126-The Scentual Garden: Exploring Botanical Fragrance With Ken Druse

What do you think of when you think about your garden? How often do you consider all of the fragrances of the plants in your landscape? Well, this week’s podcast is a celebration of the scentual garden; exploring botanical fragrance, with Ken Druse. Whether subtle or spectacular, plants can emanate fragrance from, not only their blooms, but from foliage and even stems too.

Ken Druse is a notable garden writer with twenty books to his credit. Each one is full of insight for any gardener, but it’s his latest release that really puts the garden into a different perspective. It’s called The Scentual Garden – Exploring the world of botanical fragrance, and from the gorgeous photography to the insightful aromatic descriptions, this book really is a treat for the senses.

Ken’s new book highlighting plant fragrance will bring a new dimension to your garden experience. When was the last time you paused to experience the scent of foliage? (photo: Louis Bauer)

Inspiration

Have you ever noticed that most seed companies and plant catalogs rarely – if ever – mention the fragrance qualities of a plant? Foliage, form, color – these are all important characteristics to help gardeners navigate the sometimes overwhelming array of options. Yet – when you think about it – scent brings a fourth dimension to the garden experience, which is rarely addressed.

If the smell of a plant is ever mentioned, it’s nearly always related only to bloom, and typically says nothing more helpful than “sweet” or “aromatic.” What do those descriptors really even mean? That’s what Ken decided to explore for his latest book.

Ken says his hypersensitivity to scents is both a blessing and a curse, but it has certainly served him well as he describes fragrance in a way that resonates in a way we can all understand. His book is an olfactory exploration of over 100 landscape plants.

Let’s take “sweet” for example. Ken might describe a sweet-smelling flower as honey mixed with spice and lemon rind. Now, that paints a much clearer image in your mind than just “sweet,” right? That level of detail is helpful in deciding if it’s a fragrance that you want to tuck into your landscape, or something that just doesn’t appeal to you.

After all, scent is incredibly suggestive. Not all smells appeal to all of us. Bleach is a good example. Some people find that scent appealing, because it represents clean. There are others of us who, though we are very pro-clean, cringe if we catch a waft of bleach.

Fragrance can pull us in or turn us off. It can also conjure up memories of past experiences, both pleasant and not so much. We’ll get into why that is more in a minute.

Fragrance brings a fourth dimension of interest to the garden. The pink dianthus add a clove scent to the experience of anyone lucky enough to visit the landscape surrounding Ken’s home. (photo: Ken Druse)

Fragrances at Work

Plants don’t give off pleasant fragrances for our personal enjoyment. They have their own, very specific and primal reasons. Some send out an odor to protect themselves from being devoured by wildlife. Yarrow is a good choice if you are looking something deer-resistant because deer usually aren’t hungry enough to tolerate the smell, which they find unpleasant.

Tomato plants will emanate a specific fragrance from their foliage when being attacked by tomato hornworms. The fragrance attracts the braconid wasp, which is a predator of the tomato hornworm caterpillar. The wasp parasitizes and kills the hornworm, which prevents potentially lethal damage to the tomato plant. Pretty fascinating stuff, right?

Here’s another one: Did you know that when a goldenrod plant is under attack from insect pests, it will send out a scent signal to neighboring goldenrods. Essentially, it’s saying “Save yourselves!” – a fragrant warning that the pests are in the area, so the plants should strengthen themselves against attack.

Fragrance from flowers is often designed to attract pollinators. The colors of foliage and flowers will draw in pollinators too, but what about the beneficial insects which are most active at night? The scent of a bloom will travel a long way, day or night, to draw in the creatures that plants requires for reproduction.

There are many flowers which don’t have a scent – or much of one – during the day, but at night, their perfume fills the air. That is in order to attract nocturnal pollinators.

If you’ve ever smelled magnolia blooms, you probably agree that it is a distinctly lemony fragrance. (photo: Ellen Hoverkamp)

The Science of Scent

Fortunately, we get to enjoy the benefit of the various pleasant smells plants emit for survival or reproduction, but have you ever wondered what causes the fragrance in the first place? As Ken puts it, fragrance is actually disintegration of the plant.

Certain molecules within the plant are breaking down as a natural part of the lifecycle. As they disintegrate, they are released into the air. There you have it, fragrance.

We get to enjoy fragrance in many of our modern-day products as a result of analyzation of plant molecules. Lavender is a common scent added to all kinds of products – cleaners, candles, even toilet paper. Most of those items are scented with an artificial – synthesized – reproduction of the natural fragrance of lavender.

In order to synthesize scent, a piece of the plant in question is placed into a machine which analyzes the plant’s compounds at a molecular level. The data collected is then used to mimic the naturally-occurring fragrance.

In roses, the primary component of scent is rose oxide, and it’s a potent one. In fact, humans can detect the smell of rose oxide in as small an amount as 5 parts per billion. That’s hard to wrap your mind around, so Ken uses a time analogy. It’s the equivalent to 5 seconds within a span of 31.7 years.

In spite of the best efforts of science. nature sometimes insists on retaining some of its mystery. Many fragrances are difficult to reproduce accurately. Lilac blooms are made even more precious by the fact that their scent is so short-lived and has never been successfully synthesized. The only way to enjoy the smell of lilac is to get your hands on (or grow) a cluster of actual their blossoms.

There are some perfume and cologne products which are made up of a blend of synthesized fragrances – like synthesized rose and musk. However, some perfumeries do use essential oils captured from plants. According to Ken, it takes about 1,000 jasmine blossoms and 12 centifolia roses to create one ounce of the classic perfume, Chanel No. 5.

How are our favorite natural fragrances incorporated into perfumes and other products? For most scents, the answer is steam. Leaves or flower petals are placed above boiling water. As steam passes through and over the plant material, it rises and, then, condenses to create an essential oil.

Some plants can be expressed or squeezed to produce the essential oil. If you’ve ever pressed on the rind of a citrus fruit, you’ve seen tiny drops of oil burst through the surface of the rind. Other plants release oil in the same way.

The scent of ylang ylang is a common ingredient to bring a musky richness to perfumes and colognes. (photo: Ellen Hoverkamp)

It’s certainly not as elegant, but fragrances are sometimes diluted and captured in oil, carbon dioxide, hexane or dimethyl ether. That might not make your heart skip a beat, but those are all more appealing options than the process that was used hundreds of years ago.

The French used to employ what’s called “enfleurage” – capturing fragrance in animal fat. Flower petals would be lain in a layer of fat spread on a glass sheet within a frame. After one day had passed, the petals would be discarded and new petals placed in the fat. This would go on for two weeks, at which point they would scrape off the scented fat and use wood alcohol to separate fat from essential oil. Ooh la la?

Ken decided to create his own enfleurage experiment. He used the more practical option of vegetable shortening instead of animal fat. After gathering petals of his favorite old rose variety, he placed them into a layer of vegetable shortening, which had melted to an ⅛” thick. After just one night, he removed the petals and stored the shortening in a jar.

Months later, the shortening in the jar still smelled like a rose. So if there is something in your garden you really miss during the cold, dark months of winter; this might be a fun experiment for you too.

The Power of Comparisons

Ken definitely did his homework for this latest book, and he started right in his own backyard. Well actually, his garden is actually situated on his own private, 5-acre island – between two river channels. Nestled in a valley in the northwestern corner of New Jersey, the property only receives a maximum of seven hours of sun each day. So, many of his landscape plants are shade lovers.

Always drawn to fragrance, his landscape provided a lot of plant material from which to start, as Ken began to document scents for the book.

One of the problems when describing fragrance is that there is no recognized standard. Even among experts in the perfume industry, there isn’t a common language used by everyone to describe scents. So as Ken began documenting, he also developed some scent categories to keep things organized.

As you might expect, Ken’s garden is filled with all kinds of fragrant species. (photo: Ken Druse)

By the time it was all said and done, Ken had identified twelve scent categories to group plants which had what he calls “similar fragrance relationships.” Within each category, Ken uses descriptors which are relatable. We all know what a lemon or chocolate smell like. So by describing a fragrance with recognizable terms, it’s easy to understand if the overall scent will be one we will like or be repelled by.

Animalic Scents

The term anamalic is actually used by some in the perfume industry. The root of the word is “animal” – in other words, scents which have some type of animalistic quality. There’s not much subtlety when it comes to this category. Most of these fragrances are obvious – like skunk cabbage, which smells of course like skunk. Fritillaria sounds elegant, but it too smells like skunk.

Ken placed ginkgo into the animalic-scented plants category. Have you ever smelled the fruit of a ginkgo tree? If so, you probably remember it well. It smells like vomit – definitely an animalistic fragrance.

Balsamic Scents

When you think of balsamic vinegar, a very specific smell may come to mind. However, this kitchen ingredient can smell very different, depending on its quality. This category came together as a group of plants which have a scent which is reminiscent of non-coniferous resin. In other words, they don’t have a pine-like scent. These are richer fragrances.

Frankincense and myrrh are examples of plants Ken placed in his balsamic-scented plants category. Other plants in this category feature smells like vanilla and caramel. A sweet quality, but with a kick of pungency and resonance.

Seen here are yellow heliotrope (scented with musk and vanilla) and chestnut blooms, which Ken describes as a fragrance of honey, caramel and smoke. (photo: Ellen Hoverkamp)

Floral Sweet Scents

Let’s call this Ken’s slush category. This was a sort of catch-all for smells which didn’t quite fit into the other eleven categories. Plants Ken categorized as floral-sweet include mock orange and lily of the valley. Interestingly, many plants with floral-sweet smells are the most difficult to synthesize – like lilac.

Forest Scents

These are your plants with a coniferous-type fragrance. Pine trees and rosemary are good examples. Not surprisingly, Ken places juniper into this category and describes its fragrance as being a little sweet, a little cinnamon and a lot of “sharpened pencil.”

Fruity Scents

Freesia and pineapple sage are two examples of the plants which Ken categorizes under the fruity-scented plants category. The smell of these plants is reminiscent of citrus rind or other actual fruits.

Have you ever experienced the fragrance of a deciduous magnolia bloom? It has a definite lemon rind quality to it. Many varieties of the tulip family feature a citrusy scent as well.

Some camelia have a fragrance, and if you’re interested in adding one to your landscape, Ken recommends looking for a variety in the lutchuensis family.

Calycanthus will emit a different smell, depending on variety. For example, Carolina allspice will provide fragrance in the evening, but its scent is interpreted differently by different people. Some think it smells like melon. Others pick up the smell of bubble gum. Calycanthus athens smells like green apple or sometimes honeydew melon.

Ken places some bearded iris varieties into this category, describing their fragrance as grape soda.

The fragrance of brugmansia falls into his Fruity category as lemony. (photo: Ellen Hoverkamp)

Heavy Scents

Plants in this category tend to have a very deep, strong and often complex fragrance. Oriental lilies are renowned for their rich and powerful aroma. Ken describes it as a mix of burnt sugar, vanilla, clove, baby powder, anise, grapefruit, and honey.

Garden phlox isn’t usually noted for its fragrance, but it can give off a strong and complex scent which Ken says includes a note of tobacco.

Ken includes gardenias in the category of heavy scents. It’s among the most fragrant of the flowers in this category. The scent of gardenia is so complex that Ken’s list of descriptors includes jasmine, tuberose, coconut, vanilla, almond, clove, sweet butter, crayons, black pepper, black currant, grass, musk, a touch of cedar, a whisper of patchouli- and indole.

Herbal Green Scents

Many herbs fall into this category in Ken’s book. He says a recurring note throughout the plants in this category is anise. These plants are also reminiscent of green tea, freshly-cut grass or the smell of a recently-broken herbaceous stem.

Some examples of herbal green-scented plants include bee balm and sedge.

Oriental lilies are known for being particularly fragrant. Ken’s sensitive nose picks up a complex blend of clove, honey, paperwhite narcissus, grapefruit, baby powder, and – of all things – cat urine. (photo: Ken Druse)

Honey Scents

Honey is a descriptor that pops up in the scents of plants that Ken placed into other categories. However, the fragrances of plants in this category tend to be rich and syrupy but less complex. They often feature a note of the unexpected and unpleasant – like bleach.

Ken gives the example of flowering privet. Initially, you pick up the smell of honey, but then a bleach-like quality pops in there at some point. Maybe you’re one of those folks who likes the smell of bleach, so privet is right up your alley. As for me, this description helped me to realize exactly why I was so turned off by the smell of privet. It’s a hard pass from me for anything with a noticeable bleachy smell.

Sweet alyssum and black locust fall into the honey scent category. Ken describes the fragrance of hydrangea paniculata as a little honey with an unpleasant quality too, so that landed it into the honey-scents category versus the floral-sweet scents category.

Indolic Scents

Have you ever heard of indole? It’s a compound that is found in all kinds of things – natural and man-made, and it is repugnant. Mothballs, urinal deodorizer cakes, and mold all contain indole.

You know what else has indole in its genetic cocktail? A lot of popular plants do, actually. Hyacinth, jasmine and daffodils are just a few of the many varieties which feature indole. Paperwhite narcissus blooms are gorgeous, but they give off an unpleasant odor, which is largely attributed to indole.

Although indole in and of itself is unpleasant, its fragrance is oftentimes blended with more pleasant scents in the plants we love. Ken describes hyacinth, for example, as a blend of indole and (get this) lilac, mothballs, grass, honey, vanilla, chocolate, and spice.

In other words, the repellency of indole is sometimes made palatable by other enjoyable scents in the mix.

The spectacular blooms of epiphyllum – part of the cactus family – smell like wintergreen. (photo: Ellen Hoverkamp)

Medicinal Scents

Ken considers plants like eucalyptus, wintergreen and artemisia as having a similar medicinal quality. These fragrances tend to have a biting, pungent and – even sometimes – metallic quality. One example he provides in the book is the scent of tomato plant foliage. I happen to love that smell, but when you really think about it, there is a bitter quality mixed in with all that iconic “green” aroma.

There are some bearded iris varieties which have a wintergreen fragrance. Once again, you wouldn’t necessarily say that the smell  of wintergreen is unpleasant, but it certainly can have a bite to it.

Rose Scents

The plants within this category are pretty easy to define. Rose, as a fragrance, is iconic and instantly recognizable. Ken describes it, generally, as baby powder mixed with a little spice. Ironically though, most modern-day rose hybrids don’t have a scent which we can enjoy.

Heirloom roses harken back to the days before hybridization of the species began in 1847. At that time, breeders worked to develop other desirable qualities – like long stems or longevity. Over time, hybridization bred the scent molecules right out of the newly-developed varieties.

There’s been a resurgence in fragrance as a desirable trait, so in recent years, breeders have been creating some varieties expressly for the scent they bring along with all that beauty.

Spice Scents

Some of the plants Ken gathered into this category include purple coneflower. Some of the newly-available varieties of that plant are very fragrant. Ken describes their scent as a blend of orange, cinnamon, clove, and hay.

Viburnum and dianthus or “pinks” (which smell most predominantly like cloves) are additional plants Ken has listed as spice-scented. Ken places geraniums here too. He describes the scent of geranium macrorism as a mix of raisins, cedar, tobacco, and incense.

Unlike many modern-day hybrids, heirloom roses – like this Rosa Petite de Hollande centifolia rose – still carry their fragrance genes. Their scent is unforgettable. (photo: Ken Druse)

Pretty to Look At

It goes without saying that we want the plants in our landscape to be beautiful too, and Ken’s book highlights that aspect of gardening with spectacular photography.

This podcast really wouldn’t have been complete without a discussion about some of the “knocked my socks right off” visuals in the book. If you like botanical prints, you will love the work of photographer Ellen Hoverkamp.

Ellen has mastered the art of photographing plants and flowers using a desktop scanner. She removed the top of the machine, so that she can place the plant materials on the surface to create a very three-dimensional quality.

What she places on the scanner first is, of course, what we see in the foreground of the final image. She layers items to create the final composition. In other words, you could say that she’s working backwards – or upside down. However she does it, it’s working. Her images in the book (like some of those seen here in show notes) will take your breath away.

Ken is a noted garden photographer in his own right. In fact, the Smithsonian Institute invited Ken to share his photography collection to be stored in the Institute’s library for the enjoyment of visitors to that revered organization. Not many of us can say we share in that honor.

Ken describes the scent of peonies as a blend of green mango and minty evergreen. How would you describe them? (photo: Ellen Hoverkamp)

Designing for Fragrance

Once you begin to consider scents – and have a better understanding of what to expect from a certain variety, you’re better able to incorporate what will bring your garden experience to a new level of enjoyment.

The next time you visit someone else’s garden or a local nursery center, make a point of smelling while you look and touch. Smell the foliage. Crush a leaf between your fingers (maybe not appropriate in a public garden, but your friends or a local nursery owner might not mind).

When you do, Ken recommends that – instead of taking deep whiffs – take several short sniffs instead. It turns out that a long, deep inhalation of scent can actually anesthetize you to it. Your sense of smell becomes dulled to its qualities.

It’s common to see dishes of coffee beans offered where perfumes and colognes are available for sale. The beans are meant to cleanse the palette of your nose, but you don’t need to carry any French roast into the garden. Ken recommends that you smell the crook of your elbow instead. He says it’s just as effective for – as he puts it – setting your nose back to the baseline.

As you take in the fragrances of our horticultural world, you might stumble across something that takes you instantly back to a memory from your past. Scent can trigger emotional responses more powerfully than other senses. As it turns out, there’s some science behind that phenomenon.

When odor excites neurons in our nose, an electrical signals travels along nerve cells to the neurons in the olfactory bulb at the base of the front of the brain. That area is what Ken calls the clearinghouse for senses of smell.

From there, odor signals travel into the brain’s higher cortex and the limbic system, which is where emotional feelings are generated and where memories are stored. With memories and fragrance activating the same area of your brain, it’s no wonder scent is such a powerful trigger of our past experiences.

So when you stop to think about it, you could grow pleasant memories of the past right in your own backyard. Now – thanks to Ken’s book – you have a better guide to get you there.

You really don’t want to miss out on this conversation, so if you haven’t already, scroll to the top of the page and click the Play icon in the green bar under the page title. I can’t recommend enough the experience of listening to some of Ken’s descriptions of fragrance in addition to reading them here and in his book.

The scents of lime rind and pine combine in the fragrance of walnut. (photo: Ellen Hoverkamp)

But – before you go – here’s my question to you: What is your favorite garden fragrance and which common terms would you use to describe it to someone else? I’m looking forward to reading what you share in Comments below!

Links & Resources

Episode 068: Top Predatory Beneficial Insects and How to Attract Them, Pt. 2

Episode 119: Deer-Resistant Design: Fence-Free Solutions to Protect the Plants You Love

joegardener Online Academy: Master Pests, Diseases and Weeds – Just $47 for lifetime access! Watch for my new course on seed starting coming soon!

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The Scentual Garden – Exploring the world of botanical fragrance, by Ken Druse

Ellen Hoverkamp