Peony Aroma – Only The Nose Knows Study on smellscape perception and landscape application of fragrant plants.

Song, Xiuhua and Q. Wu. 2021. Urban Forestry and Urban Greening. 67: 127429. 8p.

Plant smell is a combination of low molecular weight volatile compounds released by stems, roots, leaves, flowers, fruits and/or other organs. They can have a positive or negative effect on humans. I think of roseroot, Rhodiola, whose roots have an incredible aroma of roses. Or the flowers of chocolate lily which are smelly and not in a positive way. The word smellscape is used to define the aroma of a location or landscape similar to soundscape in relation to music These authors combined hardcore chemistry using gas chromatography- mass spectroscopy with human perceptions in different garden settings by people walking down a garden path. They studied a variety of flowers, one of which was the woody (tree) peony. Their purpose was to learn how to design outdoor spaces to provide the best fragrance experience for visitors.

Like most flowers, scent is not one compound, but a mixture. For the woody peony, it was a combination of ocimene, citronellol, linalool, 1,3,5-trimethoxybenzene, and pentadecane. The overall fragrance was classed as “woody and light medicinal”. Not very attractive, I’d say! Ocimenes are known as a pleasant odor that is used in perfumes. They are believed to act as  a plant defense and have anti-fungal properties. Citronellol is another pleasant fragrance most commonly associated with oil of roses and geraniums. Linalool has a light fragrant scent used in soaps, fragranes, food additives and insecticides. 1,3,5-trimethoxybenzene has a sweet aromatic odor is combined with other chemicals to be used in colorants. Pentadecane is the main pheromone of the tsetse fly, as well as beetles, mites, fruit flies. What a combination! 

What was interesting in this study was not so much the chemicals but the complexity of studying smell. So many factors are involved, especially when including people. The amount of sunlight, the slighted breeze, air temperature, how fast a person is walking, how far away the flowers are, competing smells from other plants, not to mention the variation among people’s noses and the fact that 5 chemicals are involved. It has to be difficult to make recommendations on landscape design when there are so many variables. Of the five species they studied : Osmanthus, magnolia, wintersweet (Chimonanthus), lilac and woody peonies, the woody peony came in dead last. They recommended that smellscapes be incorporated into viewing routes so when people stop to check out the view, they get the full value of a smellscape!

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