Banksia

Growing Guide

🌞 Full sun

💧 Drought tolerant

🌺 Flowers late winter to summer

✂️ Prune after flowering

🐞 Pest-resistant

🌿 Well-drained soil

🔥 Fire-adapted species

Banksia are a diverse genus that are well-known for their cylindrical flower spikes and woody cones.

There are over 170 species of this native, which thrive in a range of environments, from coastal dunes to mountainous regions, showcasing an adaptability and resilience in the Australian landscape.

While the name Banksia honours botanist Sir Joseph Banks, who first collected specimens during Captain James Cook's voyage to Australia in 1770, fossil records reveal that these plants in fact date back over 50 million years, making them a significant part of the nation's natural history.

Banksias show remarkable diversity across Australia, with distinct differences between those found in Western Australia and those on the eastern seaboard.

Western Australian Banksias are adapted to the region's nutrient-poor, sandy soils and hot, dry climate. They often feature striking, brightly coloured flower spikes and intricate foliage. In contrast, Eastern Australian Banksias, like Banksia serrata and Banksia integrifolia, are commonly found in coastal and woodland areas with more fertile soils and higher rainfall.

These species tend to have larger, more robust leaves and flower spikes that are generally less colourful but equally impressive. The regional adaptations highlight the resilience and versatility of Banksias, showcasing their ability to thrive in diverse environmental conditions across the continent.

Soil

Banksias indigenous to the eastern states of Australia thrive best in well-drained, slightly acidic soils with a pH between 5.0 and 6.5.
Banksias do not tolerate waterlogged conditions, which can lead to root rot. Ensure the soil drains well by incorporating sandy loam or gravelly materials. Raised beds can be an excellent option to improve drainage, especially in areas prone to heavy rainfall.
To improve clay soil, consider using raised beds filled with sandy loam and incorporate organic matter, compost, coarse sand or grit to enhance drainage. Adding gypsum can also help break down clay particles and improve soil structure.
Applying organic mulch, such as bark, wood chips, or leaves, around your Protea helps retain moisture, reduce weeds, and maintain consistent soil temperature. As the mulch decomposes, it adds nutrients to the soil.
Ensure the mulch is kept a few centimetres away from the stems to prevent rot and fungal infections.
Maintaining the right pH level is crucial. If your soil is too alkaline, consider adding sulfur or iron sulfate to lower the pH. Regularly test your soil’s pH and adjust as necessary to keep it within the optimal range.
Western Australian Banksias are particularly sensitive to phosphorus. Use a native plant potting mix with low phosphorus levels, or amend your soil with low-phosphorus fertilisers specifically formulated for Australian natives.

Sun

Banksia prefer a location with full sun and don't perform well in dense shade. Planting in areas with limited sunlight will result in poor growth, reduced flowering and increased susceptibility to pests and diseases.
Full sun requires a minimum of six hours of direct sunlight each day.
This is essential for protea to develop vibrant colours and a strong structure.
Full sun also promotes efficient photosynthesis, leading to healthier and more vigorous growth.
A north-facing spot in your garden will receive the most sunlight throughout the day. You can use the compass app on your smartphone to find the best north-facing location.

Planting

When: The best times to plant protea are in autumn or early spring. These seasons allow the plants to establish roots before the intense heat of summer or the cold of winter. If planting in summer, monitor your plant closely to ensure it doesn't dry out.
Give it a drink: To minimise transplant shock, water your plant about 30 minutes before planting. Turn your hose on low and fill the pot with water until it reaches the rim. Allow the water to drain completely, then repeat this process two more times. This ensures the soil is thoroughly moistened and allows the roots to absorb water before planting.
Dig the hole: Dig a hole twice the width and the same depth as the root ball. This gives the roots ample space to spread and grow.
Backfill: Use either the excavated soil or a quality native potting mix with low phosphorus content to fill around your plant. Gently firm the soil around the roots to remove air pockets.
Water it thoroughly: After planting, give it another good drink to settle the soil around the roots. You can also use a seaweed solution such as Seasol or Charlie Carp to reduce plant stress and encourage root growth.
Mulch: Spread a layer of mulch about 5-10 cm thick around the base of the plant, but keep it a few centimetres away from the stem to prevent rot and fungal issues. Regularly replenishing the mulch ensures continued benefits and supports the overall well-being of your plants.

Watering

When you first plant your Banksia, water it thoroughly to help establish strong roots. This means soaking the soil around the root ball to ensure the water reaches deep into the soil.
For the first few weeks after planting, check the soil moisture regularly. If the top 5-10 cm of soil feels dry, water the plant again. During this establishing period, consistent moisture is key, but the soil should be allowed to dry out slightly between waterings to prevent root rot.
Once established, usually after a few months, Banksias become quite drought-tolerant and need minimal watering.
Water deeply but infrequently. Generally, this means watering about once a week during dry spells. In cooler or rainy periods, you may not need to water at all. Ensure the water penetrates deeply into the soil to encourage deep root growth. Shallow watering can lead to weaker roots and less drought tolerance.
During hot, dry weather, you might need to water more frequently. In cooler or rainy periods, reduce watering.
Watch for signs of stress such as wilting or drooping leaves. These can indicate the plant needs water. Conversely, yellowing leaves may suggest overwatering or poor drainage.

Shapes, sizes and forms

Banksias display a remarkable diversity in shapes, sizes and forms, making them versatile additions to various garden landscapes.
They vary from dense, bushy shrubs to upright, spreading trees, each with unique foliage and striking cylindrical or spherical flower spikes.
Small shrub species grow between one to three metres tall and are perfect for compact spaces and container planting.
Medium-sized shrubs and small trees, typically reach heights of three to seven metres, providing excellent structural elements and focal points in garden beds.
Large tree species can soar up to 12 metres or more, making them suitable for parks and expansive gardens.

How a banksia grows

Annual growth cycle: Banksias have a distinctive annual growth cycle. Each year, new growth emerges from the tips of their stems, marked by lighter, softer foliage compared to the older, woody growth. This new growth continues throughout the growing season until the plant focuses its energy on producing flowers.
Flowering: Banksias generally bloom from late winter to early summer, although the exact timing can vary depending on the species and local climate. The flowers develop at the ends of the stems and can last for several weeks to months. Banksia flowers are composed of numerous small florets arranged in a cylindrical or spherical shape, creating a striking and unique appearance.
Seed development: After the flowering period, the spent flowers form woody cones that contain seeds. These cones are often retained on the plant for many years. In some species, the seeds are released after exposure to fire, in others, seeds are released naturally over time or when the cones dry out.
Root system: Banksias develop a deep and extensive root system, which helps them access water and nutrients from deeper soil layers. This root system also contributes to their drought tolerance once established. However, it makes them sensitive to poor drainage and waterlogged conditions, which can lead to root rot.
Adaptations to fire: Many Banksia species have evolved to thrive in fire-prone habitats. They possess lignotubers (swollen underground stems) or thick, woody cones that protect seeds during fires. After a fire, these seeds are released into the nutrient-rich ash, promoting new growth and regeneration.

Pruning and maintenance

Proper pruning and maintenance are essential to keep your Banksia healthy, well-shaped and productive. Here’s a general pruning guide:

To encourage a bushier habit, start tip pruning your Banksias when they are young. Regularly pinch or cut back the growing tips of the plant in their first few years. This practice stimulates the growth of multiple branches, leading to a fuller, more compact shape in the long term.
For established banksias, the best time to prune is immediately after flowering. This timing allows the plant to recover and put energy into new growth before the next flowering season.
Avoid pruning during the active growing season or just before flowering, as this can disrupt the plant's natural cycle and reduce flower production.
Prune back into the previous year’s growth, leaving about 10-15 cm of healthy stem with leaves. This encourages the plant to fill out and develop a bushier shape rather than growing too tall and leggy.
Avoid cutting directly under the flower as this can cause new shoots to grow from the top point, making the plant taller and untidy. Instead, prune as described above to maintain a compact, well-shaped plant.

Other important things to know

Avoid high-phosphorus fertilisers such as manure, blood and bone, as Banksia are sensitive to phosphorus. It's also crucial not to plant them in garden beds where these fertilisers have been previously applied.
Do not use mushroom compost as it contains high salt levels, which can lead to nutrient imbalances and damage sensitive root systems.
Banksias are excellent for attracting wildlife to your garden. Their flowers provide nectar for birds, bees and small mammals, while their seeds are a food source for parrots among others.
Banksias can be successfully grown in pots, and some even as bonsai specimens, making them a versatile option for patios, balconies and small gardens. Ensure the pots have excellent drainage and use a native plant potting mix with low phosphorus content.
They typically take three to 10 years to reach full height under optimal conditions and can live for several decades.