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Physostegia virginiana

Physostegia virginiana is a biology 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 Physostegia virginiana rather than just read about it. In short: Physostegia virginiana, the obedient plant, obedience or false dragonhead, is a species of flowering plant in the mint family, Lamiaceae. It is native to North America, where it is distributed from eastern Canada to northern Mexico.

Physostegia virginiana — main illustration
Physostegia virginiana — illustration

Key takeaways

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

Reference excerpt

Physostegia virginiana, the obedient plant, obedience or false dragonhead, is a species of flowering plant in the mint family, Lamiaceae. It is native to North America, where it is distributed from eastern Canada to northern Mexico. Physostegia are known commonly as obedient plants because a flower pushed to one side will often stay in that position. The name “false dragonhead” refers to the dragonheads of the related Dracocephalum, a genus to which the plant once belonged.

Description It is a rhizomatous herbaceous perennial producing clumps of stiff, squared stems 2–4 ft (0.61–1.22 m) tall. The leaves are lanceolate and toothed. The inflorescence is a long, dense raceme containing many tubular pink flowers which resemble snapdragons. The open fruit is shaped like a vase and contains four triangular, black seeds.

Taxonomy There are two recognized subspecies. They are:

Physostegia virginiana ssp. praemorsa - Widespread further south, to Texas and New Mexico. It has larger flowers, with sterile bracts below the inflorescence, and lacks rhizomes. It is typically found in dry upland sites such as prairies and glades. Physostegia virginiana ssp. virginiana - Found further north and west. It has smaller flowers that lack sterile bracts. It is patch-forming from rhizomes. It is typically found in wetter habitats, such as streambanks and bottomlands. Cultivars of P. virginiana often do not fit well into either of the two varieties and are intermediate in characters. They are thought to have originated from hybridization between the two subspecies.

Cultivation

It is considered a good plant for adding late-season flowers to a garden. Fertile soils produce robust growth and wide spreading, and the plant may require staking. When it grows tall it has a "tendency toward floppiness" that can be controlled with pruning. It can be aggressive and dominate a landscape.

Cultivars Several cultivars have been bred for color variety. Some (agm) have earned the Royal Horticultural Society's Award of Garden Merit. Cultivars include.

'Alba' - white flowers. 'Crown of Snow' - white flowers 'Pink Bouquet' - rose pink flowers 'Rosea' - pink flowers 'Rosy Spire' - lavender-pink flowers 'Summer Snow' (agm) - pure white flowers 'Variegata' - pink flowers, green and white variegated leaves 'Vivid' (agm) - bright pink flowers

References

External links Physostegia virginiana (L.) Benth. ITIS. Physostegia virginiana. Floridata.

Illustrations

Physostegia virginiana illustration
Physostegia virginiana illustration
Physostegia virginiana: Subspecies virginiana has a smaller flower that lacks sterile bracts
Subspecies virginiana has a smaller flower that lacks sterile bracts
Physostegia virginiana: Seeds of Physostegia
Seeds of Physostegia

Worked examples

Example 1 — a first encounter with Physostegia virginiana

Start with the simplest possible case. Write down what Physostegia virginiana 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 Physostegia virginiana 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 Physostegia virginiana 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 Physostegia virginiana

In research
Physostegia virginiana 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 Physostegia virginiana 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
Physostegia virginiana is common in secondary-school and first-year university syllabi. It links to neighbouring topics Flora of Northern America, NatureServe secure species, Perennial plants, so understanding it makes those chapters shorter.
In everyday life
Look for Physostegia virginiana 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 Physostegia virginiana in 20 minutes

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

Frequently asked questions

What is Physostegia virginiana in simple terms?

Physostegia virginiana, the obedient plant, obedience or false dragonhead, is a species of flowering plant in the mint family, Lamiaceae. It is native to North America, where it is distributed from eastern Canada to northern Mexico.

Why does Physostegia virginiana 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 Physostegia virginiana?

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 Physostegia virginiana.

Tags

  • Flora of Northern America
  • NatureServe secure species
  • Perennial plants
  • Physostegia

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