Banksia attenuata

Banksia attenuata: The Candlestick Banksia

Imagine a plant that can grow up to 10 meters high, but often forms shrubs in drier areas—this is the Banksia attenuata, also known as the candlestick banksia. It’s not just any plant; it’s a fascinating species with unique characteristics and a rich history.

Physical Characteristics

How does this plant look? With long, narrow leaves and bright yellow inflorescences that appear in spring and summer, the candlestick banksia is a sight to behold. The flower spikes age to grey and swell with the development of woody follicles, creating a striking contrast against its green foliage.

The plant can be approximately 6 inches long and 0.2-0.6 inches wide, with v- or u-shaped serrations on its leaf margins. New growth occurs in late spring and summer, with brilliant yellow inflorescences that are up to 11.8 inches tall and made up of small individual flowers.

The inflorescences have a unique anthesis process where multiple spikes develop over several weeks. The flowers are bright green in bud stage, turn brown and grey as they age, and produce dark furry oval follicles after flowering. Each follicle contains 2 seeds per cone, developing and maturing over seven to eight months from February to December.

Taxonomy

When was the candlestick banksia first discovered? It was first collected by Robert Brown in December 1801 and published in 1810. The specific epithet is Latin for ‘narrowed,’ referring to the leaves narrowing towards the base.

The relationships of Banksia attenuata within the genus are unclear, with various taxonomic arrangements over time. In 1981, George published a revised arrangement that placed B. attenuata in subgenus Banksia, section Banksia, and series Cyrtostylis.

The species is now considered to be part of an extensive clade within the genus Banksia, with its exact relationships still under investigation by ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae.

Geographical Distribution

Where can you find this remarkable plant? The candlestick banksia occurs across southwest Western Australia, including Kalbarri National Park, Murchison River, and the southern edge of the state. It forms an important component of open Eucalyptus woodland as a dominant or understory tree or tall shrub.

The species is restricted to sandy soils, including white, yellow, or brown sands, and sand over either laterite or limestone. Within open woodland alongside various plant species in southwest Western Australia, Banksia attenuata is found in areas with annual rainfall ranging from 300 to 900 mm.

It is adapted to frequent bushfires and can survive through fire by resprouting from lignotubers or epicormic buds. The species is moderately serotinous, releasing seeds after successive autumn rains rather than immediately following a fire.

Biodiversity and Ecological Significance

What role does this plant play in the ecosystem? Banksia attenuata coexists with other species due to variability in fire timing, which allows for competition at longer intervals. Its seeds have a high rate of long-distance dispersal, likely aided by birds such as the black cockatoo and honey possum, which feed on its cones and extract larvae.

The plant is an obligate outcrosser, requiring pollinators to fertilize inflorescences. Invertebrates, including bees, ants, and dragonflies, also play a role in pollination. Research has shown that possums have trichromatic vision, helping them distinguish between certain plants, particularly Banksia attenuata flowers and spikes.

17 slime mold species were isolated from Banksia attenuata bark, adding to the plant’s ecological complexity. The species is also important for its role in nutrient extraction through proteoid or cluster roots, which change depending on the age of the roots.

Cultural Significance and Uses

How has this plant influenced human culture? Aboriginal people made a sweet drink by placing the flower spike in water. Banksia attenuata may have inspired May Gibbs’ Big Bad Banksia Men, and artist Marianne North painted B. attenuata during her stay in Australia in 1880-1881.

The flower spike is used in the cut flower industry, primarily in Western Australia. It’s a symbol of resilience and beauty, often found in gardens and landscapes across its native range.

Conservation and Challenges

What challenges does this plant face? Banksia attenuata requires good drainage, sandy soil, and sunny position, with pH between 5.5 and 7.0. It is sensitive to dieback and humid climates, making it challenging to cultivate in areas outside its natural range.

Research has identified that the species can be affected by diseases such as Phytophthora cinnamomi dieback, which causes yellowing leaves and lesions. Injecting phosphite into affected trees can delay morbidity for five years, reducing the rate of spread. Benzoic acid drenching significantly reduced P. cinnamomi lesion size.

There has been little success with grafting methods for improving adaptability in humid climates, making conservation efforts crucial to protect this unique species.

In conclusion, the candlestick banksia is a remarkable species with a rich history and significant ecological importance. Its unique characteristics and adaptability make it a fascinating subject for both scientific study and cultural appreciation. As we continue to learn more about this plant, its role in the ecosystem becomes even clearer, highlighting the interconnectedness of all living things.