Lemon Verbena

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a species of semi-woody flowering plants within the Verbenaceae family

 

Lemon verbena is a deciduous sub-shrub, perennial in nature, and native to South America. The plant is well known for its sweet lemon scent, and has numerous recorded and anecdotal culinary, medicinal, and perfumery uses. Below is an overview of its taxonomy, morphology, history, and uses, as well as an overview of the chemistry of its essential oil.

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SYNONYMS & COMMON NAMES

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see notes for full author name

 

A. citrodora has been shuffled between several genera in the Verbena family (Verbenaceae), and to this day several publications still use one of its synonyms, instead of its accepted name. It is most often still lopped into the Lippia genus.

Aloysia triphylla (L'Hér.) Britton | Verbena triphylla L'Hér. | Verbena citrodora L'Hér. | Lippia citriodora (Palàu) Kunth | Lippia triphylla (L'Hér.) Kuntze

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Lemon verbena, Herb(a) Louisa, and lemon beebrush—other plants within the vervain family share the beebrush common name. Also known as verbena. Though the latter is slightly generic, hence it can easily be confused for other plants in the family. In French it's known as verveine, which adds to verbena/vervain confusion.

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Distribution

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Native to South America—more specifically Argentina and Chile. Within a cultivated and semi-wild state it can be found across the Mediterranean region, as well as Kenya and China. Within temperate regions it can easily be picked up at garden centra and nurseries.

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TAXONOMY

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+ Kingdom: Plantae

+ Unranked: Angiosperms

+ Unranked: Eudicots 

+ Unranked: Asterids

+ Order: Lamiales - it contains +/- 24.000 species, several genera—and by extension species—of economical importance belong to it, many of which are known for their scent and taste. Such as: jasmin (Jasminum - several species), lavender (Lavendula - several species), mint (Mentha - several species), basil (Ocimum - several species), rosemary (Rosmarinus officinales), olive (Olea europaea), and several others.

+ Family: Verbenaceae - authored by Jean Henri Jaume Saint-Hilaire. Several genera which previously belonged to the verbena family have been excluded and moved to other families. Plants are reassigned and if needed renamed when new information and links are discovered and analysed. In the past, the renaming and reassigning of plants, aside from new discoveries, often came about over information being lost, botanists who weren't well known, not having access to the right (or weakened) plant materials, etc.

+ GenusAloysia (type species: Aloysia citrodora) - Palàu is credited as the author, since A. citrodora was the first species published to the genus

+ Species: Aloysia citrodora | A. citrodora Palàu. Published in 1784. In its common name the plant is easily confused with vervain (Verbena officinalis).

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MORPHOLOGY

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see botanical terms for definitions on the morphological terms used

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+ Flowers: racemose inflorescence of tiny flowers (see illustration above). The flowers are white or pale lilac in colour.

+ Leaves: between 5 - 10 cm in length, lanceolate in shape, three leaves per node), the leaf blade is attached by a short petiole. The leaf is rather though when fresh, but when it dries, the midrib and petiole curl, and the entire blad becomes rather brittle.

+ Size: between 1m and 3m in width and height—3m at full maturity (which takes five to ten years). 

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Author

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see notes for author summaries

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Authored by Antonio Palàu y Verdera in 1784. Palàu was a Spanish botanist at the Madrid botanical garden. He named the species, as well as the genus (Aloysia), which he named after Maria Luisa of Parma (1751-1819), wife of King Charles IV of Spain. Aloysia is the latinised version of Luisa. Palàu published a description of the plant previously—assumed in collaboration with Casimiro Gómez de Ortega—under the name: 'Los profesores de Botánica en el Real Jardin de esta Corte', though it wasn't considered effectively published, so his official publication of the name is dated to 1784.

Its synonym Aloysia triphylla, formerly Verbena triphylla, was given by Charles Louis L'Héretier de Brutelle in 1786 (possibly late 1785) and later corrected by Nathaniel Lord Britton. Britton kept the specific epithet, but moved it to the right genus, Aloysia. Because the specific epithet did not change, both L'Héretier and Britton are listed as the authors, as such: Aloysia triphylla (L'Hér.) Britton. Verbena is an extant genus, and like Aloysia, it belongs to the Vervain family (Verbenaceae). 

In 'On Aloysia Palàu' published in 1992 (see resources), the authors suggest that the main reason Palàu's work went unnoticed—causing several incorrect renames—was that he was a relatively unknown botanist at the time, published only a single taxon, and that the date 1784 appears on L'Héretier's title page. When L'Héretier published his description he did cite in synonymy 'Aloysia citrodora Casim. Gom. Ort. & Anton.', with the first author abbreviation standing for Ortega (correct citation: Ortega) and the second standing for Antonio—Palàu's first name. Ortega sent live plants specimens of lemon verbena, as well as seeds, to L'Héretier. It appears that L'Héretier's citation references the handwritten copy of the booklet Ortega and Palàu published, and not the official publication of the name.

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SPECIFIC EPITHET

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citrodora, meaning, with a lemon scent, referring to the rich lemon-like scent released by the plant. As a specific epithet, citrodora is invariable—it will not adapt to the gender of genus. 

For its synonym Aloysia triphylla, the specific epithet refers to the external morphological feature of its leaves—arranged in threes. Here the specific epithet follows the gender of the genus, if the genus would've been named Aloysius, then the name would have read Aloysius triphyllus.

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Uses

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essential oil

Extraction: steam distillation | Part of the plant: leaves | Distribution: cultivated plants grown in France and North Africa (Morocco). 

In contrast with the fresh leaves, the essential oil leans more towards a lemon-floral tone, where as the fresh leaves have a more herbaceous-lemon scent. It blends well with citrus based essential oils, including neroli and petitgrain, as well as palmarosa.

High in citral—which is made up of two compounds: geranial and neral—and limonene. If you're wondering why you can't find citral as a compound on a chromatographic analysis of lemon verbena, just look for the geranial and neral percentages and add them up. The exact percentages of the constituents of a plant are dependant on growing factors (soil composition, region, sunlight,etc.) and harvesting times—when dealing with non-specific information (exact region, grow year, etc.) we work with averages. For exact percentages, see notes.

The following constituents—present in lemon verbena essential oil—are known irritants and allergens, and can cause sensitisation in certain individuals—most often dermal irritation: limonene (when oxidised), geranial, geraniolneral, and linalool (occurs naturally in over 200 plants, mainly within the Lamiaceae, Lauraceae, and Rutaceae families, as well as a few others—only a known irritant when oxidised). Citral (geranial + neral) is known to cause phototoxicity—irritation triggered by exposure to sunlight.*

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medicinal

Part of the plant: aerial parts

Lemon verbena is reputed for its antispasmodic (suppresses muscle spasms—in this case abdominal related spasms), antipyretic (fever reducing), sedative, and digestive qualities (see notes). Within folk use, it has been used for asthma, spasms, cold, fever, flatulence, colic, diarrhea, indigestion, insomnia, and anxiety. And, its essential oil—as with most essential oils—has shown antimicrobial properties.

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drink

Part of the plant: aerial parts

Lemon verbena is a popular herbal tea (tisane). It has has a mild lemon, flowery taste—which works well as iced tea. You can use the dried, as well as the fresh leaves to flavour water kefir or kombucha (you'll still need a green tea or a black tea kombucha as a base). The Nordic Food Lab has a blog post up on their experiments with lemon verbena kombucha. It can also be used in alcoholic beverages, either to infuse (lemon verbena infused vodka) (homemade or commercial), or as an addition to cocktails by muddling the leaves. 

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food

Part of the plant: aerial parts

The leaves hold up well to heat, so they can be used in cold, as well as hot preparations. The leaves are rather though, so they're not ideal for direct consumption. They're best used in infusions, or you can remove the leaves before consumption. It pairs up nicely with fish and poultry, as well as many vegetable dishes, and fruits. 

Standard author abbreviations used in this entry: Palàu :  Antonio Palàu y Verdera - Spanish botanist at the Madrid botanical garden - (1734-1793). Ortega : Casimiro Gómez de Ortega - Spanish physician and botanist (1741-1818). L'Hér. : Charles Louis L'Héretier de Brutelle - Spanish botanist and magistrate - (1734 - 1793). Britton : Nathaniel Lord Britton - American botanist and taxonomist - (1859-1943). Kunth : Carl Sigismund Kunth - German botanist - (1788-1850). Kuntze : Otto Kuntze (Carl Ernst Otto Kuntze) - German botanist - (1843-1907). J.St.-Hill. : Jean Henri Jaume Saint-Hilaire - French naturalist and artist - (1772 – 1845).

On priority of names and accepted names: priority means the oldest (correct) published name of a taxon is the accepted name. Aside from a few exceptions, this starts from the publication of Linnaeus's Species Plantarum (1753). Revisions and corrections are made when necessary—when a species was placed in the wrong genus, family, etc. For example: Aloysia triphylla (L'Hér.) Britton: this means L'Héretier originally placed lemon verbena in the wrong genus, namely Verbena (Verbena triphylla), Britton corrected this to Aloysia. But, when it comes to the accepted botanical name of lemon verbena the rule of priority—as with almost any name—applies, meaning Palàu published the name first (1784), since the name is correct, there shouldn't be an argument as to which name is and should be accepted.

This rule is recognised under the International Code of Nomenclature for algae, fungi, and plants (Melbourne Code). Which is reviewed and revised by an International Botanical Congress, the Melbourne Code (2012) is the 18th revision and supersedes all previous codes. As an aside, cultivated plants fall under a different code—International Code of Nomenclature for Cultivated Plants.

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Lemon verbena's primary constituents: Florihana—a french distillery of organic essential oils—has two chromatographic reports up for lemon verbena, one from 2013 and one from 2015, both batches came from plants grown in Morocco. Limonene (20,9% - 23,1%), geranial (13,5% - 12,1%), neral (10,5% - 9,6%)—examples from 2013 given first (rounded to the nearest tenth). Bringing its citral content to 24% in 2013 and 21,7% in 2015.

In an article (see resources) published in The Journal of Ethnopharmacology in 2007, the following percentages were given—the batches tested came from plant material harvested in May (when growth rate is at its maximum) and in September (when the plant is in full bloom): geranial (38,7% - 26,8%), neral (24,5% - 21,8%), limonene (5.8% - 17,7%).

In both batches geranial, neral, and limonene were the primary constituents. Making up 66,3% of the total essential oil yield in May and going up to 69% in September.

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Phototoxicity (photoirritation/photosensitivity): I've personally experienced phototoxicity from citrus based essential oils (used neat) during the summer months. They can itch and burn for up to two weeks, and the actual mark can take up to several months to fade. Easy to avoid by not applying citrus based, as well as citral (lemongrass, etc.) containing, essential oils or blends (neat or diluted) on exposed skin during a sunny day.

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On the medicinal qualities of lemon verbena: I used several scientific papers in my research, one published under 'The Journal of Ethnopharmacology', which is an interdisciplinary journal devoted to indigenous drugs'. One under 'Boletín Latinoamericano y del Caribe de Plantas Medicinales y Aromáticas'. And, another published under the journal of 'Biochemical Systematics and Ecology'. (see resources for exact articles)

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Thank you to Patrick Kelly from Sigil Scent for aiding me with the scent description.

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Below are links to The Hungry Child's internal database on the terms and taxa that were used in this article, or might be useful alongside it. If you feel that something is missing or unclear, leave a comment or send me an email.

genus | epithet | inflorescence 

The following morphological terms don't have articles up yet, so here's a short definition for each.

Racemose: (flower structure) arranged in a raceme structure. Lanceolate: (leaf shape) lance-shaped. Petiole: (leaf structure) the petiole attaches the leaf blade to the main stalk. Aerial parts: parts of the plant that grow above ground.



 

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