Vernonia

Key takeaways

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

Reference excerpt

Vernonia is a genus of about 350 species of forbs and shrubs in the family Asteraceae. Some species of this genus are known as ironweeds. Some species are edible and of economic value. They are known for having intense purple flowers. There have been numerous distinct subgenera and subsections named in this genus, and some botanists have divided the genus into several distinct genera. For instance, the Flora of North America recognizes only about twenty species in Vernonia sensu stricto, seventeen of which are in North America north of Mexico, with the others being found in South America.

Taxonomy The genus was circumscribed by Johann Christian Daniel von Schreber in Gen. Pl. ed. 8[a]. vol.2 on page 541 in 1791. The genus name of Vernonia is in honour of William Vernon (1666/67 – c. 1711), who was an English plant collector, (bryologist) and entomologist from Cambridge University, who collected in Maryland, USA in 1698.

Species

Species of this genus are found in South America, Africa, Southeast Asia, and North America. Vernonia species are well known for hybridizing between similar species in areas of overlapping ranges. There are approximately 350 species in the genus. A selected list is given below.

North America Vernonia acaulis Vernonia arkansana Vernonia angustifolia Vernonia baldwinii Vernonia blodgettii Vernonia fasciculata Vernonia flaccidifolia Vernonia gigantea or Vernonia altissima Vernonia glauca Vernonia larseniae Vernonia lettermannii Vernonia lindheimeri Vernonia marginata Vernonia missurica Vernonia noveboracensis Vernonia proctorii Vernonia pulchella Vernonia texana

South America Vernonia nonoensis Vernonia patens Vernonia scorpioides Vernonia condensata

Africa Vernonia amygdalina Vernonia calvoana Vernonia colorata Vernonia galamensis Vernonia kotschyana Vernonia staehelinoides Vernonia cineria vernonia myriantha

Asia Vernonia andersoni Vernonia arborea Vernonia cockburniana Vernonia elaeagnifolia Vernonia unicata Vernonia zollingerianoides

Uses

Food, medicine and oilseed Several species of Vernonia, including V. calvoana, V. amygdalina, and V. colorata, are eaten as leaf vegetables. Common names for these species include bitterleaf, onugbu in the Igbo language, ewuro and ndole. They are common in most West African and Central African countries. They are one of the most widely consumed leaf vegetables of Nigeria, where the onugbu soup is a local delicacy of the Igbo people, and of Cameroon, where they are a key ingredient of Ndolé: the national dish of Cameroon. The leaves have a sweet and bitter taste. They are sold fresh or dried and are a typical ingredient in egusi soup. Vernonia amygdalina is used in traditional herbal medicine. These leaves are exported from several African countries and can be purchased in grocery stores aiming to serve African clients. In Brazil, V. condensata is commonly known as "figatil" or "necroton" and used in local traditional medicine. Vernonia galamensis is used as an oilseed in East Africa. It is grown in many parts of Ethiopia, especially around the city of Harar, with an average seed yield of 2 to 2.5 t/ha. It is reported that the Ethiopian strains of Vernonia have the highest oil content, up to 41.9% with up to 80% vernolic acid, and is used in paint formulations, coatings plasticizers, and as a reagent for many industrial chemicals.

Horticulture Vernonia are grown as ornamental plants in gardens, particularly some of the larger herbaceous North American species which are favoured for prairie-style plantings. The most widely grown are V. angustifolia, V. arkansana (syn. V. crinita), V. baldwinii, V. fasciculata, V. gigantea (syn. V. altissima), V. lettermannii, V. missurica and V. noveboracensis. A few cultivars have been selected, mostly on the basis of greater size and robustness (e.g. V. angustifolia 'Plum Peachy', V. gigantea 'Jonesboro Giant') or white flower colour (e.g. V. arkansana 'Alba', V. noveboracensis 'Albiflora', V. noveboracensis 'White Lightning').

Ecology

Vernonia species are used as food plants by the larvae of some Lepidoptera species including Coleophora vernoniaeella (which feeds exclusively on the genus) and Schinia regia (which feeds exclusively on V. texana). Vernonia is a very diverse genus, varying from the tiny V. desertorum of the Caatinga region of Brazil which is only 8 cm (3.1 in) tall to Vernonia arborea of the East Indies which, at 36 m (118 ft) is the tallest of all composites; a 472 fold difference in height. The liana Vernonia andersoni of Burma, according to Menninger, "climbs into the tops of trees" and could be even taller. The leaves can vary from quite small up to 1.2 m (3 ft 11 in) long by up to 38 cm (15 in) in width in the case of Vernonia conferta of Cameroon.

References

Illustrations

Worked examples

Example 1 — a first encounter with Vernonia

Start with the simplest possible case. Write down what Vernonia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Vernonia 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 Vernonia 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 Vernonia

In research: Vernonia appears in biology 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 Vernonia 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: Vernonia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Asteraceae genera, Butterfly food plants, Vernonia, so understanding it makes those chapters shorter.
In everyday life: Look for Vernonia 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.

How to study Vernonia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vernonia 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 Vernonia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vernonia in simple terms?

Vernonia is a genus of about 350 species of forbs and shrubs in the family Asteraceae. Some species of this genus are known as ironweeds.

Why does Vernonia matter?

Because it connects several biology 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 Vernonia?

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 Vernonia.