Banksia serrata

Banksia serrata is part of a group of bushes or small trees native to the southern regions and related to proteas. This botanical species is characterized by a twisted trunk, a columnar habit, and a layered branch structure adorned with narrow, glossy leaves that are strongly dentate along the edges. Its summer flowering, typical of Banksias, takes the form of cylindrical spikes ranging in colour from yellow to grey with silvery highlights. Native to the Australian east coast, this Banksia is a frost-sensitive plant that thrives in coastal conditions and only flourishes in well-drained, acidic to neutral soils that are low in phosphorus and preferably sandy. Outside of the most favourable coastal areas, it can be cultivated as an indoor plant.

Banksia serrata belongs to the proteaceae family, just like the Grevillea and the Protea. It is native to the eastern coast of Australia, specifically the states of Victoria and Queensland, as well as Tasmania. It is almost exclusively found in coastal dunes, in sandy, acidic, poor, and well-drained soils. Its hardiness does not exceed -4°C as a mature subject. This evergreen bush or small tree, with a rather fast growth rate, generally exhibits a narrowly ovate crown carried by a short, twisted trunk covered in a grey and rough bark. Banksia serrata can reach an average height of 9m (29ft 6in) with a spread of 3m, depending on the growing conditions. Its branches bear entire, leathery leaves with a shiny medium green colour on the upper side, lighter on the underside, arranged in whorls. These leaves are long and narrow, with a serrated margin.

The flowering of the Banksia serrata usually takes place in June and July. The inflorescences emerge from nodes aged two to three years and are 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 woody, central axis of the spike. The flowers are pollinated by insects and give rise to hard fruits in the shape of beaks. Like most Banksia species, the Banksia serrata needs the heat of fire to release its fruits and disperse its seeds.

Banksia serrata is an exotic plant whose cultivation is somewhat difficult, as is the case with many proteaceae. It can be grown in coastal gardens without heavy frosts. Particularly suitable for the Mediterranean coast, it tolerates summer drought well and looks good when grown as a specimen, hedge, or in the background of flower beds. In an exotic garden, it can be associated with the Canary Island Viper's Bugloss, Puyas, Euphorbia characias, Honey Spurge, Giant Fennel, Leucadendron, Melianthus major, Melaleuca gibbosa, Acacia karoo (Mimosa), palm trees, or grevilleas. It adapts well to container cultivation which allows control over the growing medium and easy winter storage.

A unique root system adapted to poor and dry soils:

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