Banksia integrifolia

Banksia integrifolia, commonly known as the Coastal Banksia in its native lands, is a large Australian cousin of the proteas. Its most remarkable characteristic is perhaps its great ability to adapt to its environment. With many different stages, it forms a large, compact bush in extreme growing conditions, but will become a small tree in sheltered situations. Its spring flowering can extend more or less throughout the year in very mild climates. It is composed of soft yellow inflorescences in large cylindrical spikes, resembling candles with evergreen foliage. It is a bush for mild climates that is as unique as it is robust: it is valuable for dry gardens or coastal areas where it can be a magnificent specimen or an astonishing windbreak hedge. You can cultivate it in a container on the terrace, to be stored in winter.

The Banksia integrifolia belongs to the proteaceae family, just like Grevillea and Protea. It is native to the eastern coast of Australia, specifically the states of Victoria and Queensland. It can be found in coastal dunes as well as mountains. This Banksia naturally grows on sandy, acidic, leached, and well-drained soils, but it adapts well to clay or poor and chalky soils. Its appearance and form vary greatly depending on its habitat. On the Australian east coast, it has been extensively used to colonise the local bush and stabilize the dunes.

This evergreen shrub or small tree, with a variable bushy habit and rather fast growth, generally has an oval crown carried by a short and twisted trunk covered with grey, rough bark. The Banksia integrifolia will reach an average height of 7m (23ft) with a spread of 4m (13ft), depending on growing conditions. Its branches bear entire, leathery leaves which are dark green on the upper surface and silver-white on the underside. They are arranged in whorls of 3 to 5 and measure from 4 to 20cm (1.6 to 7.9in) long and 6mm (0.2in) to 3.5cm (1.4in) wide. In the juvenile stage, the leaves are different: their edges are toothed and their size is larger than that of adult leaves.

Flowering generally occurs from March to June. But can extend from February to early May in warm climates. It is not uncommon for the bush to sporadically flower outside of these periods. The inflorescences are born on nodes that are two to three years old, often nestled in the foliage. They are terminal, cylindrical, and erect spikes, 10 to 12cm (3.9 to 4.7in) tall and 5cm (2in) wide, composed of several hundred tubular flowers spirally arranged around the central, woody axis of the spike. The insect-pollinated flowers give rise to hard fruits in the shape of beaks. Unlike most Banksia species, the Banksia integrifolia does not need the heat from fire to release its fruits and seeds. They are released at the end of summer by mature fruits.

Banksia integrifolia is a rather sensational plant. Despite its lack of hardiness, this shrub is easy to grow in any soil without excess moisture. It will prefer a coastal garden spared from severe frosts, in light, rather poor soil without excess limestone. Particularly adapted to the Mediterranean climate, it tolerates summer drought well and will look good when planted alone, as a hedge, or in the back of dry garden beds, always in an exposed position. In an exotic garden, it can be associated with the Canary or Madeira Viper's Bugloss, Puya, Euphorbia characias, Euphorbia mellifera, Giant Fennel, Leucadendron, Melianthus major, Melaleuca gibbosa, Acacia karoo (Mimosa), palm trees (Trachicarpus fortunei, Sabal minor), or even Grevilleas. It adapts well to container cultivation, allowing it to be stored in winter.

An original root system, adapted to poor and dry soils:

Plants that grow in nutrient-poor soils often form a symbiosis with soil fungi that promote water and nutrient absorption. But the Proteaceae have chosen a different strategy: they develop a large number of specialized lateral roots along their main roots. These roots are called proteoid roots and are induced by rain; they develop under the layer of dead leaves that cover the base of the plant. Rain promotes the decomposition of the leaves, resulting in the release of nutrients. These ephemeral roots generally dry up at the end of the growing season. They have twice the water and nutrient absorption activity of "normal" roots.