SMELLS LIKE... - INFO

smell
 SMELLS LIKE

If you can identify the particular odour of which the flowers smell, or of the leaves when they are crushed or the stem bruised, then this may help identification.

But beware! Some plants exude a toxic substance when the stem is broken or the leaves are crushed. In particular: The milky sap from Spurges, euphorbia, is harmful on contact with the skin. The sap from both Hogweed and Giant Hogweed can cause wheals on the skin after exposure to sunlight. Monkshood should never be touched; there is no antidote to its highly toxic nerve poison which can enter the skin by touch. The sap from Rhus trees is also injurious to tissue. This is not an exhaustive list.

But smells are very difficult to classify, especially the perfumy ones, so I'm not sure how much this category will help, but it is a fun thing to insert.

Some pungent smells may be classified under foetid, putrid, billy goat, mousy, nauseous, evil or tom-cat. Take your pick. If unsure, look up each category.

As you may understand, it is utterly pointless entering Roses under the heading 'Smells Like Roses', so I have avoided this pitfall.

Flowers that are scented particularly fragrantly are entered under Very Fragrant & Perfumy.

There have been numerous attempts at classifying smells over the decades. It was once assumed that if a chemical had much the same shape as another chemical, it would smell similar, for they would dock with the same olfactory receptors, triggering a response in nerve cells. But this was found not to be the case. There are many instances of substances smelling similar but have quite different chemical structures. Another theory is that the characteristic vibrational frequencies of substances that smell the same have the same resonant frequency. But this is not true in all cases either.

It has been found empirically that if a molecule contains more than about 18 atoms of carbon, then it will be odourless (although the converse is not true). This is not due to any lack of volatility of molecules with 19 or more carbon atoms, since even on heating an odourless 19-carbon molecule will still be odourless. Also, as a rule of thumb, molecules with fewer than 8 atoms of carbon are, if they are odorous, are usually only feebly odorous. There are, of course, exceptions.

Odour is very subjective and variable, depending upon the presence or absence of hundreds of differing smell sensors in the nose. Few folk possess all the sensors, many have disparate sensors absent. As a result differing people either report the same compound as smelling differently or cannot smell it at all; what is pleasant to some may be repugnant or even aromaless to others - a friend of the Authors' reports Hedge Woundwort as smelling rather nice!

If anyone knows of any plant that smells of something else, then please write in, and I'll put it in here.

It is possible to search this website for a plant with a specific small. For instance, to search for a plant that smells of aniseed type 'smells?aniseed' (without any spaces) into the search string.

WHY FLOWERS SMELL

The plants themselves manufacture the chemicals that are responsible for their odours, both foul or pleasant to humans.

But the plants don't make smells to please humans. The smells are there to either attract certain insects who might do the plant some good (such as pollinators) or to repel other insects who might do the plant harm (like eat it).

It has recently been proved that, in the case of Petunias, the pleasant (to humans) scented smells of isoeugenol and benzyl benzoate actively discourage some insects from eating much of the blossom. There are probably many more chemical/insect interactions, both attractive and repellent, that are yet to be discovered in the many differing odorous chemicals manufactured by disparate plants.

There are also plant-signalling molecules that travel between plants, both like and un-like plants, by various means, through the soil and through the air. Both methods are a means of communication between plants. These molecules warn other plants of impending threats, such as injury by pests or disease, etc. It could be said that the molecules travelling by air are being 'smelled' by other plants (even though they may or may not be detectable by humans). Likewise, for those molecules travelling via the soil, it could be said that the other plants 'taste' them.



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