Iruni Kalupahana Jadetimes Staff
I. Kalupahana is a Jadetimes news reporter covering Australia
Introduction
Banksia is a varied and peculiar plant genus indigenous to Australia with 173 described species, of which all but one occur naturally exclusively within the country. The genus honors British botanist Sir Joseph Banks, who first gathered them in 1770 aboard Captain James Cook's expedition to Australia. Banksia are identified by their exceptional flowers and ecological value. In recent times, genus Dryandra, with around 90 species, has been added to Banksia based on botanical studies that established their close genetic relationship. There have also been Banksia cultivars developed to be planted as ornamental plants, with some of them hybridized to produce larger flowers, greater hardiness, and to be able to thrive in different climates. Banksia is from the Proteaceae family, to which Grevilleas, Waratahs, and Macadamias also belong, a reflection of its long evolutionary past in Australian flora.
Natural Distribution
Banksias are distributed across parts of Australia, and the southwestern parts have the most diversity with 60 documented species. Southwest Australia's Mediterranean climate, where there are wet winters and hot summers, has provided an ideal niche for Banksia to evolve into many special species. Banksias are also a dominant part of the vegetation on the eastern coast, forming important ecosystems in heath and woodland. Few species have developed to rainforests or dry climates, as Banksias prefer well-drained soils and moderate moisture. Amazingly, Banksia dentata, or the Tropical Banksia, is the only species found in both eastern and western Australia, extending as far as Papua New Guinea, Irian Jaya, and the Aru Islands. This species is unique because it thrives in monsoonal climates, tolerating seasonal flooding, unlike other Banksia species that prefer drier conditions.
Flowers and Seed Formation
Banksia's distinctive flower heads consist of hundreds or thousands of small flowers in pairs, which are colored from yellow to red. Every one of these small flowers produces a great amount of nectar, and Banksia is therefore an important source of food for Australian native wildlife, such as honeyeaters, possums, and even some bats. Many species bloom autumn and winter and provide nectar when other species are not flowering, vital to the pollinator's survival over these periods. The inflorescence of flowers varies across species; Banksia grandis consists of great cylindrical spikes of flowers, whereas Banksia spinulosa produces dense, little flowers. The fruits of Banksia, or follicles, are hard and woody and are cone shaped in appearance though not conifer cones as coniferous trees produce. These follicles also serve to protect the seeds from browsing animals and harsh climatic conditions. All Banksia species have developed mechanisms to withstand fire-prone environments, where the follicles will only open in response to hot temperatures. This process provides a means by which seeds fall onto fertile ash covered soil after a fire, thus improving successful regrowth.
Propagation and Growth Requirements
Banksias are easily propagated from seed, and one of the most popular methods is to heat cones in an oven at 120°–140°C for around an hour to cause seeds to be released. Insect infestations in flower buds, however, can kill developing seeds and prevent germination. One of the most widespread pests is the Banksia Seed Moth (Xylorycta strigata), which lays eggs on flower buds, and whose larvae consume seeds in follicles before they are mature. Seeds like well draining soil and must be treated gently to avoid fungal disease like Phytophthora cinnamomi, a root rot fungus that attacks a broad range of native Australian species. To minimize the risk, growers often sterilize the seed raising mix before sowing or use a fungicide treatment. Transplanting must be performed after the first true leaves have appeared, in a river sand, loam, and organic matter such as leaf mold or peat moss potting mixture. Banksia species being resilient, there are some that occur natively in Western Australia, such as Banksia cuneata, which may not do well in moist environments due to the fact that they occur natively in arid places and are susceptible to fungal infections.
Popular Garden Varieties
Several Banksia species are cultivated widely for their usefulness, durability, and wildlife value. Banksia integrifolia (Coast Banksia) is ideal for coast areas, being tolerant to salt spray, frost, and high winds, and serves as an effective windbreak plant. Banksia ericifolia (Heath Banksia) is ideal for screening, having orange-red flowers that last for months, and is a favored native garden plant. Banksia serrata (Saw Banksia) is coarse and serrated of bark, with leaves and dramatic landscaping value. It is a lignotuber forming one of the Banksias, a woody subterranean growth that allows it to resprout from a bushfire. Banksia marginata or Silver Banksia is highly tolerant and will flourish in almost any environment, ranging from beach dunes to hills, and therefore one of the most tolerant Banksia species. Hybrid types such as Banksia 'Giant Candles' have spectacular floral displays with floral spikes reaching a length of 40 cm that are among favorite plants with Australian native gardeners. Some Banksias are also cultivated as bonsai, with their curved trunks and unique leaves creating a beautiful scene in their diminutive state.
Banksias remain a crucial part of the ecosystems in Australia, providing sustenance and refuge for animals as well as providing materials for researchers who study plant adaptation and fire hardness. Natural in the wild or thriving in home gardens, these amazing plants remain Australia's botanical symbol.
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