Plant families & knowing your essential oils

Ever get confused by all the latin names, chemotypes, chemovars etc when choosing your essential oils? In the following article I will try to demystify plant names so you know exactly what you’re getting in your bottles of oil!

Plant families and essential oils

Family is a single word with lots of different meanings, for example, it may mean ‘a group consisting of two parents and their children living together as a unit’, ‘all the descendants of a common ancestor’ or even ‘a group of related things’ (1).  It is interesting to note that plants also belong to families, for example, each individual plant belongs to a species; similar species are linked into a genus, and similar genera (plural of genus) are linked into families. Plant families include Apiaceae (formerly Umbelliferae) or Celery or Carrot Family, Asteraceae (formerly Compositae) or Daisy Family, Brassicaceae (formerly Cruciferae) or Cabbage Family, Geraniaceae or Geranium Family, Lamiaceae (formerly Labiatae) or Mint or Nettle Family, Rosaceae or Rose Family (2).  The plant kingdom is vast, with literally hundreds of thousands of different species, over 17,000 plant genera and 642 plant families (4). The Rosaceae (rose) family for instance includes 4828 known species in 91 genera (5).

Essential oils and botanical names

Whilst we often refer to an essential oil’s common name, e.g. Cedarwood, it is extremely important to take note of the latin or botanical name when choosing our essential oils. This is because plants sharing the same common name don’t always possess the same therapeutic properties, uses or contraindications. This is because they may belong to completely different plant families and genera. For example Atlas Cedarwood belongs to the Cedrus genus of the Pinaceae family, whilst Virginian Cedarwood belongs to the Juniperus genus of the Cupressaceae family. 

To avoid confusion ‘botanical nomenclature’ is used which allocates a unique latin name to each individual plant, so that no two plants share the same botanical name. The botanical name has two parts; the first word is the ‘genus’ and should be capitalised, and the second word is the ‘species’ which should be featured in lowercase. The entire botanical name should be shown in italics.  

For example; Cedrus atlantica (Atlas Cedarwood) and Juniperus virginiana (Virginian Cedarwood). Or, Eucalyptus globulus and Eucalyptus smithii, belonging to the Myrtaceae family, are different species within the Eucalyptus genus.

Whilst the genus name is always unique, the species name may be associated with more than one genus. E.g. Rosmarinus officinalis, Salvia officinalis. 

To identify a hybrid plant, the genus name is followed by an ‘x’, then the name of the hybrid species e.g. Mentha x piperita, which is a hybrid species from Mentha spicata, spearmint, and Mentha aquatica, water mint (3).

Where an essential oil is obtainable from several species within that a genus, the properties of each species may be significantly different both therapeutically and chemically, and may mean that one species is safer than others in that genus. The Myrtaceae family demonstrates this well, with Eucalyptus smithii being regarded as safe to use in the correct dilutions on children, whilst Eucalyptus dives is not recommended for use on children or in pregnancy.  Subspecies also exist which can sometimes differ in safety and uses. For instance, Ocimum basilicum var. album (Sweet Basil) has a lower percentage of ‘phenolic ethers’ than Ocimum basilicum var. basilicum (Exotic basil) and is, therefore, considered a safer oil to use than the latter because phenols are skin irritants and essential oils containing them should be used with care.  

Synonyms

To further confuse matters botanists sometimes rename plants or use synonyms, and so we may see different names for the same plant on essential oil bottles or in books.  For instance, Anthemis nobilis, commonly known as Roman Chamomile, is also known as Chamomile nobile; it belonged to the Compositae family which was renamed and is now called the Asteraceae family! There are also approximately 30 different synonyms for German Chamomile including Chamomilla recutita, Matricaria recutita and Matricaria chamomilla – the latter being the official name.

Chemotypes or chemovars

Sometimes, an entire plant looks identical so cannot be separated into subspecies, however, numerous variations occur within the chemical constituents and are known as chemotypes or chemovars.  A well-known example of an essential oil with different chemotypes is Thyme oil (Thymus vulgaris).  There are lots of chemical variations within this species, two of which mainly contain a phenol, such as thymol, while the others have an alcohol as the main component, such as linalool.  It is straightforward to identify whether an essential oil is a chemotype as the bottles will be labelled Thymus vulgaris ct. thymol or Thymus vulgaris ct. linalol and their common names will also be derived by their chemotype, for example, those with phenolic components are called Red Thyme, whilst those with alcohol chemical components are called Sweet Thyme.  Other plants also known as chemotypes include Rosemary (Rosmarinus officinalis) which belongs to the Lamiaceae family.  The chemotypes of Rosemary include cineole, camphor-borneoll and verbenone, with the verbenone chemotype being considered as the ‘most gentle and non-irritant’ (3).   It can also be helpful to know the geographical origin of the plant from which the essential oil has been extracted, as this can provide invaluable information about its chemical constituents.

Families can be complicated with plant families being no exception!  I hope this article has helped to demystify the names of essential oils enabling you to choose the right ones, and to practice the wonderful art and science of Aromatherapy safely and effectively.  Next month I will go further into the subject by reviewing an individual plant family and its essential oils in more depth.

In the meantime please visit our website to discover more about our huge range of premium grade essential oils.

Christine Fisk
Consultant Aromatherapist

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Reference List

1. Definition of Family, retrieved from http://www.dictionary.com/ 
2. Plant Families, retrieved from http://theseedsite.co.uk/families.html
3. Battaglia (2007) The Complete Guide to Aromatherapy. 2nd Ed. Australia: The International Centre of Holistic Aromatherapy
4. The Plant List, retrieved from http://www.theplantlist.org/
5. Rosaceae family, retrieved from https://en.wikipedia.org/wiki/Rosaceae