appropriately sized planter, chosen your tree, and acquired a quality potting mix, you’re ready to begin the planting process. This step-by-step guide will walk you through ensuring a healthy start for your container-grown tree.

Materials You Will Need:

• Appropriate Planter or Container: The size should accommodate the mature size of your tree’s root system with room for growth.
• High-Quality Potting Mix: Crucially, use a potting mix specifically formulated for containers, not garden soil, which can compact and impede drainage.
• Slow-Release Fertiliser: This provides a steady supply of nutrients to your tree over an extended period.

Detailed Planting Instructions:

1. Prioritise Drainage: Begin by ensuring your chosen container has adequate drainage holes. Poor drainage is a primary cause of failure in container gardening, as it leads to waterlogged soil. This deprives the roots of essential oxygen and creates an environment conducive to root rot and other soil-borne diseases. If your container lacks sufficient drainage, consider drilling additional holes. You might also consider placing a layer of drainage material, such as gravel or broken pottery shards, at the bottom of very large containers to further enhance drainage, although the necessity of this is sometimes debated among horticulturalists.

2. Fill with Potting Mix: Carefully fill your container with the potting mix. It is important to leave approximately 2-3 inches (around 5-7.5 cm) of space between the top of the soil and the rim of the container. This “headspace” is crucial for allowing water to pool temporarily when you water, ensuring thorough soaking of the soil before it overflows. Using a lightweight potting mix is vital as it is specifically formulated to provide the right balance of aeration and water retention, unlike denser garden soil which can become compacted in a container environment.

3. Position Your Tree: Gently remove your tree from its nursery pot, taking care to minimise disturbance to the root ball. Some trees will have more extensive root systems than others. For larger root balls, you may need to position the tree first and then carefully add the potting mix around it. The critical point here is to ensure that the tree’s stem or trunk flare (the area where the trunk widens at the base) is not buried beneath the soil level. Planting too deeply can lead to stem rot and other detrimental issues for the tree’s health. The top of the root ball should be level with or slightly above the surrounding potting mix in the container.

4. Add Soil and Secure the Tree: Once the tree is positioned correctly, begin adding more potting mix around the root ball. Gently firm the soil as you go to eliminate air pockets, but avoid compacting it too tightly, which can impede root growth. Pay particular attention to filling the spaces around the edges of the root ball. As you fill, ensure that the soil level remains at least 3 cm (approximately 1 inch) below the rim of the pot. This reserved space allows for effective watering without immediate runoff.

5. Incorporate Slow-Release Fertiliser: After planting, evenly sprinkle the recommended amount of slow-release fertiliser onto the surface of the potting mix. Distribute it around the perimeter of the container and on the top layer of the soil, being careful not to place the fertiliser directly on top of the tree’s roots, as this can cause burning. The slow-release granules will gradually release nutrients into the soil each time you water, providing a consistent source of nourishment for your growing tree.

6. Initial Watering: Once planting and fertilising are complete, water the container thoroughly. Apply water slowly and deeply until you see it begin to drain from the bottom of the pot. This initial deep watering helps to settle the soil around the roots and ensures they have access to moisture. Allow the excess water to drain completely.

7. Subsequent Watering: After the initial soaking, avoid watering again for several days. The frequency of subsequent watering will depend on various factors, including the type of tree, the size of the container, the weather conditions (temperature, humidity, wind), and the type of potting mix used. A reliable guideline is to check the moisture level of the soil by inserting your index finger about two knuckles deep into the potting mix. If the soil feels dry at this depth, it’s time to water. Avoid overwatering, which is as detrimental as under-watering. Allow the soil to dry out slightly between waterings to ensure proper aeration of the root zone.

By following these detailed steps, you’ll provide your container-grown tree with a strong foundation for healthy growth and development. Remember to observe your tree regularly for any signs of stress or nutrient deficiencies and adjust your care practices as needed.

Selecting Trees For You Plant Container

Here are 10 types of trees and shrubs that are generally well-suited for growing in containers in many parts of Australia, offering a mix of natives and adaptable non-natives:

Citrus Trees (dwarf varieties): Dwarf varieties of lemons (‘Meyer’), limes, mandarins (‘Imperial’), and kumquats thrive in containers, offering fragrant blossoms and delicious fruit. They need plenty of sun, regular watering, and feeding.

Example: Dwarf Meyer Lemon trees can stay under 2 meters in a container.

Japanese Maples (Acer palmatum dwarf cultivars): With their graceful forms and stunning autumn foliage colours, dwarf Japanese maples make beautiful container specimens. They prefer a sheltered spot with protection from harsh sun and wind.

Example: Acer palmatum ‘Crimson Queen’ is a weeping variety that stays relatively small.

Olive Trees (Olea europaea dwarf or slow-growing varieties): Olive trees are drought-tolerant and have attractive silvery foliage. Dwarf or slow-growing varieties are suitable for containers and can add a Mediterranean feel. Choose a sunny spot and well-drained soil.

Example: Dwarf Olive trees can be maintained at a height of 1.5-2 meters in a pot.

Crepe Myrtles (Lagerstroemia indica dwarf varieties): These deciduous trees offer beautiful summer flowers in various colours and attractive bark in winter. Dwarf varieties like ‘Tonto’ or ‘Zuni’ are well-suited for pots. They prefer a sunny location and regular watering during the growing season.

Example: Dwarf Crepe Myrtles typically grow to around 1.5-3 meters.

Bay Laurel (Laurus nobilis): This evergreen tree has aromatic leaves used in cooking and can be pruned into various shapes, making it ideal for formal container displays. It prefers a sunny to partly shaded position and well-drained soil.

Example: Bay Laurel can be kept to a manageable size of 1-2 meters in a container through pruning.

Australian Native Options:

Dwarf Bottlebrush (Callistemon spp.): Many dwarf varieties like ‘Little John’ or ‘Mini Red’ stay compact and produce their iconic, nectar-rich flower spikes that attract birds. They are hardy and relatively low-maintenance.

Example: Callistemon citrinus ‘Little John’ typically grows to about 1 meter tall and wide.

Dwarf Gums (Corymbia ficifolia dwarf cultivars): These are smaller versions of the iconic Flowering Gums, offering spectacular displays of red, orange, or pink flowers in summer. ‘Baby Orange’ is a popular choice. They need a sunny, well-drained position.

Example: Corymbia ficifolia ‘Baby Orange’ reaches around 2-3 meters in height.

Acacia cognata ‘Limelight’ or ‘Fettuccini’: These wattles have beautiful weeping foliage in shades of lime green or bronze. They are relatively fast-growing but can be kept to a manageable size in a container with occasional pruning. They prefer well-drained soil and a sunny spot.

Example: Acacia cognata ‘Limelight’ grows to about 1 meter high and 2 meters wide.

Banksia ‘Birthday Candles’ or other dwarf Banksias: These smaller Banksias offer unique and attractive flower spikes that attract native wildlife. They prefer well-drained, slightly acidic soil and a sunny location. Use a low-phosphorus fertilizer formulated for natives.

Example: Banksia spinulosa ‘Birthday Candles’ grows to about 0.5 meters high and 1 meter wide.

Rottnest Island Tea Tree (Melaleuca lanceolata ‘Nana’): This is a compact, hardy shrub with attractive foliage and white, fluffy flowers. It’s drought-tolerant once established and can handle coastal conditions.

Example: Melaleuca lanceolata ‘Nana’ typically grows to around 1-1.5 meters tall.

Container Tree Management:

Maintaining trees in containers requires specific techniques distinct from in-ground cultivation.

Watering Protocol:

Watering frequency is adjusted based on the tree’s developmental stage. Initially, water twice weekly. As the tree matures, increase water volume and frequency. A practical indicator for irrigation is soil dryness at a depth of two knuckles when inserting a finger.

For containerised trees in public installations, implement drip irrigation systems to ensure consistent and efficient hydration, reducing manual intervention.

During periods of high ambient temperature, saturate the container until drainage occurs. Subsequently, fill the saucer beneath the container to provide supplemental water uptake throughout the day.

Fertilisation Regimen:

Utilise a potting mix containing slow-release fertiliser at the time of planting. This provides a sustained nutrient supply for approximately two months post-planting.

For public container tree projects, the incorporation of slow-release fertiliser is recommended for reduced maintenance. If not utilized, regular application of liquid fertilizer during irrigation will be necessary.

Adhere strictly to the fertiliser application rates specified by the manufacturer. Exceeding recommended quantities can negatively impact tree health.

Pest and Disease Management:

Regularly inspect foliage and stems for evidence of insect pests or disease. Monitor leaf undersides and stem junctions.

Maintain optimal tree vigour through consistent watering and appropriate fertilisation to enhance natural resistance to pests and diseases. Physical barriers can be employed to deter larger fauna.

Severely affected plant material should be promptly pruned and removed to prevent the spread of infestation or disease to healthy portions of the tree or adjacent plantings.