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Fragrance in the Garden
Plant fragrances play an extremely important role in our enjoyment of spending time in a garden or in the Australian bush. Sometimes the fragrances which give us pleasure are subtle and we are almost unaware of their existence or at other times they are as stunning as the most colourful of flowers.
An awareness of Australian plant fragrances will help us to plan our gardens and other plantings so that we can take full advantage of our very important sense of smell.
The involvement of our sense of touch will be well known to anyone who regularly walks past a plant of Prostanthera cuneata, the Alpine Mint Bush, or other species with similarly delightful foliage fragrances. By simply running your hand through the leaves then taking a deep breath there is a magical uplifting sensation, created by this simple yet beautiful fragrance.
Most sections of a plant can be fragrant, with the two major areas being in foliage and floral fragrances. Timber, roots and bark can also emit a range of aromas, which are not necessarily similar to those of the leaves or flowers of the same species.
Many Australian plants are rich in aromatic foliage oils, including eucalypts, melaleucas and tea-trees, all of which are members of the Myrtaceae family. The Rutaceae or Citrus family is another with many aromatic plants including boronias, croweas and eriostemons. The Lamiaceae family includes native menthas (mints) and prostantheras (mint bushes), most of which are strongly aromatic although some can surprise us with their lack of fragrance.
While a small number of these oils are of commercial significance and extracted for various purposes, others give very little oil when distilled even though their fragrance can be readily enjoyed as we brush past plants in the garden or walk on leaves which have dropped to the ground. In several species the foliage fragrance is released into the atmosphere on warm to hot days or by heavy rain and hail.
We will now bring into action our sense of touch and smell, as we feel, crush and enjoy the fragrances of a range of different Australian plants.
Firstly there are several native plants with lemon-scented foliages. These include Eucalyptus citriodora, the Lemon-scented Gum (now Corymbia citriodora, ed), and Eucalyptus staigeriana, the Lemon-scented Ironbark, both of which are native to Queensland. Two tea-trees with lemon-scented leaves are Leptospermum petersoni and L liversidgei.
Callistemon citrinus (NSW, Vic), the Red Bottlebrush, does not have significantly lemon-scented foliage as the species name suggest, and the leaves of Darwinia citriodora (WA) have a fragrance which is more spicy than lemon-like.
One of the most delightful of all lemon-scented foliage plants is Backhousia citriodora (Qld), the Lemon Ironwood or Lemon-scented Myrtle. This is a species which gives a good oil yield when distilled and the foliage can be used in the making of a very pleasant lemon tea.
Boronia citriodora (Tas) and Boronia tetrandra (WA) both have the common name of Lemon-scented Boronia. In B.citriodora this refers to the foliage, while in B.tetrandra it is the light yellow flower-bells which are aromatic. The recently described B.citrata from eastern Victoria also has pungently lemon fragrant foliage.
The "Lemon-scented Myrtle", Backhousia citriodora is a medium sized tree which is native to Queensland rainforests. The foliage has an intense lemon fragrance. Select the thumbnail image or plant name for a higher resolution image (37k).
Lemon-scented Australian grasses include Cymbopogon ambiguus (Qld, NSW, SA, WA and NT), C. procerus (WA, NT) and Elyonurus citreus (Qld, NT).
The classification of different fragrances can be a very complex issue and in foliage fragrances it is most common for the aromas to be described as being similar to others which are already well know to us.
An aniseed fragrance can be found in the leaves of Backhousia anisata (NSW) and Aniseed Tree, and also in Crowea exalata (NSW, Vic), a delightful and variable shrub of around 1 m tall, which displays its starry pink flowers over a long period during late summer and autumn.
Acacia leprosa (NSW, Vic) is commonly known as the Cinnamon Wattle. Backhousia angustifolia (Qld) has a curry aroma, while Polyscias elegans (Qld, NSW), a tree to 30 m tall, is commonly known as Celery Wood because of its particular fragrance.
If you like the smell of camphor, then you can consider planting Baeckea camphorata (Qld, NSW), Baeckea camphorosmae (WA) or Boronia pinnata, all of which are attractive small to medium-sized shrubs.
Although they are members of the Citrus family, correas are not renowned for their foliage fragrances, but have you ever crushed and smelt the leaves of Correa baeuerlenii (NSW), the Chef's Cap Correa. It is a delightful, fruity aroma which reminds many of the days when they were younger and enjoyed Juicy Fruit chewing gum.
The origin of the name "Chefs Cap Correa" is fairly obvious but the flowers of Correa baeuerlenii are not the only attraction of this attractive small shrub. Select the thumbnail image or plant name for a higher resolution image (27k).
Eriostemon myoporoides (Qld, NSW, Vic), in the same family, also has a strong foliage fragrance, enjoyed by many but disliked by some people. It is a fragrance which is more difficult to define as being similar to other well-known aromas. The flowers of this eriostemon have a sweet floral fragrance somewhat like orange blossom.
One of the stronger foliage fragrances is that of mint or peppermint. This is found in several eucalypts including Eucalyptus dives (NSW, Vic) Broad-leaved Peppermint, E.elata (NSW, Vic) River Peppermint, E. nicholii(Qld, NSW) Willow Peppermint, and E.radiata (NSW, Vic) Narrow-leaved Peppermint. There are several Australian species in the genus Mentha and all have strongly aromatic leaves. They are used to a limited extent as a flavouring in cooking, but it is not recommended that they be eaten in the same way as other species of Mentha, commonly referred to as garden mints.
Anyone interested in foliage fragrances is well-advised to check out the entire genus of Prostanthera, commonly known as Mint-bushes. While a few have almost no fragrance at all, the majority are strongly aromatic with a wide range of mint-type fragrances. Prostanthera species usually do not have a high oil yield when distilled but the aromatic water produced is used in aramotherapy. Their delightful fragrances can also give much pleasure to a garden.
Finally we will look at two Australian plants which DO have a high oil yield when the foliage is distilled, with oils of major significance.
Eucalyptus polybractea (NSW, Vic), the Blue-leaved Mallee, is the main species used in the production of Eucalyptus Oil. This oil is highly valued for medicinal, cleaning and lubrication purposes.
Tea-tree Oil is obtained, not from a Leptospermum but from the foliage of Melaleuca alternifolia (Qld, NSW). It is a more costly oil, but one of exceptional medicinal value as an antiseptic for use on cuts and abrasions, as a disinfectant, and for anti-fungal treatment of a range of skin conditions. If you are using Tea-tree oil for the first time it is recommended that it be used in a diluted form, as some people can have an allergic reaction if the oil is used at full strength. Tea-tree oil is worthy of a place in every home first-aid kit, and it has been described as 'a first-aid kit in a bottle' due to its wide range of uses.
It should be pointed out here that not all foliage oils and aromas are as enjoyable as those we have been crushing, smelling and hearing about today. One example is Boronia anemonifolia var. variabilis (Vic, Tas). The foliage has a strong turpentine-like fragrance and must be treated with caution, as prolonged contact with the leaves, particularly in a confined area, can cause headaches or more severe physical discomfort. It could be of course that in years to come this plants may be found to be of major medicinal value when its properties and their uses have been further evaluated.
The second major areas of plant fragrances is in the flowers. Here we find an enormous range of perfumes. Many attempts have been made to classify floral fragrances but there remains difficulty in describing them in a precise way. This is complicated by the fact that our human perception of fragrance varies enormously from person to person. A fragrance which is enticing to one person can be repulsive to another, or you may be simply unable to detect any fragrance at all in a flower which someone else finds strongly aromatic.
Floral perfumes are produced by plants primarily to attract insect pollinators. Many therefore have a sweet, often honey-like fragrance. Some have a caramel or chocolate aroma. Others which are less pleasing to the human nose are those which attract flies and similar insects to what we might regard as an off-putting smell.
You may have noticed that some flowers seem more aromatic in the evening that during the day. Often these are species which are pollinated by moths and other insects which fly and feed mainly at night. Frequently these plants have white, creams or light yellow flowers.
Hymenosporum flavum, the Native Frangipani, is one such species. This adaptable rainforest tree grown naturally in Qld and NSW, but seems just as happy growing and flowering further south, in Victoria. It must have protection from frosts when plants are young. During late spring and early summer there is an abundant display of delightfully fragrant flowers which are initially cream then change as they age to yellow then deep gold. Fragrant oils which incorporate or replicated the fragrance of this species are now readily available.
It should be mentioned here that floral fragrance are not as easy to extract as foliage oils. The flowers are available only during the flowering period and harvesting is not nearly as easy as cutting branches of leaves for distilling. Pure floral oils are therefore extremely expensive, and in nearly all cases the Australian floral oils offered for retail sale are compounded rather than essential oils. When available in concentrated form the oil produced by normally delightfully fragrant flowers can be overpowering and unattractive.
The most renowned of all fragrant Australian plants is Boronia megastigma (WA) the Brown Boronia. Plants are cultivated in various areas of the world for their fragrance and also for the cut flower trade. The suburb of Boronia, east of Melbourne, received its name from the extensive plantings of Boronia megastigma, most of which have now been replaced by residential development. Many people find B.megastigma a difficult plant to maintain in cultivation, the main reason being that plants do not survive if the soil around the root system becomes dry, even for a relatively short period. A well-drained but moist situation is essential. Plants also respond well to pruning, so are ideally suited to cut flower use. There are many other boronias with fragrant flowers, but none share the unique perfume of Boronia megastigma.
The flowers of "Brown Boronia", Boronia megastigma are usually dull brown in colour on the outside and bright yellow within. They make up for their lack of flair with a magnificent fragrance. This is the cultivar "Harlequin" one of several colour forms in cultivation. Select the thumbnail image or plant name for a higher resolution image (32k).
A floral fragrance which appears to be better known overseas than in Australia is that of some of our wattles, commonly known as mimosas in Europe. Plants are cultivated for use in the perfumeries of southern France, and species grown include Acacia dealbata (NSW, Vic, Tas), Silver Wattle. A farnesiana, which can be seen growing in Qld, NSW, WA, SA, NT is also cultivated for its fragrant flowers. This has been regarded as an Australian species, but it also occurs in America, Africa and Asia and it is now though that plants may have been introduced here prior to white settlement.
Some genera which are well-known throughout the world for their floral fragrances and also have species which are native to Australia include Gardenia, Hoya, Jasminum, Kailarsenia (includes species recently transferred from Gardenia), Randia, a range of different orchids, plus species of Alpinia and other native gingers.
Moving from gingers to additional fragrances which excite our taste-buds, we find chocolate or caramel fragrances in the flowers of Arthropodium strictus (previously Dichopogon strictus) Chocolate Lily, which occurs in all states and A.milleflorum, a dainty lily from Qld, NSW, Vic, Tas and SA. Other plants with similar fragrance include species and varieties of Eremaea including E.beaufortioides and E.ebracteata (WA), and Grevillea species including G.polybotrya (WA).
Some flowers are not as enticing, including several which belong to the Proteaceae family. Banksia media and B.praemorsa (both from WA) have flower-spikes which smell somewhat like meat pies (perhaps a little past their 'use-by' date) and the fragrance of Persoonia flowers can be less than pleasant on a warm to hot day. Grevillea leucopteris (WA) is not called Smelly Socks for nothing, and Hakea denticulata, formerly H.rubriflora (WA) is even more off-putting. The attractive flowers of Hibbertia scandens and Tetratheca thymifolia can have a fragrance which is less than enjoyable.
It is not possible to cover the many perfumed and aromatic Australian plants here, but hopefully you may be encouraged to delve further into this fascinating aspect of our flora. It can certainly add a new dimension of pleasure to gardening and bush walks. There are still many fragrances yet to be discovered by us all.
Fragrant Australian Plants
The following list provides a selection of the many Australian plants noted for their pleasantly fragrant foliage and/or flowers.
Acacia leprosa, A.redolens
Backhousia angustifolia, B.citriodora
Baeckea camphorata, B.camphorosmae, B.citriodora and other species
Boronia citriodora, B.pinnata, B.safrolifera and other species
Chamelaucium ciliatum, C."hamatum"
Cymbopogon ambiguus, C.procerus
Darwinia citriodora, D.diosmoides, D.nieldiana, D.pinifolia
Eucalyptus cephalocarpa, E.citriodora, E.crenulata, E.dives, E.elata, E.glaucescens, E.globulus, E.nicholii, E.odorata, E.polyanthemos, E.polybractea, E.pulchella, E.radiata, E.staigeriana, E.viminalis, E.viridis and other species
Hypocalymma angustifolium, H.myrtifolium
Leptospermum liversidgei, L.petersonii
Melaleuca alternifolia, M.calothamnoides, M.erubescens, M.leucadendra, M.pulchella, M.quinquenervia
Mentha australis, M.diemenica, M.laxiflora
Phebalium bilobum, P.glandulosum, P.lamprophyllum, P.squamulosum
Plectranthus argentatus, P.graveolens, P.parviflorus
Prostanthera aspalathoides, P.cineolifera, P.cuneata, P.incisa, P.lasianthos, P.melissifolia, P.ovalifolia, P.rotundifolia, P.violacea and many other species
Thryptomene calycina, T.saxicola
Veticordia densiflora, V.monodelpha, V.plumosa
Zieria cytisioides, Z.veronicea
Acacia dealbata, A.suaveolens and many other species
Alocasia brisbanensis (syn A.macrorrhizos)
Arthropodium milleflorum, A.strictus
Boronia clavata, B.floribunda, B.fraseri, B.heterophylla, B.megastigma, B.muelleri, B.purdieana, B.serrulata, B.tetrandra
Cassia brewsteri, C.nemophila
Clerodendron floribundum, C.inerme
Crinum flaccidum, C.pedunculatum and other species
Cymbidium madidum, C.suave
Dendrobium falcorostrum, D.speciosum, D.tetragonum and other species
Eremaea beaufortioides, E.ebracteata, E.phoenicea
Eucryphia lucida, E.moorei
Gardenia megasperma and other species
Hoya australis and other species
Jasminum lineare, J.suavissimum and other species
Kailarsenia jardinei, K.ochreata, K.suffruticosa
Pittosporum revolutum, P.rhombifolium, P.undulatum
Prostanthera lasianthos, P.striatiflora
Pultenaea graveolens, P.hartmannii
Randia audasii, R.benthamiana, R.fitzalanii and other species
Sarcochilus falcatus, S.hartmannii, S.fitzgeraldii and other species
Scaevola crassifolia and other species
This article is a reproduction of a paper presented by Gwen at the SGAP 18th Biennial Seminar held at Ballarat, Victoria from 23 to 29 September 1995.
Gwen has been an active member of SGAP for about 30 years. Her first book, entitled "Australian Plants for Small Gardens and Containers" was first published in 1979 and remains in print in a revised and updated edition today. She has since written seven further books covering Australian plants, their cultivation, identification and uses.
With her husband Rodger, she has travelled widely within Australia and overseas, their interest in Australian plants being the focal point of most journeys.
Gwen is a frequent lecturer and radio broadcaster on Australian plants and is an Honorary Life Member of SGAP Victoria.
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