earth science

Hakea petiolaris

Hakea petiolaris is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hakea petiolaris rather than just read about it. In short: Hakea petiolaris, commonly known as the sea-urchin hakea, is a shrub or small tree with cream-coloured and pink or purple flowers and woody fruit. It is endemic to the south west of Australia, occurring at the coastal plain, jarrah forest and wheatbelt regions, often at the ancient granite outcrops of Western Australia.

Key takeaways

Hakea petiolaris belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hakea petiolaris to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hakea petiolaris from memory before moving on to harder problems.

Reference excerpt

Hakea petiolaris, commonly known as the sea-urchin hakea, is a shrub or small tree with cream-coloured and pink or purple flowers and woody fruit. It is endemic to the south west of Australia, occurring at the coastal plain, jarrah forest and wheatbelt regions, often at the ancient granite outcrops of Western Australia.

Description Hakea petiolaris grows as an erect shrub or tree up to 9 m (30 ft) in height. The leaves have a distinctive pale-grey colour and are 5.5–15 cm (2–6 in) long and 2.5–6 cm (1–2 in) wide. The flowers are arranged in groups that appear on small branches or in the forks of branches. The groups are roughly spherical and contain 120 to 200 individual flowers. Each flower is 1.4–1.8 cm (0.6–0.7 in) long and white or cream in colour with the perianth (the non-reproductive part of the flower) ranging in colour from pink to purple. Flowering is followed by woody seed capsules which are 2–3.5 cm (0.8–1 in) long and 1–2 cm (0.4–0.8 in) wide. Each capsule splits into valves and releases 2 dark brown or black winged seeds.

Taxonomy Hakea petiolaris was first described by Carl Meissner in 1845, using a collection made at York by Ludwig Preiss. The specific epithet (petiolaris) is derived from the Latin word petiolus meaning "small, slender stalk". The Latin epithet petiolaris refers to the leaves presentation on conspicuous stalks. There are three subspecies, differing in the sizes of their leaves and the colour of the perianth as it ages.

Hakea petiolaris Meisn. subsp. petiolaris has flowers that darken to mauve and then pink and has smaller leaves than those of the other subspecies. It is a shrub or small tree, one to two metres high, possesses a lignotuber and flowers in June. Hakea petiolaris subsp. trichophylla Haegi flowers darken to mauve and then maroon. It is a large shrub or tree, greater than three metres in height and sometimes attaining nine metres. It releases seed stored in its capsules rather than regenerating from a lignotuber in response to fire and flowers from April to June. The hairs on the leaves, that shine grey-green during flowering, are persistent; this is referred to in the epithet trichophylla, that is derived, according to Haegi from the Greek trichos (θρίξ, gen. τριχός; 'hair') and phyllon (φύλλον; 'leaf'). Hakea petiolaris subsp. angusta Haegi which has flowers that darken to mauve and then pinkish mauve. A shrub or small tree, 1–2 m high, it flowers from March to May. The epithet angusta is a Latin word meaning "narrow".

Distribution and habitat Subspecies petiolaris grows in jarrah forest, usually near granite outcrops between the Darling Range and York in the Avon Wheatbelt, Jarrah Forest and Swan Coastal Plain biogeographic regions. Subspecies trichophylla grows near granite outcrops in shrubland near Wongan Hills and with disjunct populations near Kununoppin and Tuttanning Nature Reserve east of Pingelly in the Avon Wheatbelt, Jarrah Forest and Mallee biogeographic regions. Subspecies angusta is only known from a few small populations growing around granite outcrops near Pingaring in the Mallee biogeographic region.

Conservation All three subspecies of H. petiolaris are listed as "not threatened" by the Western Australian Government Department of Parks and Wildlife.

Cultivation

The species is propagated from seed, establishing itself as a large shrub, or a tree to around ten metres, the width is around two metres. The horticultural applications include use as a screening plant or hedge, or displayed as individual specimens. It is a fast growing and hardy species, frost resistant, bird attracting and has good potential as a feature plant. Hakea petiolaris is recommended for the attractive appearance of its flowers and attraction for birds. Clusters of dullish red flowers, contrasted by white styles, are presented at the leaf axis in the austral autumn or winter. The plant is successfully grown in the urbanised sub-coastal regions of southern Australia. The most common subspecies in cultivation is H. petiolaris subsp. trichophylla.

Ecology The presentation of flowers at the stem (cauliflory) may be a relictual characteristic of a time when tall forest dominated the region and pollinators such as birds moved within the dense leaf canopy of under-storey species.

References

Further reading Young, Jennifer (2000) Hakeas of Western Australia : botanical districts of Irwin and Darling - the Northern Sandplains and the South-west Forest West Perth, W.A.. ISBN 0958577803 Media related to Hakea petiolaris at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Hakea petiolaris

Start with the simplest possible case. Write down what Hakea petiolaris claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hakea petiolaris before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hakea petiolaris ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hakea petiolaris

In research: Hakea petiolaris appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hakea petiolaris in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hakea petiolaris is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hakea, Plants described in 1856, Proteales of Australia, so understanding it makes those chapters shorter.
In everyday life: Look for Hakea petiolaris outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hakea petiolaris in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hakea petiolaris means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hakea petiolaris out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hakea petiolaris in simple terms?

Why does Hakea petiolaris matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hakea petiolaris?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hakea petiolaris.